redis plus plus
redis-plus-plus 1.3.13
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Eu crio um módulo Redis, chamado Redis-llm, que integra LLMS (grandes modelos de idiomas) com Redis. Você pode aprender Redis-plus-plus fazendo perguntas com ele.
Esta é uma biblioteca de clientes C ++ para Redis. É baseado em Hiredis e é compatível com C ++ 17, C ++ 14 e C ++ 11.
Nota : Eu não sou um falante nativo. Portanto, se a documentação não estiver clara, sinta -se à vontade para abrir uma solicitação de problema ou puxar. Vou responder o mais rápido possível.
A filial principal é o ramo estável, que passa todos os testes. O ramo de dev é instável. Se você deseja contribuir, crie uma solicitação de puxar no Dev Branch.
Como o Redis-plus-plus é baseado no Hiredis , você deve instalar o Hiredis primeiro. O requisito mínimo da versão para o Hiredis é v0.12.1 . No entanto, é sempre recomendável o último lançamento estável do Hiredis .
NOTA : Você deve garantir que haja apenas 1 versão do Hiredis. Caso contrário, você pode ter alguns problemas com fio. Verifique os seguintes problemas, por exemplo: Edição 135, edição 140 e Edição 158.
Normalmente, você pode instalar o Hiredis com um gerenciador de pacotes C ++, e essa é a maneira mais fácil de fazê-lo, por exemplo sudo apt-get install libhiredis-dev . No entanto, se você deseja instalar o código mais recente do Hiredis, ou uma versão especificada (por exemplo, o ASYNC SUPORTE precisa de Hiredis v1.0.0 ou posterior), você pode instalá -lo na fonte.
Nota novamente: não instale várias versões do Hiredis.
git clone https://github.com/redis/hiredis.git
cd hiredis
make
make installPor padrão, o Hiredis está instalado em /usr /local . Se você deseja instalar o Hiredis no local não padrão, use os seguintes comandos para especificar o caminho da instalação.
make PREFIX=/non/default/path
make PREFIX=/non/default/path installRedis-plus-plus é construído com cmake.
git clone https://github.com/sewenew/redis-plus-plus.git
cd redis-plus-plus
mkdir build
cd build
cmake ..
make
make install
cd .. Se o Hiredis estiver instalado no local não padrão, você deverá usar CMAKE_PREFIX_PATH para especificar o caminho de instalação do Hiredis . Por padrão, o Redis-plus-plus está instalado em /usr /local . No entanto, você pode usar CMAKE_INSTALL_PREFIX para instalar o Redis-plus-plus no local sem defesa.
cmake -DCMAKE_PREFIX_PATH=/path/to/hiredis -DCMAKE_INSTALL_PREFIX=/path/to/install/redis-plus-plus .. Desde a versão 1.3.0, por padrão, o Redis-plus-plus é construído com o padrão -std=c++17 . Para que possamos usar os recursos STD :: String_View e STD :: Opcional. No entanto, ele também pode ser criado com o padrão -std=c++11 ou -std=c++14 e, nesse caso, temos nossa própria implementação simples de std::string_view e std::optional . Para especificar explicitamente o padrão C ++, você pode usar o seguinte sinalizador CMake: -DREDIS_PLUS_PLUS_CXX_STANDARD=11 .
cmake -DCMAKE_PREFIX_PATH=/path/to/hiredis -DCMAKE_INSTALL_PREFIX=/path/to/install/redis-plus-plus -DREDIS_PLUS_PLUS_CXX_STANDARD=11 ..NOTA : Você deve criar o Redis-plus-plus e seu aplicativo com o mesmo padrão, por exemplo, se você criar redis-plus-plus com o padrão C ++ 17, você também deve criar seu código de aplicativo com o padrão C ++ 17.
Ao compilar Redis-plus-plus , ele também compila um programa de teste, o que pode demorar um pouco. No entanto, você pode desativar o teste de construção com a seguinte opção cmake: -DREDIS_PLUS_PLUS_BUILD_TEST=OFF .
cmake -DCMAKE_PREFIX_PATH=/path/to/hiredis -DCMAKE_INSTALL_PREFIX=/path/to/install/redis-plus-plus -DREDIS_PLUS_PLUS_BUILD_TEST=OFF .. Por padrão, o Redis-plus-plus constrói uma biblioteca estática e uma biblioteca compartilhada. Se você deseja criar apenas um deles, poderá desativar o outro com -DREDIS_PLUS_PLUS_BUILD_STATIC=OFF ou -DREDIS_PLUS_PLUS_BUILD_SHARED=OFF .
Redis-plus-plus compra biblioteca estática com opção -fPIC , ou seja, código independente, por padrão. No entanto, você pode desativá -lo com -DREDIS_PLUS_PLUS_BUILD_STATIC_WITH_PIC=OFF .
Agora a contratada tem suporte ao Windows e, desde o Visual Studio 2017, o Visual Studio tem suporte integrado ao CMake. Portanto, o Redis-plus-plus também suporta o Windows Platform agora. Ele foi totalmente testado com o Visual Studio 2017 e mais tarde no Win 10. Não estou familiarizado com o ambiente do Visual Studio, e o documento a seguir pode não ser preciso. Se você estiver familiarizado com a plataforma Windows, sinta-se à vontade para atualizar este documento sobre como instalar o Redis-plus-plus no Windows.
A seguir, alguns links sobre como criar o CMake Project com o Visual Studio 2017 ou posterior. Se você não estiver familiarizado com isso, é melhor ler estas instruções primeiro:
NOTA : O IMHO, o suporte do Visual Studio 2017 para o CMake Project não é muito maduro, e eu recomendo que você construa Hiredis e *Redis-plus-plus com o Visual Studio 2019.
Primeiro de tudo, você precisa obter o código mais recente do Hiredis no Master Branch. A versão mais antiga pode não suportar a plataforma Windows. O Cmakelists.txt de Hiredis usa o método add_compile_definitions , que é suportado apenas pelo CMake 3.12 ou posterior. No entanto, a versão CMake do Visual Studio 2017 é mais antiga que isso. Portanto, se você estiver usando o Visual Studio 2017, precisará comentar a seguinte linha no arquivo cmakelists.txt:
#IF(WIN32)
# ADD_COMPILE_DEFINITIONS(_CRT_SECURE_NO_WARNINGS WIN32_LEAN_AND_MEAN)
#ENDIF()Você pode usar o recurso de pasta aberta para abrir o projeto Hiredis e construí -lo com as instruções (links) mencionadas acima.
Como o Redis-plus-plus depende do Hiredis , precisamos especificar os caminhos de instalação do Hiredis antes de construí-lo. Você pode usar o recurso de pasta aberta para abrir o projeto Redis-plus-plus . Você precisa editar o arquivo cmakesetting.json (gerado automaticamente pelo Visual Studio) para definir variáveis Hiredis_Header , Hiredis_lib e Test_hiredis_lib para especificar o caminho de instalação dos cabeçalhos Hiredis, o caminho de instalação do caminho da biblioteca dinâmica de Hiredis e do caminho de instalação da biblioteca estática de Hiredis. A seguir, é apresentado um exemplo de arquivo cmakesetting.json :
{
"configurations" : [
{
"name" : " x64-Release " ,
"generator" : " Visual Studio 15 2017 Win64 " ,
"configurationType" : " Release " ,
"buildRoot" : " ${env.LOCALAPPDATA} \ CMakeBuild \ ${workspaceHash} \ build \ ${name} " ,
"cmakeCommandArgs" : " " ,
"buildCommandArgs" : " -m -v:minimal " ,
"variables" : [
{
"name" : " HIREDIS_HEADER " ,
"value" : " installation path of hiredis header files " ,
"type" : " PATH "
},
{
"name" : " HIREDIS_LIB " ,
"value" : " installation path of dynamic library of hiredis " ,
"type" : " FILEPATH "
},
{
"name" : " TEST_HIREDIS_LIB " ,
"value" : " installation path of static library of hiredis " ,
"type" : " FILEPATH "
}
]
}
]
} Em seguida, você pode construir as instruções (links) mencionadas acima. Se você estiver construindo com o Visual Studio 2017 no modo de depuração, poderá receber o erro /bigobj ao criar o teste. Nesse caso, você pode desativar o teste de construção definindo -DREDIS_PLUS_PLUS_BUILD_TEST=OFF ou construí -lo no modo de liberação.
OBSERVAÇÃO :
REDIS_PLUS_PLUS_CXX_STANDARD CMake como 11.Se você deseja construir o projeto com o Visual Studio e tiver dúvidas, siga as etapas abaixo. O seguinte é testado na comunidade Visual Studio 2022.
# download two projects into this folder
mkdir redis ++
cd redis ++
# make sure you create a hiredis first to work as a library
mkdir hiredis - lib
cd hiredis - lib
mkdir lib
git clone https: // github.com / redis / hiredis.git
cd hiredis Até agora, deve ficar bem a cada etapa. Em seguida, abra o arquivo CMakeLists.txt . Modifique a seguinte linha e comente
...
# SET(CMAKE_DEBUG_POSTFIX d)
...Em seguida, volte para a pasta do projeto Hiredis
mkdir build
cd build
# convert project into visual studio 2022, if necessary choose you version e.g 19 2019 etc.
cmake - G " Visual Studio 17 2022 " ..
. / hiredis.sln Set hiredis como projeto de inicialização e clique em Build Solution no modo de depuração
Após a construção bem-sucedida, copie todos os arquivos sob Debug na pasta hiredis-lib/lib
Aqui, o trabalho para Hiredis deve ser concluído.
Em seguida, volte para a pasta redis++ . Terminal aberto aqui
git clone https: // github.com / sewenew / redis - plus - plus.git
cd redis - plus - plus
mkdir build
cd build Agora você deve sempre ter OpenSSL no seu PC, caso contrário, pode usar o Chocolatey para instalá -lo. Para o Visual Studio 2022, instale o pthread separadamente usando vpckg , seguindo este link
Depois de toda a preparação. Se você deseja converter todos os projetos, então
cmake - DCMAKE_PREFIX_PATH = " $ ( ABSOLUTE_PATH ) hiredis-lib " - G " Visual Studio 17 2022 " ..
cd build
. / redis ++ .sln Defina redis++_static como projeto de inicialização e clique em Build Solution
Até agora, a construção foi concluída com sucesso!
Na plataforma Windows, se o código do seu aplicativo também precisar incluir Windows.h . Você deve garantir que SW/Redis ++/Redis ++. H esteja incluído antes do Windows.h . Verifique este problema para obter detalhes.
O suporte básico para a construção de um pacote GNU/Debian é fornecido com o uso do CMake. O exemplo a seguir mostra como construir o pacote Debian:
mkdir build ; cd build
cmake ..
cpack -G DEBO prefixo de instalação pode ser modificado da seguinte forma:
mkdir build ; cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr ..
cpack -G DEBRedis-plus-plus foi totalmente testado com os seguintes compiladores:
gcc version 4.8.5 20150623 (Red Hat 4.8.5-39) (GCC)
gcc version 5.5.0 20171010 (Ubuntu 5.5.0-12ubuntu1)
gcc version 6.5.0 20181026 (Ubuntu 6.5.0-2ubuntu1~18.04)
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
gcc version 8.3.0 (Ubuntu 8.3.0-6ubuntu1~18.04.1)
gcc version 9.2.1 20191008 (Ubuntu 9.2.1-9ubuntu2)
gcc version 10.2.1 20210110 (Debian 10.2.1-6)
clang version 3.9.1-19ubuntu1 (tags/RELEASE_391/rc2)
clang version 4.0.1-10 (tags/RELEASE_401/final)
clang version 5.0.1-4 (tags/RELEASE_501/final)
clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
clang version 7.0.0-3~ubuntu0.18.04.1 (tags/RELEASE_700/final)
clang version 8.0.1-3build1 (tags/RELEASE_801/final)
Apple clang version 11.0.0 (clang-1100.0.33.12)
Visual Studio 2017 (Win 10)
Visual Studio 2019 (Win 10) Se você criar redis -plus -plus com -DREDIS_PLUS_PLUS_BUILD_TEST=ON (o comportamento padrão, e poderá desativar o teste de construção com -DREDIS_PLUS_PLUS_BUILD_TEST=OFF ), obterá um programa de teste no diretório de compilação/teste : Build/Test/Test_redis ++ .
Para executar os testes, você precisa configurar uma instância Redis e um cluster Redis. Como o programa de teste enviará a maioria dos comandos Redis para o servidor e o cluster, você precisa configurar o Redis da versão mais recente. Caso contrário, os testes podem falhar. Por exemplo, se você configurar o Redis 4.0 para teste, o programa de teste falhará quando tentar enviar o comando ZPOPMAX (um comando Redis 5.0) para o servidor. Se você deseja executar os testes com outras versões Redis, deve comentar comandos que não foram suportados pelo seu Redis, a partir de arquivos de origem de teste no diretório Redis-plus-plus/test/src/sw/redis ++/ . Desculpe pelo inconveniente e resolverei esse problema para fazer com que o programa de teste funcione com qualquer versão do Redis no futuro.
Nota : A versão mais recente do Redis é apenas um requisito para executar os testes. De fato, você pode usar o Redis-plus-plus com Redis de qualquer versão, ou seja, Redis 2.0 e acima.
Nunca execute o programa de teste em invenção de produção, uma vez que as chaves, que o programa de teste lê ou escreve, podem entrar em conflito com seu aplicativo.
Para executar testes com Redis e Redis Cluster, você pode executar o programa de teste com o seguinte comando:
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_portSe você deseja executar apenas testes com o Redis, só precisará especificar opções de host , porta e autenticação :
./build/test/test_redis++ -h host -p port -a authDa mesma forma, se você deseja executar apenas testes com o Redis Cluster, basta especificar opções de cluster_node , cluster_port e auth :
./build/test/test_redis++ -a auth -n cluster_node -c cluster_portPor padrão, o programa de teste não testará executando o Redis-plus-plus em um ambiente de vários threads. Se você deseja fazer o teste de vários threads, que pode custar muito tempo, pode especificar a opção -m :
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_port -mSe todos os testes foram aprovados, o programa de teste imprimirá a seguinte mensagem:
Pass all testsCaso contrário, ele imprime a mensagem de erro.
Redis-plus-plus funciona tão rápido quanto Hiredis , já que é um invólucro de Hiredis . Você pode executar test_redis ++ no modo de referência para verificar o desempenho em seu ambiente.
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_port -b -t thread_num -s connection_pool_size -r request_num -k key_len -v val_len10 por padrão.5 por padrão.100000 por padrão.10 por padrão.10 por padrão. O Bechmark gerará 100 chaves binárias aleatórias para teste, e o tamanho dessas teclas é especificado por key_len . Quando o benchmark for executado, ele lerá/gravará com essas chaves. Portanto, nunca execute o programa de teste em seu ambiente de produção; caso contrário, ele poderá excluir com inacabilidade seus dados.
Depois de compilar o código, você obterá biblioteca compartilhada e biblioteca estática. Como o Redis-plus-plus depende do Hiredis , você precisa vincular as duas bibliotecas ao seu aplicativo. Também não se esqueça de especificar o padrão C ++, -std=c++17 , -std=c++14 ou -std=c++11 , bem como a opção relacionada ao encadeamento.
Tome o GCC como exemplo.
g++ -std=c++17 -o app app.cpp /path/to/libredis++.a /path/to/libhiredis.a -pthread Se Hiredis e Redis-plus-plus estiverem instalados no local não-defensor, você deve usar -I opção para especificar o caminho do cabeçalho.
g++ -std=c++17 -I/non-default/install/include/path -o app app.cpp /path/to/libredis++.a /path/to/libhiredis.a -pthreadg++ -std=c++17 -o app app.cpp -lredis++ -lhiredis -pthread Se Hiredis e Redis-plus-plus estiverem instalados no local não-padrão, você deve usar as opções -I e -L para especificar os caminhos de cabeçalho e biblioteca.
g++ -std=c++17 -I/non-default/install/include/path -L/non-default/install/lib/path -o app app.cpp -lredis++ -lhiredis -pthreadAo vincular -se a bibliotecas compartilhadas e executar seu aplicativo, você pode receber a seguinte mensagem de erro:
error while loading shared libraries: xxx: cannot open shared object file: No such file or directory. Isso porque o vinculador não consegue encontrar as bibliotecas compartilhadas. Para resolver o problema, você pode adicionar o caminho em que instalou as bibliotecas Hiredis e Redis-plus-plus , à variável de ambiente LD_LIBRARY_PATH . Por exemplo:
export LD_LIBRARY_PATH= $LD_LIBRARY_PATH :/usr/local/libVerifique esta pergunta do StackOverflow para obter detalhes sobre como resolver o problema.
Se você estiver usando o CMake para criar seu aplicativo, precisará adicionar dependências Hiredis e Redis-plus-plus em seus cmakelists.txt :
# <---------- set c++ standard ------------->
# NOTE: you must build redis-plus-plus and your application code with the same standard.
set (CMAKE_CXX_STANDARD 17)
set (CMAKE_CXX_STANDARD_REQUIRED ON )
# <------------ add hiredis dependency --------------->
find_path (HIREDIS_HEADER hiredis)
target_include_directories ( target PUBLIC ${HIREDIS_HEADER} )
find_library (HIREDIS_LIB hiredis)
target_link_libraries ( target ${HIREDIS_LIB} )
# <------------ add redis-plus-plus dependency -------------->
# NOTE: this should be *sw* NOT *redis++*
find_path (REDIS_PLUS_PLUS_HEADER sw)
target_include_directories ( target PUBLIC ${REDIS_PLUS_PLUS_HEADER} )
find_library (REDIS_PLUS_PLUS_LIB redis++)
target_link_libraries ( target ${REDIS_PLUS_PLUS_LIB} )Veja este problema para obter um exemplo completo de cmakelists.txt .
Além disso, se você instalou o Hiredis e o Redis-plus-plus no local não padrão, precisará executar o Cmake com a opção CMAKE_PREFIX_PATH para especificar o caminho de instalação dessas duas bibliotecas.
cmake -DCMAKE_PREFIX_PATH=/installation/path/to/the/two/libs ..
# include < sw/redis++/redis++.h >
using namespace sw ::redis ;
try {
// Create an Redis object, which is movable but NOT copyable.
auto redis = Redis ( " tcp://127.0.0.1:6379 " );
// ***** STRING commands *****
redis. set ( " key " , " val " );
auto val = redis. get ( " key " ); // val is of type OptionalString. See 'API Reference' section for details.
if (val) {
// Dereference val to get the returned value of std::string type.
std::cout << *val << std::endl;
} // else key doesn't exist.
// ***** LIST commands *****
// std::vector<std::string> to Redis LIST.
std::vector<std::string> vec = { " a " , " b " , " c " };
redis. rpush ( " list " , vec. begin (), vec. end ());
// std::initializer_list to Redis LIST.
redis. rpush ( " list " , { " a " , " b " , " c " });
// Redis LIST to std::vector<std::string>.
vec. clear ();
redis. lrange ( " list " , 0 , - 1 , std::back_inserter (vec));
// ***** HASH commands *****
redis. hset ( " hash " , " field " , " val " );
// Another way to do the same job.
redis. hset ( " hash " , std::make_pair ( " field " , " val " ));
// std::unordered_map<std::string, std::string> to Redis HASH.
std::unordered_map<std::string, std::string> m = {
{ " field1 " , " val1 " },
{ " field2 " , " val2 " }
};
redis. hmset ( " hash " , m. begin (), m. end ());
// Redis HASH to std::unordered_map<std::string, std::string>.
m. clear ();
redis. hgetall ( " hash " , std::inserter (m, m. begin ()));
// Get value only.
// NOTE: since field might NOT exist, so we need to parse it to OptionalString.
std::vector<OptionalString> vals;
redis. hmget ( " hash " , { " field1 " , " field2 " }, std::back_inserter (vals));
// ***** SET commands *****
redis. sadd ( " set " , " m1 " );
// std::unordered_set<std::string> to Redis SET.
std::unordered_set<std::string> set = { " m2 " , " m3 " };
redis. sadd ( " set " , set. begin (), set. end ());
// std::initializer_list to Redis SET.
redis. sadd ( " set " , { " m2 " , " m3 " });
// Redis SET to std::unordered_set<std::string>.
set. clear ();
redis. smembers ( " set " , std::inserter (set, set. begin ()));
if (redis. sismember ( " set " , " m1 " )) {
std::cout << " m1 exists " << std::endl;
} // else NOT exist.
// ***** SORTED SET commands *****
redis. zadd ( " sorted_set " , " m1 " , 1.3 );
// std::unordered_map<std::string, double> to Redis SORTED SET.
std::unordered_map<std::string, double > scores = {
{ " m2 " , 2.3 },
{ " m3 " , 4.5 }
};
redis. zadd ( " sorted_set " , scores. begin (), scores. end ());
// Redis SORTED SET to std::vector<std::pair<std::string, double>>.
// NOTE: The return results of zrangebyscore are ordered, if you save the results
// in to `std::unordered_map<std::string, double>`, you'll lose the order.
std::vector<std::pair<std::string, double >> zset_result;
redis. zrangebyscore ( " sorted_set " ,
UnboundedInterval< double >{}, // (-inf, +inf)
std::back_inserter (zset_result));
// Only get member names:
// pass an inserter of std::vector<std::string> type as output parameter.
std::vector<std::string> without_score;
redis. zrangebyscore ( " sorted_set " ,
BoundedInterval< double >( 1.5 , 3.4 , BoundType::CLOSED), // [1.5, 3.4]
std::back_inserter (without_score));
// Get both member names and scores:
// pass an back_inserter of std::vector<std::pair<std::string, double>> as output parameter.
std::vector<std::pair<std::string, double >> with_score;
redis. zrangebyscore ( " sorted_set " ,
BoundedInterval< double >( 1.5 , 3.4 , BoundType::LEFT_OPEN), // (1.5, 3.4]
std::back_inserter (with_score));
// ***** SCRIPTING commands *****
// Script returns a single element.
auto num = redis. eval < long long >( " return 1 " , {}, {});
// Script returns an array of elements.
std::vector<std::string> nums;
redis. eval ( " return {ARGV[1], ARGV[2]} " , {}, { " 1 " , " 2 " }, std::back_inserter (nums));
// mset with TTL
auto mset_with_ttl_script = R"(
local len = #KEYS
if (len == 0 or len + 1 ~= #ARGV) then return 0 end
local ttl = tonumber(ARGV[len + 1])
if (not ttl or ttl <= 0) then return 0 end
for i = 1, len do redis.call("SET", KEYS[i], ARGV[i], "EX", ttl) end
return 1
)" ;
// Set multiple key-value pairs with TTL of 60 seconds.
auto keys = { " key1 " , " key2 " , " key3 " };
std::vector<std::string> args = { " val1 " , " val2 " , " val3 " , " 60 " };
redis. eval < long long >(mset_with_ttl_script, keys. begin (), keys. end (), args. begin (), args. end ());
// ***** Pipeline *****
// Create a pipeline.
auto pipe = redis. pipeline ();
// Send mulitple commands and get all replies.
auto pipe_replies = pipe . set ( " key " , " value " )
. get ( " key " )
. rename ( " key " , " new-key " )
. rpush ( " list " , { " a " , " b " , " c " })
. lrange ( " list " , 0 , - 1 )
. exec ();
// Parse reply with reply type and index.
auto set_cmd_result = pipe_replies. get < bool >( 0 );
auto get_cmd_result = pipe_replies. get <OptionalString>( 1 );
// rename command result
pipe_replies. get < void >( 2 );
auto rpush_cmd_result = pipe_replies. get < long long >( 3 );
std::vector<std::string> lrange_cmd_result;
pipe_replies. get ( 4 , back_inserter (lrange_cmd_result));
// ***** Transaction *****
// Create a transaction.
auto tx = redis. transaction ();
// Run multiple commands in a transaction, and get all replies.
auto tx_replies = tx. incr ( " num0 " )
. incr ( " num1 " )
. mget ({ " num0 " , " num1 " })
. exec ();
// Parse reply with reply type and index.
auto incr_result0 = tx_replies. get < long long >( 0 );
auto incr_result1 = tx_replies. get < long long >( 1 );
std::vector<OptionalString> mget_cmd_result;
tx_replies. get ( 2 , back_inserter (mget_cmd_result));
// ***** Generic Command Interface *****
// There's no *Redis::client_getname* interface.
// But you can use *Redis::command* to get the client name.
val = redis. command <OptionalString>( " client " , " getname " );
if (val) {
std::cout << *val << std::endl;
}
// Same as above.
auto getname_cmd_str = { " client " , " getname " };
val = redis. command <OptionalString>(getname_cmd_str. begin (), getname_cmd_str. end ());
// There's no *Redis::sort* interface.
// But you can use *Redis::command* to send sort the list.
std::vector<std::string> sorted_list;
redis. command ( " sort " , " list " , " ALPHA " , std::back_inserter (sorted_list));
// Another *Redis::command* to do the same work.
auto sort_cmd_str = { " sort " , " list " , " ALPHA " };
redis. command (sort_cmd_str. begin (), sort_cmd_str. end (), std::back_inserter (sorted_list));
// ***** Redis Cluster *****
// Create a RedisCluster object, which is movable but NOT copyable.
auto redis_cluster = RedisCluster ( " tcp://127.0.0.1:7000 " );
// RedisCluster has similar interfaces as Redis.
redis_cluster. set ( " key " , " value " );
val = redis_cluster. get ( " key " );
if (val) {
std::cout << *val << std::endl;
} // else key doesn't exist.
// Keys with hash-tag.
redis_cluster. set ( " key{tag}1 " , " val1 " );
redis_cluster. set ( " key{tag}2 " , " val2 " );
redis_cluster. set ( " key{tag}3 " , " val3 " );
std::vector<OptionalString> hash_tag_res;
redis_cluster. mget ({ " key{tag}1 " , " key{tag}2 " , " key{tag}3 " },
std::back_inserter (hash_tag_res));
} catch ( const Error &e) {
// Error handling.
}Você também pode ver Redis.H para documentação no estilo doxygen.
A classe Redis mantém um pool de conexão para o Redis Server. Se a conexão estiver quebrada, Redis se reconectará ao servidor Redis automaticamente.
Você pode inicializar uma instância Redis com ConnectionOptions e ConnectionPoolOptions . ConnectionOptions especifica as opções para a conexão com o servidor Redis, e ConnectionPoolOptions especifica as opções para o Conneciton Pool. ConnectionPoolOptions é opcional. Se não for especificado, Redis mantém uma única conexão com o servidor Redis.
ConnectionOptions connection_options;
connection_options.host = " 127.0.0.1 " ; // Required.
connection_options.port = 6666 ; // Optional. The default port is 6379.
connection_options.password = " auth " ; // Optional. No password by default.
connection_options.db = 1 ; // Optional. Use the 0th database by default.
// Optional. Timeout before we successfully send request to or receive response from redis.
// By default, the timeout is 0ms, i.e. never timeout and block until we send or receive successfuly.
// NOTE: if any command is timed out, we throw a TimeoutError exception.
connection_options.socket_timeout = std::chrono::milliseconds( 200 );
// Connect to Redis server with a single connection.
Redis redis1 (connection_options);
ConnectionPoolOptions pool_options;
pool_options.size = 3 ; // Pool size, i.e. max number of connections.
// Optional. Max time to wait for a connection. 0ms by default, which means wait forever.
// Say, the pool size is 3, while 4 threds try to fetch the connection, one of them will be blocked.
pool_options.wait_timeout = std::chrono::milliseconds( 100 );
// Optional. Max lifetime of a connection. 0ms by default, which means never expire the connection.
// If the connection has been created for a long time, i.e. more than `connection_lifetime`,
// it will be expired and reconnected.
pool_options.connection_lifetime = std::chrono::minutes( 10 );
// Connect to Redis server with a connection pool.
Redis redis2 (connection_options, pool_options); Nota : Se você definir ConnectionOptions::socket_timeout e tente chamar comandos de bloqueio, por exemplo, Redis::brpop , Redis::blpop , Redis::bzpopmax , Redis::bzpopmin , você deve garantir que ConnectionOptions::socket_timeout seja maior que o timeout especificado com os comandos em forma. Caso contrário, você pode obter TimeoutError e perder mensagens.
Consulte ConnectionOptions e ConnectionPoolOptions para obter mais opções. Consulte também a edição 80 para discussão no pool de conexões.
Nota : a classe Redis é móvel, mas não é copável.
// auto redis3 = redis1; // this won't compile.
// But it's movable.
auto redis3 = std::move(redis1);Redis-plus-plus também suporta conectar-se ao servidor Redis com o soquete do Domain Unix.
ConnectionOptions options;
options.type = ConnectionType::UNIX;
options.path = " /path/to/socket " ;
Redis redis (options);Você também pode se conectar ao servidor Redis com um URI:
tcp://[[username:]password@]host[:port][/db]
redis://[[username:]password@]host[:port][/db]
unix://[[username:]password@]path-to-unix-domain-socket[/db]
O esquema e as peças do host são necessários e outras são opcionais. Se você estiver se conectando ao Redis com o soquete do UNIX Domain, use o esquema UNIX ; caso contrário, use o esquema TCP ou Redis . A seguir, é apresentada uma lista de valores padrão para essas peças opcionais:
Nota : Se sua senha ou nome de usuário contiver '@' ou seu nome de usuário contiver ':', você não poderá construir Redis Object com URI. Porque Redis-plus-plus analisará incorretamente o URI. Nesse caso, você precisa usar ConnectionOptions para construir o objeto Redis .
Nota : O Redis 6.0 suporta ACL e você pode especificar um nome de usuário para a conexão. No entanto, antes do Redis 6.0, você não pode fazer isso.
Além disso, as seguintes opções de conexão e opções de pool de conexão podem ser especificadas com a sequência de consulta de URI, por exemplo, TCP: //127.0.0.1? Keep_alive = true & socket_timeout = 100ms & Connect_timeout = 100ms :
| Opção | Parâmetro | Padrão |
|---|---|---|
ConnectionOptions::user | usuário | padrão |
ConnectionOptions::password | senha | string vazia, ou seja, sem senha |
ConnectionOptions::db | dB | 0 |
ConnectionOptions::keep_alive | Keep_alive | falso |
ConnectionOptions::connect_timeout | Connect_timeout | 0ms |
ConnectionOptions::socket_timeout | Socket_timeout | 0ms |
ConnectionOptions::resp | resp | 2 |
ConnectionPoolOptions::size | pool_size | 1 |
ConnectionPoolOptions::wait_timeout | pool_wait_timeout | 0ms |
ConnectionPoolOptions::connection_lifetime | pool_connection_lifetime | 0ms |
ConnectionPoolOptions::connection_idle_time | pool_connection_idle_time | 0ms |
OBSERVAÇÃO :
// Single connection to the given host and port.
Redis redis1 ( " tcp://127.0.0.1:6666 " );
// Use default port, i.e. 6379.
Redis redis2 ( " tcp://127.0.0.1 " );
// Connect to Redis with password, and default port.
Redis redis3 ( " tcp://[email protected] " );
// Connect to Redis and select the 2nd (db number starts from 0) database.
Redis redis4 ( " tcp://127.0.0.1:6379/2 " );
// Set keep_alive option to true with query string.
Redis redis5 ( " tcp://127.0.0.1:6379/2?keep_alive=true " );
// Set socket_timeout to 50 milliseconds, and connect_timeout to 1 second with query string.
Redis redis6 ( " tcp://127.0.0.1?socket_timeout=50ms&connect_timeout=1s " );
// Connect to Unix Domain Socket.
Redis redis7 ( " unix://path/to/socket " ); Desde o Redis 6.0, ele suporta uma nova versão do Protocolo Redis, ou seja, resp3. Para usar este novo protocolo, você precisa definir ConnectionOptions::resp ser 3.
ConnectionOptions opts;
opts.resp = 3;
// Set other options...
Por padrão, ConnectionOptions::resp IS 2, ou seja, use a RESP versão 2. Até agora, apenas as versão 2 e 3 são suportadas e o comportamento é indefinido, se você definir ConnectionOptions::resp como outros números.
NOTA : Para usar este novo protocolo, você precisa instalar os mais recentes Hiredis (mesmo o Hiredis-V1.0.2 possui bugs no suporte resp3).
As conexões na piscina são criadas preguiçosamente. Quando o pool de conexões é inicializado, ou seja, o construtor do Redis , Redis não se conecta ao servidor. Em vez disso, ele se conecta ao servidor somente quando você tenta enviar comando. Dessa forma, podemos evitar conexões desnecessárias. Portanto, se o tamanho da piscina for 5, mas o número de conexões simultâneas máximas for 3, haverá apenas 3 conexões na piscina.
Você não precisa verificar se o objeto Redis se conecta ao servidor com sucesso. Se Redis não conseguir criar uma conexão com o servidor Redis, ou a conexão estiver quebrada em algum momento, ela lança uma exceção do tipo de Error ao tenta enviar comando com Redis . Mesmo quando você obtém uma exceção, ou seja, a conexão está quebrada, você não precisa criar um novo objeto Redis . Você pode reutilizar o objeto Redis para enviar comandos, e o objeto Redis tentará se reconectar ao servidor automaticamente. Se ele se reconectar com sucesso, enviará comando para o servidor. Caso contrário, ele lança uma exceção novamente.
Consulte a seção de exceção para obter detalhes sobre exceções.
Não é barato criar um objeto Redis , pois criará novas conexões com o servidor Redis. Então, é melhor você reutilizar o objeto Redis o máximo possível. Além disso, é seguro chamar as funções de membro da Redis em ambiente de múltiplos thread e você pode compartilhar o objeto Redis em vários threads.
// This is GOOD practice.
auto redis = Redis( " tcp://127.0.0.1 " );
for ( auto idx = 0 ; idx < 100 ; ++idx) {
// Reuse the Redis object in the loop.
redis. set ( " key " , " val " );
}
// This is VERY BAD! It's very inefficient.
// NEVER DO IT!!!
for ( auto idx = 0 ; idx < 100 ; ++idx) {
// Create a new Redis object for each iteration.
auto redis = Redis ( " tcp://127.0.0.1 " );
redis. set ( " key " , " val " );
}Redis-plus-plus também possui suporte ao TLS. No entanto, para usar esse recurso, você precisa habilitá-lo ao criar Hiredis e Redis-plus-plus .
Nota : Até agora, o recurso TLS não foi testado na plataforma Windows. Vou consertar isso no futuro.
Ao construir o Hiredis com suporte ao TLS, você precisa baixar o Hiredis da versão v1.0.0 ou o posto e especificar USE_SSL=1 sinalizador:
make PREFIX=/non/default/path USE_SSL=1
make PREFIX=/non/default/path USE_SSL=1 install Em seguida, você pode criar o Redis-plus-plus para ativar o suporte TLS especificando o -DREDIS_PLUS_PLUS_USE_TLS=ON opção:
cmake -DREDIS_PLUS_PLUS_USE_TLS=ON ..Para se conectar ao Redis com o suporte ao TLS, você precisa especificar as seguintes opções de conexão:
ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
opts.tls.enabled = true ; // Required. `false` by default.
opts.tls.cert = " /path/to/client/certificate " ; // Optional
opts.tls.key = " /path/to/private/key/file " ; // Optional
opts.tls.cacert = " /path/to/CA/certificate/file " ; // You can also set `opts.tls.cacertdir` instead.
opts.tls.sni = " server-name-indication " ; // Optional Embora tls.cert e tls.key sejam opcionais, se você especificar um deles, também deve especificar o outro. Em vez de especificar tls.cacert , você também pode especificar tls.cacertdir para o diretório onde os certificados são armazenados.
Essas opções são as mesmas que os argumentos da linha de comando relacionados ao TLS do redis-cli , para que você também possa executar redis-cli --help para obter a explicação detalhada dessas opções.
Em seguida, você pode usar essas ConnectionOptions para criar um objeto Redis para se conectar ao servidor Redis com o suporte TLS.
Nota : Ao criar o código do seu aplicativo, você também precisa vinculá -lo com libhiredis.a , libhiredis_ssl.a , libredis++.a (ou as bibliotecas compartilhadas correspondentes), -lssl e -lcrypto .
Por padrão, o Redis-plus-plus inicializa automaticamente a biblioteca OpenSSL, ou seja, chama SSL_library_init e inicializa os bloqueios, se necessário. No entanto, o código do seu aplicativo já pode inicializar a biblioteca OpenSSL. Nesse caso, você pode ligar para tls::disable_auto_init() para desativar a inicialização. Você deve chamar essa função apenas uma vez e chamá-la antes de qualquer outra operação Redis-plus-plus . Caso contrário, o comportamento é indefinido.
Desde que a Hiredis v1.1.0, ele suporta a verificação de certificado de pular. Se você deseja usar esse recurso com o Redis-plus-plus , pode verificar esse problema para um exemplo.
Você pode enviar comandos Redis através do objeto Redis . Redis possui um ou mais métodos (sobrecarregados) para cada comando redis. O método tem o mesmo nome (inferior) que o comando correspondente. Por exemplo, temos 3 métodos de sobrecarga para o comando DEL key [key ...]
// Delete a single key.
long long Redis::del ( const StringView &key);
// Delete a batch of keys: [first, last).
template < typename Input>
long long Redis::del (Input first, Input last);
// Delete keys in the initializer_list.
template < typename T>
long long Redis::del (std::initializer_list<T> il);Com os parâmetros de entrada, esses métodos criam um comando redis com base no protocolo Redis e enviam o comando para o servidor Redis. Em seguida, receba a resposta de maneira síncrona, analise -a e retorne ao chamador.
Vamos dar uma olhada nos parâmetros desses métodos e retornar valores.
A maioria desses métodos possui os mesmos parâmetros que os comandos correspondentes. A seguir, é apresentada uma lista de tipos de parâmetros:
| Tipo de parâmetro | Explicação | Exemplo | Observação |
|---|---|---|---|
| StringView | Parâmetros do tipo String. Normalmente usado para chave, valor, nome do membro, nome de campo e assim por diante | bool redis :: hset (const stringview & key, const stringview & field, const stringview e val) | Veja a seção StringView para obter detalhes sobre StringView |
| longo longo | Parâmetros do tipo inteiro. Normalmente usado para índice (por exemplo, comandos de lista) ou inteiro | Void LTRIM (const StringView & Key, Longa Start Longa, longa parada longa) Longo Decfrby (const StringView & Key, Longo Longo Diminuir) | |
| dobro | Parâmetros do tipo de ponto flutuante. Normalmente usado para pontuação (por exemplo, comandos de conjunto classificado) ou número de tipo de ponto flutuante | Double Incrbyfloat (const StringView & Key, Double Increment) | |
| std :: crono :: duração std :: crono :: time_point | Parâmetros relacionados ao tempo | Bool Expire (const StringView & Key, const std :: crono :: segundos & timeout) BOOL EXPIREAT (const StringView & Key, const std :: crono :: time_point <std :: crono :: system_clock, std :: crono :: segundos> & tp) | |
| std :: par <stringview, stringview> | Utilizado para o par de hash (campo, valor) de Redis (Valor) | BOOL HSET (const StringView & Key, const std :: par <stringview, stringview> & item) | |
| std :: par <duplo, duplo> | Utilizado para o par de Redis Geo (longitude, latitude) | OptionAllongLong Georadius (const StringView & Key, const std :: par <duplo, duplo> e localização, raio duplo, unidade geounit, const stringview & destino, bool store_dist, contagem longa) | |
| par de iteradores | Use um par de iteradores para especificar uma variedade de entrada, para que possamos passar os dados em um contêiner STL para esses métodos | Modelo <nome do tipo de tipo Longo Del (entrada primeiro, entrada por último) | Faça uma exceção, se for um alcance vazio, ou seja, primeiro == último |
| std :: Initializer_list <T> | Use uma lista de inicializador para especificar um lote de entrada | Modelo <nome do tipo T> Long Long Del (std :: Initializer_list <T> il) | |
| Algumas opções | Opções para alguns comandos | UpdateType , modelo <nome do tipo T> Classe BoundedInterval | Veja command_options.h para obter detalhes |
STD :: String_View é uma boa opção para os tipos de parâmetros de string somente leitura. std::string_view foi introduzido apenas no padrão C ++ 17; portanto, se você construir Redis -plus -plus com o -std=c++11 (ou seja, especificando -DREDIS_PLUS_PLUS_CXX_STANDARD=11 com comando cmake) ou o -std=c++14 StringView , uma implementação simples de std::string_view Você pode criar Redis-plus-plus com o padrão -std=c++17 (ou seja, o comportamento padrão), que fornecerá std::string_view nativamente. A implementação StringView será desconsiderada, aliasando -a ao std::string_view . Isso é feito dentro da biblioteca Redis-plus-plus com: using StringView = std::string_view .
Como existem conversões de std::string e String no estilo C para StringView , você pode simplesmente passar std::string ou String no estilo C para métodos que precisam de um parâmetro StringView .
// bool Redis::hset(const StringView &key, const StringView &field, const StringView &val)
// Pass c-style string to StringView.
redis.hset( " key " , " field " , " value " );
// Pass std::string to StringView.
std::string key = " key " ;
std::string field = " field " ;
std::string val = " val " ;
redis.hset(key, field, val);
// Mix std::string and c-style string.
redis.hset(key, field, " value " );Redis Protocol define 5 tipos de respostas:
long long . Além disso, essas respostas podem ser nulas . Por exemplo, quando você tenta GET o valor de uma chave inexistente, o Redis retorna uma resposta de sequência em massa nula .
Como mencionamos acima, as respostas são analisadas nos valores de retorno desses métodos. A seguir, é apresentada uma lista de tipos de devolução:
| Tipo de retorno | Explicação | Exemplo | Observação |
|---|---|---|---|
| vazio | Resposta de status que sempre deve retornar uma sequência de "ok" | Renomear , setex | |
| std :: string | Resposta de status que nem sempre retorna "ok" e resposta em massa | Ping , informação | |
| bool | Resposta inteira que sempre retorna 0 ou 1 | Expire , hset | Veja a seção de valor de retorno booleano para o significado de um valor de retorno booleano |
| longo longo | Responder inteiro que nem sempre retorna 0 ou 1 | Del , anexar | |
| dobro | Resposta em massa que representa um duplo | Incrbyfloat , zincby | |
| std :: par | Resposta da matriz com exatamente 2 elementos. Como o valor de retorno é sempre uma matriz de 2 elementos, retornamos os 2 elementos como um primeiro e segundo elementos de std::pair | BLPOP | |
| std :: tupla | Resposta da matriz com comprimento fixo e possui mais de 2 elementos. Como a duração da matriz retornada é fixa, retornamos a matriz como uma std::tuple | BZPOPMAX | |
| Iterador de saída | Resposta geral da matriz com comprimento não fixado/dinâmico. Usamos a interface do tipo STL para retornar esse tipo de matriz, para que você possa inserir o valor de retorno em um contêiner STL facilmente | MGET , LRANGE | Além disso, às vezes o tipo de iterador de saída decide quais opções enviar com o comando. Veja a seção Exemplos para obter detalhes |
| Opcional <T> | Para qualquer resposta do tipo T que possa ser nula | Get , LPOP , BLPOP , BZPOPMAX | Veja a seção opcional para obter detalhes sobre Optional<T> |
| Variante <args ...> | Para resposta, isso pode ser de diferentes tipos diferentes | Estatísticas de memória | Nota: Até agora, esse tipo é suportado apenas ao compilar Redis-plus-plus com o padrão C ++ 17. Isso é normalmente usado com interface de comando genérico. Veja a seção Variante para obter detalhes sobre Variant<Args...> |
| Contêiner STL | Resposta geral da matriz | Config Get | O iterador de saída e o contêiner STL são usados para resposta da matriz. A diferença é que o contêiner STL é normalmente usado com interface de comando genérico. Veja a seção de contêiner STL, por exemplo, |
O tipo de retorno de alguns métodos, por exemplo, EXPIRE , HSET , é bool . Se o método retornar false , isso não significa que Redis não enviou o comando para o servidor Redis. Em vez disso, isso significa que o servidor Redis retorna uma resposta inteira e o valor da resposta é 0 . Consequentemente, se o método retornar true , significa que o servidor Redis retorna uma resposta inteira e o valor da resposta é 1 . Você pode verificar o Manual dos Comandos Redis para o que 0 e 1 representam.
Por exemplo, quando enviamos o comando EXPIRE para o Redis Server, ele retorna 1 se o tempo limite foi definido e retornará 0 se a chave não existir. Consequentemente, se o tempo limite foi definido, Redis::expire retorna true e, se a chave não existir, Redis::expire retorna false .
Portanto, nunca use o valor de retorno para verificar se o comando foi enviado com sucesso ao Redis Server. Em vez disso, se Redis falhou ao enviar comando para o servidor, ele lançará uma exceção do Error de tipo. Consulte a seção de exceção para obter detalhes sobre exceções.
STD :: Opcional é uma boa opção para o tipo de retorno, se Redis puder retornar a resposta nula . No entanto, std::optional é introduzido no padrão C ++ 17 e, se você criar Redis -plus -plus com -std=c++11 padrão (ou seja, especificando -DREDIS_PLUS_PLUS_CXX_STANDARD=11 com o comando cmake), implementamos nossa própria versão simples, Ie template Optional<T> . Em vez disso, se você criar redis-plus-plus com -std=c++17 padrão (ou seja, o comportamento padrão), você poderá usar std::optional e temos um alias para isso: template <typename T> using Optional = std::optional<T> .
Veja os comandos GET e MGET, por exemplo:
// Or just: auto val = redis.get("key");
Optional<std::string> val = redis.get( " key " );
// Optional<T> has a conversion to bool.
// If it's NOT a null Optional<T> object, it's converted to true.
// Otherwise, it's converted to false.
if (val) {
// Key exists. Dereference val to get the string result.
std::cout << *val << std::endl;
} else {
// Redis server returns a NULL Bulk String Reply.
// It's invalid to dereference a null Optional<T> object.
std::cout << " key doesn't exist. " << std::endl;
}
std::vector<Optional<std::string>> values;
redis.mget({ " key1 " , " key2 " , " key3 " }, std::back_inserter(values));
for ( const auto &val : values) {
if (val) {
// Key exist, process the value.
}
} Também temos alguns typedefs para algumas Optional<T> :
using OptionalString = Optional<std::string>;
using OptionalLongLong = Optional< long long >;
using OptionalDouble = Optional< double >;
using OptionalStringPair = Optional<std::pair<std::string, std::string>>; STD :: Variant é uma boa opção para o tipo de retorno, se a resposta pode ser de tipos diferentes. Por exemplo, o comando MEMORY STATS retorna uma resposta da matriz, que é, de fato, um mapa de pares de configurações de valor-chave:
127.0.0.1: 6379> memory stats
1) " peak.allocated "
2) (integer) 4471104
...
17) " db.0 "
18) 1) " overhead.hashtable.main "
2) (integer) 104
3) " overhead.hashtable.expires "
4) (integer) 32
...
27) " dataset.percentage "
28) " 9.70208740234375 "
... No entanto, como você pode ver, a parte do valor do resultado pode ser de longa duração (chave: pico.alocada ), dupla (chave: DataSet.Percentage ) ou mesmo um mapa (chave: db.0 ). Portanto, você não pode simplesmente analisar o resultado em um std::unordered_map<std::string, long long> ou std::unordered_map<std::string, double> . Uma solução alternativa é analisar o resultado em uma tuple , no entanto, essa solução de tupla é feia e propensa a erros. Verifique este problema para obter detalhes.
Nesse caso, Variant , que é um typedef de std::variant se você criar redis-plus-plus com c ++ 17 padrão, é muito útil. Você pode analisar o resultado em um std::unordered_map<std::string, Variant<double, long long, std::unordered_map<std::string, long long>>> .
using Var = Variant< double , long long , std::unordered_map<std::string, long long >>;
auto r = Redis( " tcp://127.0.0.1 " );
auto v = r.command<std::unordered_map<std::string, Var>>( " memory " , " stats " ); Existem algumas limitações no suporte Variant :
Variant não podem ter itens duplicados, por exemplo, Variant<double, long long, double> não funciona.double deve ser colocado antes std::string . Como a resposta double é, de fato, a resposta da string e, ao analisar a variante, tentamos analisar a resposta no primeiro tipo correspondente, especificado com os argumentos de tipo da esquerda para a direita. Portanto, se double for colocado após std::string , ou seja, no lado direito do std::string , a resposta sempre será analisada no std::string .Verifique também a seção de comando genérico para obter mais exemplos na interface de comando genérico.
Ao usar a interface de comando genérico, em vez de analisar a resposta ao iterador de saída, você também pode analisá -lo em um contêiner STL.
auto r = Redis( " tcp://127.0.0.1 " );
auto v = r.command<std::unordered_map<std::string, std::string>>( " config " , " get " , " * " );Verifique também a seção de comando genérico para obter mais exemplos na interface de comando genérico.
Vamos ver alguns exemplos sobre como enviar comandos para o Redis Server.
// ***** Parameters of StringView type *****
// Implicitly construct StringView with c-style string.
redis.set( " key " , " value " );
// Implicitly construct StringView with std::string.
std::string key ( " key " );
std::string val ( " value " );
redis.set(key, val);
// Explicitly pass StringView as parameter.
std::vector< char > large_data;
// Avoid copying.
redis.set( " key " , StringView(large_data.data(), large_data.size()));
// ***** Parameters of long long type *****
// For index.
redis.bitcount(key, 1 , 3 );
// For number.
redis.incrby( " num " , 100 );
// ***** Parameters of double type *****
// For score.
redis.zadd( " zset " , " m1 " , 2.5 );
redis.zadd( " zset " , " m2 " , 3.5 );
redis.zadd( " zset " , " m3 " , 5 );
// For (longitude, latitude).
redis.geoadd( " geo " , std::make_tuple( " member " , 13.5 , 15.6 ));
// ***** Time-related parameters *****
using namespace std ::chrono ;
redis.expire(key, seconds( 1000 ));
auto tp = time_point_cast<seconds>(system_clock::now() + seconds( 100 ));
redis.expireat(key, tp);
// ***** Some options for commands *****
if (redis.set(key, " value " , milliseconds( 100 ), UpdateType::NOT_EXIST)) {
std::cout << " set OK " << std::endl;
}
redis.linsert( " list " , InsertPosition::BEFORE, " pivot " , " val " );
std::vector<std::string> res;
// (-inf, inf)
redis.zrangebyscore( " zset " , UnboundedInterval< double >{}, std::back_inserter(res));
// [3, 6]
redis.zrangebyscore( " zset " ,
BoundedInterval< double >( 3 , 6 , BoundType::CLOSED),
std::back_inserter (res));
// (3, 6]
redis.zrangebyscore( " zset " ,
BoundedInterval< double >( 3 , 6 , BoundType::LEFT_OPEN),
std::back_inserter (res));
// (3, 6)
redis.zrangebyscore( " zset " ,
BoundedInterval< double >( 3 , 6 , BoundType::OPEN),
std::back_inserter (res));
// [3, 6)
redis.zrangebyscore( " zset " ,
BoundedInterval< double >( 3 , 6 , BoundType::RIGHT_OPEN),
std::back_inserter (res));
// [3, +inf)
redis.zrangebyscore( " zset " ,
LeftBoundedInterval< double >( 3 , BoundType::RIGHT_OPEN),
std::back_inserter (res));
// (3, +inf)
redis.zrangebyscore( " zset " ,
LeftBoundedInterval< double >( 3 , BoundType::OPEN),
std::back_inserter (res));
// (-inf, 6]
redis.zrangebyscore( " zset " ,
RightBoundedInterval< double >( 6 , BoundType::LEFT_OPEN),
std::back_inserter (res));
// (-inf, 6)
redis.zrangebyscore( " zset " ,
RightBoundedInterval< double >( 6 , BoundType::OPEN),
std::back_inserter (res));
// ***** Pair of iterators *****
std::vector<std::pair<std::string, std::string>> kvs = {{ " k1 " , " v1 " }, { " k2 " , " v2 " }, { " k3 " , " v3 " }};
redis.mset(kvs.begin(), kvs.end());
std::unordered_map<std::string, std::string> kv_map = {{ " k1 " , " v1 " }, { " k2 " , " v2 " }, { " k3 " , " v3 " }};
redis.mset(kv_map.begin(), kv_map.end());
std::unordered_map<std::string, std::string> str_map = {{ " f1 " , " v1 " }, { " f2 " , " v2 " }, { " f3 " , " v3 " }};
redis.hmset( " hash " , str_map.begin(), str_map.end());
std::unordered_map<std::string, double > score_map = {{ " m1 " , 20 }, { " m2 " , 12.5 }, { " m3 " , 3.14 }};
redis.zadd( " zset " , score_map.begin(), score_map.end());
std::vector<std::string> keys = { " k1 " , " k2 " , " k3 " };
redis.del(keys.begin(), keys.end());
// ***** Parameters of initializer_list type *****
redis.mset({
std::make_pair ( " k1 " , " v1 " ),
std::make_pair ( " k2 " , " v2 " ),
std::make_pair ( " k3 " , " v3 " )
});
redis.hmset( " hash " ,
{
std::make_pair ( " f1 " , " v1 " ),
std::make_pair ( " f2 " , " v2 " ),
std::make_pair ( " f3 " , " v3 " )
});
redis.zadd( " zset " ,
{
std::make_pair ( " m1 " , 20.0 ),
std::make_pair ( " m2 " , 34.5 ),
std::make_pair ( " m3 " , 23.4 )
});
redis.del({ " k1 " , " k2 " , " k3 " }); // ***** Return void *****
redis.save();
// ***** Return std::string *****
auto info = redis.info();
// ***** Return bool *****
if (!redis.expire( " nonexistent " , std::chrono::seconds( 100 ))) {
std::cerr << " key doesn't exist " << std::endl;
}
if (redis.setnx( " key " , " val " )) {
std::cout << " set OK " << std::endl;
}
// ***** Return long long *****
auto len = redis.strlen( " key " );
auto num = redis.del({ " a " , " b " , " c " });
num = redis.incr( " a " );
// ***** Return double *****
auto real = redis.incrbyfloat( " b " , 23.4 );
real = redis.hincrbyfloat( " c " , " f " , 34.5 );
// ***** Return Optional<std::string>, i.e. OptionalString *****
auto os = redis.get( " kk " );
if (os) {
std::cout << *os << std::endl;
} else {
std::cerr << " key doesn't exist " << std::endl;
}
os = redis.spop( " set " );
if (os) {
std::cout << *os << std::endl;
} else {
std::cerr << " set is empty " << std::endl;
}
// ***** Return Optional<long long>, i.e. OptionalLongLong *****
auto oll = redis.zrank( " zset " , " mem " );
if (oll) {
std::cout << " rank is " << *oll << std::endl;
} else {
std::cerr << " member doesn't exist " << std::endl;
}
// ***** Return Optional<double>, i.e. OptionalDouble *****
auto ob = redis.zscore( " zset " , " m1 " );
if (ob) {
std::cout << " score is " << *ob << std::endl;
} else {
std::cerr << " member doesn't exist " << std::endl;
}
// ***** Return Optional<pair<string, string>> *****
auto op = redis.blpop({ " list1 " , " list2 " }, std::chrono::seconds( 2 ));
if (op) {
std::cout << " key is " << op-> first << " , value is " << op-> second << std::endl;
} else {
std::cerr << " timeout " << std::endl;
}
// ***** Output iterators *****
std::vector<OptionalString> os_vec;
redis.mget({ " k1 " , " k2 " , " k3 " }, std::back_inserter(os_vec));
std::vector<std::string> s_vec;
redis.lrange( " list " , 0 , - 1 , std::back_inserter(s_vec));
std::unordered_map<std::string, std::string> hash;
redis.hgetall( " hash " , std::inserter(hash, hash.end()));
// You can also save the result in a vecotr of string pair.
std::vector<std::pair<std::string, std::string>> hash_vec;
redis.hgetall( " hash " , std::back_inserter(hash_vec));
std::unordered_set<std::string> str_set;
redis.smembers( " s1 " , std::inserter(str_set, str_set.end()));
// You can also save the result in a vecotr of string.
s_vec.clear();
redis.smembers( " s1 " , std::back_inserter(s_vec));sw::redis::Cursor cursor = 0 ;
auto pattern = " *pattern* " ;
auto count = 5 ;
std::unordered_set<std::string> keys;
while ( true ) {
cursor = redis. scan (cursor, pattern, count, std::inserter (keys, keys. begin ()));
// Default pattern is "*", and default count is 10
// cursor = redis.scan(cursor, std::inserter(keys, keys.begin()));
if (cursor == 0 ) {
break ;
}
}Às vezes, o tipo de iterador de saída decide quais opções enviar com o comando.
// If the output iterator is an iterator of a container of string,
// we send *ZRANGE* command without the *WITHSCORES* option.
std::vector<std::string> members;
redis.zrange( " list " , 0 , - 1 , std::back_inserter(members));
// If it's an iterator of a container of a <string, double> pair,
// we send *ZRANGE* command with *WITHSCORES* option.
std::vector<std::pair<std::string, double >> res_with_score;
redis.zrange( " list " , 0 , - 1 , std::back_inserter(res_with_score));
// The above examples also apply to other command with the *WITHSCORES* options,
// e.g. *ZRANGEBYSCORE*, *ZREVRANGE*, *ZREVRANGEBYSCORE*.
// Another example is the *GEORADIUS* command.
// Only get members.
members.clear();
redis.georadius( " geo " ,
std::make_pair ( 10.1 , 11.1 ),
100,
GeoUnit::KM,
10,
true,
std::back_inserter(members));
// If the iterator is an iterator of a container of tuple<string, double>,
// we send the *GEORADIUS* command with *WITHDIST* option.
std::vector<std::tuple<std::string, double >> mem_with_dist;
redis.georadius( " geo " ,
std::make_pair ( 10.1 , 11.1 ),
100,
GeoUnit::KM,
10,
true,
std::back_inserter(mem_with_dist));
// If the iterator is an iterator of a container of tuple<string, double, string>,
// we send the *GEORADIUS* command with *WITHDIST* and *WITHHASH* options.
std::vector<std::tuple<std::string, double , std::string>> mem_with_dist_hash;
redis.georadius( " geo " ,
std::make_pair ( 10.1 , 11.1 ),
100,
GeoUnit::KM,
10,
true,
std::back_inserter(mem_with_dist_hash));
// If the iterator is an iterator of a container of
// tuple<string, string, pair<double, double>, double>,
// we send the *GEORADIUS* command with *WITHHASH*, *WITHCOORD* and *WITHDIST* options.
std::vector<std::tuple<std::string, double , std::string>> mem_with_hash_coord_dist;
redis.georadius( " geo " ,
std::make_pair ( 10.1 , 11.1 ),
100,
GeoUnit::KM,
10,
true,
std::back_inserter(mem_with_hash_coord_dist));Consulte Redis.H para obter referências e exemplos da API no estilo doxygen e consulte os testes para outros exemplos.
Redis lança exceções se receber uma resposta de erro ou algo ruim acontece, por exemplo, não criou uma conexão com o servidor ou a conexão com o servidor está quebrada. Todas as exceções derivadas da classe Error . Consulte Errors.h para obter detalhes.
Error : erro genérico. É derivado de std::exception , e também é a classe base de outras exceções.IoError : Há algum erro de IO com a conexão.TimeoutError : Operação de leitura ou gravação foi cronometrada. É uma classe derivada de IoError .ClosedError : o servidor Redis fechou a conexão.ProtoError : o comando ou resposta é inválido e não podemos processá -lo com o protocolo Redis.OomError : a Biblioteca Hiredis recebeu um erro fora da memória.ReplyError : o servidor Redis retornou uma resposta de erro, por exemplo, tentamos chamar redis::lrange em um hash redis.WatchError : a chave assistida foi modificada. Consulte a seção de relógios para obter detalhes. Nota : A resposta nula não é tomada como uma exceção. Por exemplo, se tentarmos GET uma chave inexistente, obteremos uma resposta de string nula em massa . Em vez de lançar uma exceção, retornamos a resposta nula como um objeto NULL Optional<T> . Consulte também a seção opcional.
Normalmente, quando a exceção acontece, você não precisa criar um objeto Redis . É uma exceção segura e você pode reutilizar o objeto Redis . Mesmo que a conexão com o servidor Redis esteja quebrada e lança alguma exceção, digamos, IoError . Na próxima vez que você enviar comando com o objeto Redis , ele tentará se reconectar ao servidor Redis automaticamente. Esta regra também se aplica ao RedisCluster . No entanto, se Pipeline , Transcation e Subscriber lançam exceção, você precisa destruir o objeto e criar um novo. Veja a documentação correspondente para obter detalhes.
A seguir, é apresentado um exemplo de como capturar essas exceções:
try {
redis. set ( " key " , " value " );
// Wrong type error
redis. lpush ( " key " , { " a " , " b " , " c " });
} catch ( const ReplyError &err) {
// WRONGTYPE Operation against a key holding the wrong kind of value
cout << err. what () << endl;
} catch ( const TimeoutError &err) {
// reading or writing timeout
} catch ( const ClosedError &err) {
// the connection has been closed.
} catch ( const IoError &err) {
// there's an IO error on the connection.
} catch ( const Error &err) {
// other errors
} Existem muitos comandos Redis, não implementamos todos eles. No entanto, você pode usar os métodos genéricos Redis::command para enviar quaisquer comandos para Redis. Ao contrário de outras bibliotecas de clientes, Redis::command não usa o formato string para combinar argumentos de comando em uma string de comando. Em vez disso, você pode passar diretamente argumentos de comando do tipo StringView ou tipo aritmético como parâmetros de Redis::command . Pela razão pela qual não usamos o formato String, consulte esta discussão.
auto redis = Redis( " tcp://127.0.0.1 " );
// Redis class doesn't have built-in *CLIENT SETNAME* method.
// However, you can use Redis::command to send the command manually.
redis.command< void >( " client " , " setname " , " name " );
auto val = redis.command<OptionalString>( " client " , " getname " );
if (val) {
std::cout << *val << std::endl;
}
// NOTE: the following code is for example only. In fact, Redis has built-in
// methods for the following commands.
// Arguments of the command can be strings.
// NOTE: for SET command, the return value is NOT always void, I'll explain latter.
redis.command< void >( " set " , " key " , " 100 " );
// Arguments of the command can be a combination of strings and integers.
auto num = redis.command< long long >( " incrby " , " key " , 1 );
// Argument can also be double.
auto real = redis.command< double >( " incrbyfloat " , " key " , 2.3 );
// Even the key of the command can be of arithmetic type.
redis.command< void >( " set " , 100 , " value " );
val = redis.command<OptionalString>( " get " , 100 );
// If the command returns an array of elements.
std::vector<OptionalString> result;
redis.command( " mget " , " k1 " , " k2 " , " k3 " , std::back_inserter(result));
// Or just parse it into a vector.
result = redis.command<std::vector<OptionalString>>( " mget " , " k1 " , " k2 " , " k3 " );
// Arguments of the command can be a range of strings.
auto set_cmd_strs = { " set " , " key " , " value " };
redis.command< void >(set_cmd_strs.begin(), set_cmd_strs.end());
auto get_cmd_strs = { " get " , " key " };
val = redis.command<OptionalString>(get_cmd_strs.begin(), get_cmd_strs.end());
// If it returns an array of elements.
result.clear();
auto mget_cmd_strs = { " mget " , " key1 " , " key2 " };
redis.command(mget_cmd_strs.begin(), mget_cmd_strs.end(), std::back_inserter(result)); Nota : O nome de alguns comandos Redis é composto com duas strings, por exemplo, o SetName do cliente . Nesse caso, você precisa passar por essas duas cordas como dois argumentos para Redis::command .
// This is GOOD.
redis.command< void >( " client " , " setname " , " name " );
// This is BAD, and will fail to send command to Redis server.
// redis.command<void>("client setname", "name"); Como mencionei nos comentários, o comando SET nem sempre retorna void . Because if you try to set a (key, value) pair with NX or XX option, you might fail, and Redis will return a NULL REPLY . Besides the SET command, there're other commands whose return value is NOT a fixed type, you need to parse it by yourself. For example, Redis::set method rewrite the reply of SET command, and make it return bool type, ie if no NX or XX option specified, Redis server will always return an "OK" string, and Redis::set returns true ; if NX or XX specified, and Redis server returns a NULL REPLY , Redis::set returns false .
So Redis class also has other overloaded command methods, these methods return a ReplyUPtr , ie std::unique_ptr<redisReply, ReplyDeleter> , object. Normally you don't need to parse it manually. Instead, you only need to pass the reply to template <typename T> T reply::parse(redisReply &) to get a value of type T . Check the Return Type section for valid T types. If the command returns an array of elements, besides calling reply::parse to parse the reply to an STL container, you can also call template <typename Output> reply::to_array(redisReply &reply, Output output) to parse the result into an array or STL container with an output iterator.
Let's rewrite the above examples:
auto redis = Redis( " tcp://127.0.0.1 " );
redis.command( " client " , " setname " , " name " );
auto r = redis.command( " client " , " getname " );
assert (r);
// If the command returns a single element,
// use `reply::parse<T>(redisReply&)` to parse it.
auto val = reply::parse<OptionalString>(*r);
if (val) {
std::cout << *val << std::endl;
}
// Arguments of the command can be strings.
redis.command( " set " , " key " , " 100 " );
// Arguments of the command can be a combination of strings and integers.
r = redis.command( " incrby " , " key " , 1 );
auto num = reply::parse< long long >(*r);
// Argument can also be double.
r = redis.command( " incrbyfloat " , " key " , 2.3 );
auto real = reply::parse< double >(*r);
// Even the key of the command can be of arithmetic type.
redis.command( " set " , 100 , " value " );
r = redis.command( " get " , 100 );
val = reply::parse<OptionalString>(*r);
// If the command returns an array of elements.
r = redis.command( " mget " , " k1 " , " k2 " , " k3 " );
// Use `reply::to_array(redisReply&, OutputIterator)` to parse the result into an STL container.
std::vector<OptionalString> result;
reply::to_array (*r, std::back_inserter(result));
// Or just call `reply::parse` to parse it into vector.
result = reply::parse<std::vector<OptionalString>>(*r);
// Arguments of the command can be a range of strings.
auto get_cmd_strs = { " get " , " key " };
r = redis.command(get_cmd_strs.begin(), get_cmd_strs.end());
val = reply::parse<OptionalString>(*r);
// If it returns an array of elements.
result.clear();
auto mget_cmd_strs = { " mget " , " key1 " , " key2 " };
r = redis.command(mget_cmd_strs.begin(), mget_cmd_strs.end());
reply::to_array (*r, std::back_inserter(result)); In fact, there's one more Redis::command method:
template < typename Cmd, typename ...Args>
auto command (Cmd cmd, Args &&...args)
-> typename std::enable_if<!std::is_convertible<Cmd, StringView>::value, ReplyUPtr>::type;However, this method exposes some implementation details, and is only for internal use. You should NOT use this method.
You can use Redis::publish to publish messages to channels. Redis randomly picks a connection from the underlying connection pool, and publishes message with that connection. So you might publish two messages with two different connections.
When you subscribe to a channel with a connection, all messages published to the channel are sent back to that connection. So there's NO Redis::subscribe method. Instead, you can call Redis::subscriber to create a Subscriber and the Subscriber maintains a connection to Redis. The underlying connection is a new connection, NOT picked from the connection pool. This new connection has the same ConnectionOptions as the Redis object.
If you want to have different connection options, eg ConnectionOptions::socket_timeout , for different channels, you should create Redis objects with different connection options, then you can create Subscriber objects with these Redis objects. Check this issue for a use case.
ConnectionOptions opts1;
opts1.host = " 127.0.0.1 " ;
opts1.port = 6379 ;
opts1.socket_timeout = std::chrono::milliseconds( 100 );
auto redis1 = Redis(opts1);
// sub1's socket_timeout is 100ms.
auto sub1 = redis1.subscriber();
ConnectionOptions opts2;
opts2.host = " 127.0.0.1 " ;
opts2.port = 6379 ;
opts2.socket_timeout = std::chrono::milliseconds( 300 );
auto redis2 = Redis(opts2);
// sub2's socket_timeout is 300ms.
auto sub2 = redis2.subscriber(); NOTE : Although the above code creates two Redis objects, it has no performance penalty. Because Redis object creates connections lazily, ie no connection will be created until we send some command with Redis object, and the connection is created only when we call Redis::subscriber to create Subscriber object.
With Subscriber , you can call Subscriber::subscribe , Subscriber::unsubscribe , Subscriber::psubscribe and Subscriber::punsubscribe to send SUBSCRIBE , UNSUBSCRIBE , PSUBSCRIBE and PUNSUBSCRIBE commands to Redis.
Subscriber is NOT thread-safe. If you want to call its member functions in multi-thread environment, you need to synchronize between threads manually.
If any of the Subscriber 's method throws an exception other than ReplyError or TimeoutError , you CANNOT use it any more. Instead, you have to destroy the Subscriber object, and create a new one.
There are 6 kinds of messages:
We call messages of SUBSCRIBE , UNSUBSCRIBE , PSUBSCRIBE and PUNSUBSCRIBE types as META MESSAGE s.
In order to process these messages, you can set callback functions on Subscriber :
Subscriber::on_message(MsgCallback) : set callback function for messages of MESSAGE type, and the callback interface is: void (std::string channel, std::string msg) .Subscriber::on_pmessage(PatternMsgCallback) : set the callback function for messages of PMESSAGE type, and the callback interface is: void (std::string pattern, std::string channel, std::string msg) .Subscriber::on_meta(MetaCallback) : set callback function for messages of META MESSAGE type, and the callback interface is: void (Subscriber::MsgType type, OptionalString channel, long long num) . type is an enum, it can be one of the following enum: Subscriber::MsgType::SUBSCRIBE , Subscriber::MsgType::UNSUBSCRIBE , Subscriber::MsgType::PSUBSCRIBE , Subscriber::MsgType::PUNSUBSCRIBE , Subscriber::MsgType::MESSAGE , and Subscriber::MsgType::PMESSAGE . If you haven't subscribe/psubscribe to any channel/pattern, and try to unsubscribe/punsubscribe without any parameter, ie unsubscribe/punsubscribe all channels/patterns, channel will be null. So the second parameter of meta callback is of type OptionalString . All these callback interfaces pass std::string by value, and you can take their ownership (ie std::move ) safely.
You can call Subscriber::consume to consume messages published to channels/patterns that the Subscriber has been subscribed.
Subscriber::consume waits for message from the underlying connection. If the ConnectionOptions::socket_timeout is reached, and there's no message sent to this connection, Subscriber::consume throws a TimeoutError exception. If ConnectionOptions::socket_timeout is 0ms , Subscriber::consume blocks until it receives a message.
After receiving the message, Subscriber::consume calls the callback function to process the message based on message type. However, if you don't set callback for a specific kind of message, Subscriber::consume will consume the received message and discard it, ie Subscriber::consume returns without running the callback.
The following example is a common pattern for using Subscriber :
// Create a Subscriber.
auto sub = redis.subscriber();
// Set callback functions.
sub.on_message([](std::string channel, std::string msg) {
// Process message of MESSAGE type.
});
sub.on_pmessage([](std::string pattern, std::string channel, std::string msg) {
// Process message of PMESSAGE type.
});
sub.on_meta([](Subscriber::MsgType type, OptionalString channel, long long num) {
// Process message of META type.
});
// Subscribe to channels and patterns.
sub.subscribe( " channel1 " );
sub.subscribe({ " channel2 " , " channel3 " });
sub.psubscribe( " pattern1* " );
// Consume messages in a loop.
while ( true ) {
try {
sub. consume ();
} catch ( const Error &err) {
// Handle exceptions.
}
} If ConnectionOptions::socket_timeout is set, you might get TimeoutError exception before receiving a message:
while ( true ) {
try {
sub. consume ();
} catch ( const TimeoutError &e) {
// Try again.
continue ;
} catch ( const Error &err) {
// Handle other exceptions.
}
}The above examples use lambda as callback. If you're not familiar with lambda, you can also set a free function as callback. Check this issue for detail.
Pipeline is used to reduce RTT (Round Trip Time), and speed up Redis queries. redis-plus-plus supports pipeline with the Pipeline class.
You can create a pipeline with Redis::pipeline method, which returns a Pipeline object.
ConnectionOptions connection_options;
ConnectionPoolOptions pool_options;
Redis redis (connection_options, pool_options);
auto pipe = redis.pipeline(); When creating a Pipeline object, by default, Redis::pipeline method creates a new connection to Redis server. This connection is NOT picked from the connection pool, but a newly created connection. This connection has the same ConnectionOptions as other connections in the connection pool. Pipeline object maintains the new connection, and all piped commands are sent through this connection.
NOTE : By default, creating a Pipeline object is NOT cheap, since it creates a new connection. So you'd better reuse the Pipeline object as much as possible. Check this to see how to create a Pipeline object without creating a new connection.
You can send Redis commands through the Pipeline object. Just like the Redis class, Pipeline has one or more (overloaded) methods for each Redis command. However, you CANNOT get the replies until you call Pipeline::exec . So these methods do NOT return the reply, instead they return the Pipeline object itself. And you can chain these methods calls.
pipe.set( " key " , " val " ).incr( " num " ).rpush( " list " , { 0 , 1 , 2 }).command( " hset " , " key " , " field " , " value " ); Once you finish sending commands to Redis, you can call Pipeline::exec to get replies of these commands. You can also chain Pipeline::exec with other commands.
pipe.set( " key " , " val " ).incr( " num " );
auto replies = pipe.exec();
// The same as:
replies = pipe.set( " key " , " val " ).incr( " num " ).exec(); In fact, these commands won't be sent to Redis, until you call Pipeline::exec . So Pipeline::exec does 2 work in order: send all piped commands, then get all replies from Redis.
Also you can call Pipeline::discard to discard those piped commands.
pipe.set( " key " , " val " ).incr( " num " );
pipe.discard(); Pipeline::exec returns a QueuedReplies object, which contains replies of all commands that have been sent to Redis. You can use QueuedReplies::get method to get and parse the ith reply. It has 3 overloads:
template <typename Result> Result get(std::size_t idx) : Return the ith reply as a return value, and you need to specify the return type as tempalte parameter.template <typename Output> void get(std::size_t idx, Output output) : If the reply is of type Array Reply , you can call this method to write the ith reply to an output iterator. Normally, compiler will deduce the type of the output iterator, and you don't need to specify the type parameter explicitly.redisReply& get(std::size_t idx) : If the reply is NOT a fixed type, call this method to get a reference to redisReply object. In this case, you need to call template <typename T> T reply::parse(redisReply &) to parse the reply manually.Check the Return Type section for details on the return types of the result.
auto replies = pipe.set( " key " , " val " ).incr( " num " ).lrange( " list " , 0 , - 1 ).exec();
auto set_cmd_result = replies.get< bool >( 0 );
auto incr_cmd_result = replies.get< long long >( 1 );
std::vector<std::string> list_cmd_result;
replies.get( 2 , std::back_inserter(list_cmd_result)); If any of Pipeline 's method throws an exception other than ReplyError , the Pipeline object enters an invalid state. You CANNOT use it any more, but only destroy the object, and create a new one.
Pipeline is NOT thread-safe. If you want to call its member functions in multi-thread environment, you need to synchronize between threads manually.
YOU MUST CAREFULLY READ ALL WORDS IN THIS SECTION AND THE VERY IMPORTANT NOTES BEFORE USING THIS FEATURE!!!
In fact, you can also create a Pipeline object with a connection from the underlying connection pool, so that calling Redis::pipeline method can be much cheaper (since it doesn't need to create a new connection).
The prototype of Redis::pipeline is as follows: Pipeline pipeline(bool new_connection = true); . If new_connection is false, the Pipeline object will be created with a connection from the underlying pool.
ConnectionOptions connection_options;
ConnectionPoolOptions pool_options;
Redis redis (connection_options, pool_options);
// Create a Pipeline without creating a new connection.
auto pipe = redis.pipeline( false ); However, in this case, you MUST be very careful, otherwise, you might get bad performance or even dead lock. Because when you run command with Pipeline object, it will hold the connection until Pipeline::exec , Pipeline::discard or Pipeline 's destructor is called (the connection will also be released if any method of Pipeline throws Exception ). If the Pipeline object holds the connection for a long time, other Redis methods might not be able to get a connection from the underlying pool.
Check the following dead lock example:
// By defaul, create a `Redis` object with only ONE connection in pool.
// Also by default, the `ConnectionPoolOptions::wait_timeout` is 0ms,
// which means if the pool is empty, `Redis` method will be blocked until
// the pool is not empty.
Redis redis ( " tcp://127.0.0.1 " );
// Create a `Pipeline` with a connection in the underlying pool.
// In fact, the connection hasn't been fetched from the pool
// until some method of `Pipeline` has been called.
auto pipe = redis.pipeline( false );
// Now the `Pipeline` object fetches a connection from the pool.
pipe.set( " key1 " , " val " );
// `Pipeline` object still holds the connection until `Pipeline::exec`,
// `Pipeline::discard` or the destructor is called.
pipe.set( " key2 " , " val " );
// Try to send a command with `Redis` object.
// However, the pool is empty, since the `Pipeline` object still holds
// the connection, and this call will be blocked forever.
// DEAD LOCK!!!
redis.get( " key " );
// NEVER goes here.
pipe.exec();BEST PRACTICE :
When creating Pipeline without creating a new connection:
ConnectionPoolOptions::wait_timeout larger than 0ms (ie when pool is empty, never block forever).Pipeline 's methods.Pipeline methods and the Pipeline::exec in one statements.Pipeline related code in a block scope. ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
opts.socket_timeout = std::chrono::milliseconds( 50 );
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ;
// Always set `wait_timeout` larger than 0ms.
pool_opts.wait_timeout = std::chrono::milliseconds( 50 );
auto redis = Redis(opts, pool_opts);
{
// Better put `Pipeline` related code in a block scope.
auto pipe = redis. pipeline ( false );
pipe . set ( " key1 " , " val " );
// DON'T run slow operations here, since `Pipeline` object still holds
// the connection, other threads using this `Redis` object, might be blocked.
pipe . set ( " key2 " , " val " );
// When `Pipeline::exec` finishes, `Pipeline` releases the connection, and returns it to pool.
auto replies = pipe . exec ();
// This is even better, i.e. chain `Pipeline` methods with `Pipeline::exec`.
replies = pipe . set ( " key1 " , " val " ). set ( " key2 " , " val " ). exec ();
}
for ( auto i = 0 ; i < 10 ; ++i) {
// This operation, i.e. creating a `Pipeline` object with connection in pool, is cheap
auto pipe = redis. pipeline ( false );
// Fetch a connection from the underlying pool, and hold it.
pipe . set ( " key1 " , " val " ). set ( " key2 " , " val " );
// Although `Pipeline::exec` and `Pipeline::discard` haven't been called,
// when `Pipeline`'s destructor is called, the connection will also be
// returned to the pool.
}Transaction is used to make multiple commands runs atomically.
You can create a transaction with Redis::transaction method, which returns a Transaction object.
ConnectionOptions connection_options;
ConnectionPoolOptions pool_options;
Redis redis (connection_options, pool_options);
auto tx = redis.transaction(); As the Pipeline class, Transaction maintains a newly created connection to Redis. This connection has the same ConnectionOptions as the Redis object.
NOTE : Creating a Transaction object is NOT cheap, since it creates a new connection. So you'd better reuse the Transaction as much as possible. Check this to see how to create a Transaction object without creating a new connection.
Also you don't need to send MULTI command to Redis. Transaction will do that for you automatically.
Transaction shares most of implementation with Pipeline . It has the same interfaces as Pipeline . You can send commands as what you do with Pipeline object.
tx.set( " key " , " val " ).incr( " num " ).lpush( " list " , { 0 , 1 , 2 }).command( " hset " , " key " , " field " , " val " ); When you call Transaction::exec , you explicitly ask Redis to execute those queued commands, and return the replies. Otherwise, these commands won't be executed. Also, you can call Transaction::discard to discard the execution, ie no command will be executed. Both Transaction::exec and Transaction::discard can be chained with other commands.
auto replies = tx.set( " key " , " val " ).incr( " num " ).exec();
tx.set( " key " , " val " ).incr( " num " );
// Discard the transaction.
tx.discard();See Pipeline's Parse Replies section for how to parse the replies.
Normally, we always send multiple commnds in a transaction. In order to improve the performance, you can send these commands in a pipeline. You can create a piped transaction by passing true as parameter of Redis::transaction method.
// Create a piped transaction
auto tx = redis.transaction( true );With this piped transaction, all commands are sent to Redis in a pipeline.
If any of Transaction 's method throws an exception other than WatchError or ReplyError , the Transaction object enters an invalid state. You CANNOT use it any more, but only destroy the object and create a new one.
Transacation is NOT thread-safe. If you want to call its member functions in multi-thread environment, you need to synchronize between threads manually.
WATCH is used to provide a check-and-set(CAS) behavior to Redis transactions.
The WATCH command must be sent in the same connection as the transaction. And normally after the WATCH command, we also need to send some other commands to get data from Redis before executing the transaction. Take the following check-and-set case as an example:
WATCH key // watch a key
val = GET key // get value of the key
new_val = val + 1 // incr the value
MULTI // begin the transaction
SET key new_val // set value only if the value is NOT modified by others
EXEC // try to execute the transaction.
// if val has been modified, the transaction won't be executed.
However, with Transaction object, you CANNOT get the result of commands until the whole transaction has been finished. Instead, you need to create a Redis object from the Transaction object. The created Redis object shares the connection with Transaction object. With this created Redis object, you can send WATCH command and any other Redis commands to Redis server, and get the result immediately.
Let's see how to implement the above example with redis-plus-plus :
auto redis = Redis( " tcp://127.0.0.1 " );
// Create a transaction.
auto tx = redis.transaction();
// Create a Redis object from the Transaction object. Both objects share the same connection.
auto r = tx.redis();
// If the watched key has been modified by other clients, the transaction might fail.
// So we need to retry the transaction in a loop.
while ( true ) {
try {
// Watch a key.
r. watch ( " key " );
// Get the old value.
auto val = r. get ( " key " );
auto num = 0 ;
if (val) {
num = std::stoi (*val);
} // else use default value, i.e. 0.
// Incr value.
++num;
// Execute the transaction.
auto replies = tx. set ( " key " , std::to_string (num)). exec ();
// Transaction has been executed successfully. Check the result and break.
assert (replies. size () == 1 && replies. get < bool >( 0 ) == true );
break ;
} catch ( const WatchError &err) {
// Key has been modified by other clients, retry.
continue ;
} catch ( const Error &err) {
// Something bad happens, and the Transaction object is no longer valid.
throw ;
}
} NOTE : in the example above, we create Transaction object outside the while loop, in order to avoid creating new connection again and again.
NOTE : YOU MUST CAREFULLY READ ALL WORDS AND THE VERY IMPORTANT NOTES LINK IN THIS SECTION BEFORE USING THIS FEATURE!!!
In fact, you can also create a transaction object with a connection from the underlying connection pool, so that calling Redis::transaction method can be much cheaper (since it doesn't need to create a new connection).
The prototype of Redis::transaction is as follows: Transaction transaction(bool piped = false, bool new_connection = true); . If new_connection is false, the Transaction object will be created with a connection from the underlying pool.
ConnectionOptions connection_options;
ConnectionPoolOptions pool_options;
Redis redis (connection_options, pool_options);
// Create a Transaction without creating a new connection.
auto tx = redis.transaction( false , false );However, in this case, you MUST be very careful, otherwise, you might get bad performance or even dead lock. Please carefully check the similar pipeline's VERY IMPORTANT NOTES section, before you use it!
Besides those very important notes, there's another important note for Transaction :
Redis object created by Transaction::Redis , ie destroy it ASAP.Check the following example:
auto redis = Redis(opts, pool_opts);
// Create a `Transaction` object without creating a new connection.
auto tx = redis.Transaction( false , false );
// Create a `Redis`, and this `Redis` object shares the same connection with the `Transaction` object.
auto r = tx.redis();
// Other code here...
// Execute the transaction.
auto replies = tx.set( " key " , " val " ).exec();
// Although `Transaction::exec` has been called, the connection has not been returned to pool.
// Because the `Redis` object, i.e. `r`, still holds the connection.So the above watch example should be modified as follows:
auto redis = Redis(opts, pool_opts);
// If the watched key has been modified by other clients, the transaction might fail.
// So we need to retry the transaction in a loop.
while ( true ) {
try {
// Create a transaction without creating a new connection.
auto tx = redis. transaction ( false , false );
// Create a Redis object from the Transaction object. Both objects share the same connection.
auto r = tx. redis ();
// Watch a key.
r. watch ( " key " );
// Get the old value.
auto val = r. get ( " key " );
auto num = 0 ;
if (val) {
num = std::stoi (*val);
} // else use default value, i.e. 0.
// Incr value.
++num;
// Execute the transaction.
auto replies = tx. set ( " key " , std::to_string (num)). exec ();
// Transaction has been executed successfully. Check the result and break.
assert (replies. size () == 1 && replies. get < bool >( 0 ) == true );
break ;
} catch ( const WatchError &err) {
// Key has been modified by other clients, retry.
continue ;
} catch ( const Error &err) {
// Something bad happens, and the Transaction object is no longer valid.
throw ;
}
} NOTE : The difference is that we create the Transaction object in the while loop (it's cheap, since it doesn't need to create a new connection). When the Transaction object and the Redis object created by Transaction::redis have been destroyed, the connection will be return to pool.
redis-plus-plus supports Redis Cluster. You can use RedisCluster class to send commands to Redis Cluster. It has similar interfaces as Redis class.
By default, RedisCluster connects to all master nodes in the cluster. For each master node, it maintains a connection pool. If you want to read from slave nodes, you need to explicitly set an option (see below for reference).
You can initialize a RedisCluster instance with ConnectionOptions and ConnectionPoolOptions . You only need to set one master node's host & port in ConnectionOptions , and RedisCluster will get other nodes' info automatically (with the CLUSTER SLOTS command). For each master node, it creates a connection pool with the specified ConnectionPoolOptions . If ConnectionPoolOptions is not specified, RedisCluster maintains a single connection to every master node.
// Set a master node's host & port.
ConnectionOptions connection_options;
connection_options.host = " 127.0.0.1 " ; // Required.
connection_options.port = 7000 ; // Optional. The default port is 6379.
connection_options.password = " auth " ; // Optional. No password by default.
// Automatically get other nodes' info,
// and connect to every master node with a single connection.
RedisCluster cluster1 (connection_options);
ConnectionPoolOptions pool_options;
pool_options.size = 3 ;
// For each master node, maintains a connection pool of size 3.
RedisCluster cluster2 (connection_options, pool_options); You can also specify connection option with an URI. However, in this way, you can only use default ConnectionPoolOptions , ie pool of size 1, and CANNOT specify password.
// Specify a master node's host & port.
RedisCluster cluster3 ( " tcp://127.0.0.1:7000 " );
// Use default port, i.e. 6379.
RedisCluster cluster4 ( " tcp://127.0.0.1 " ); If you want to scale read by reading (possible stale) data from slave nodes, you can specifiy Role::SLAVE as the third parameter of RedisCluster 's constructor. In this case, redis-plus-plus will randomly pick a replica node for each master node of the cluster, and create a connection pool for the replica node.
RedisCluster cluster (connection_options, pool_options, Role::SLAVE);
auto val = cluster.get( " key " ); In this case, you can only send readonly commands to Redis Cluster. If you try to send a write command, eg set , hset , redis-plus-plus will throw an exception. Currently, redis-plus-plus doesn't handle this case, ie sending write command in Role::SLAVE mode, elegantly, and you might get some performance problem. So, NEVER send write command in Role::SLAVE mode. I'll fix this issue in the future.
NOTE : In Role::SLAVE mode, you don't need to manually send READONLY command to slave nodes. Instead, redis-plus-plus will send READONLY command to slave nodes automatically.
RedisCluster only works with tcp connection. It CANNOT connect to Unix Domain Socket. If you specify Unix Domain Socket in ConnectionOptions , it throws an exception.ConnectionOptions::db is ignored. As we mentioned above, RedisCluster 's interfaces are similar to Redis . It supports most of Redis ' interfaces, including the generic command interface (see Redis ' API Reference section for details), except the following:
PING , INFO . Since there's no key parameter, RedisCluster has no idea on to which node these commands should be sent. However there're 2 workarounds for this problem:
Redis object with that node's host and port, and use the Redis object to do the work.Redis RedisCluster::redis(const StringView &hash_tag) to create a Redis object with a hash-tag specifying the node. In this case, the returned Redis object creates a new connection to Redis server. NOTE : the returned Redis object, IS NOT THREAD SAFE! . Also, when using the returned Redis object, if it throws exception, you need to destroy it, and create a new one with the RedisCluster::redis method.Also you can use the hash tags to send multiple-key commands.
See the example section for details.
You can publish and subscribe messages with RedisCluster . The interfaces are exactly the same as Redis , ie use RedisCluster::publish to publish messages, and use RedisCluster::subscriber to create a subscriber to consume messages. See Publish/Subscribe section for details.
You can also create Pipeline and Transaction objects with RedisCluster , but the interfaces are different from Redis . Since all commands in the pipeline and transaction should be sent to a single node in a single connection, we need to tell RedisCluster with which node the pipeline or transaction should be created.
Instead of specifying the node's IP and port, RedisCluster 's pipeline and transaction interfaces allow you to specify the node with a hash tag . RedisCluster will calculate the slot number with the given hash tag , and create a pipeline or transaction with the node holding the slot.
Pipeline RedisCluster::pipeline ( const StringView &hash_tag, bool new_connection = true );
Transaction RedisCluster::transaction ( const StringView &hash_tag, bool piped = false , bool new_connection = true ); With the created Pipeline or Transaction object, you can send commands with keys located on the same node as the given hash_tag . See Examples section for an example.
NOTE : By default, Pipeline and Transaction will be created with a new connection. In order to avoid creating new connection, you can pass false as the last parameter. However, in this case, you MUST be very careful, otherwise, you might get bad performance or even dead lock. Please carefully check the related pipeline section before using this feature.
# include < sw/redis++/redis++.h >
using namespace sw ::redis ;
auto redis_cluster = RedisCluster( " tcp://127.0.0.1:7000 " );
redis_cluster.set( " key " , " value " );
auto val = redis_cluster.get( " key " );
if (val) {
std::cout << *val << std::endl;
}
// With hash-tag.
redis_cluster.set( " key{tag}1 " , " val1 " );
redis_cluster.set( " key{tag}2 " , " val2 " );
redis_cluster.set( " key{tag}3 " , " val3 " );
std::vector<OptionalString> hash_tag_res;
redis_cluster.mget({ " key{tag}1 " , " key{tag}2 " , " key{tag}3 " },
std::back_inserter (hash_tag_res));
redis_cluster.lpush( " list " , { " 1 " , " 2 " , " 3 " });
std::vector<std::string> list;
redis_cluster.lrange( " list " , 0 , - 1 , std::back_inserter(list));
// Pipeline.
auto pipe = redis_cluster.pipeline( " counter " );
auto replies = pipe.incr( " {counter}:1 " ).incr( " {counter}:2 " ).exec();
// Transaction.
auto tx = redis_cluster.transaction( " key " );
replies = tx.incr( " key " ).get( " key " ).exec();
// Create a Redis object with hash-tag.
// It connects to the Redis instance that holds the given key, i.e. hash-tag.
auto r = redis_cluster.redis( " hash-tag " );
// And send command without key parameter to the server.
r.command( " client " , " setname " , " connection-name " ); NOTE : By default, when you use RedisCluster::redis(const StringView &hash_tag, bool new_connection = true) to create a Redis object, instead of picking a connection from the underlying connection pool, it creates a new connection to the corresponding Redis server. So this is NOT a cheap operation, and you should try to reuse this newly created Redis object as much as possible. If you pass false as the second parameter, you can create a Redis object without creating a new connection. However, in this case, you should be very careful, otherwise, you might get bad performance or even dead lock. Please carefully check the related pipeline section before using this feature.
// This is BAD! It's very inefficient.
// NEVER DO IT!!!
// After sending PING command, the newly created Redis object will be destroied.
cluster.redis( " key " ).ping();
// Then it creates a connection to Redis, and closes the connection after sending the command.
cluster.redis( " key " ).command( " client " , " setname " , " hello " );
// Instead you should reuse the Redis object.
// This is GOOD!
auto redis = cluster.redis( " key " );
redis.ping();
redis.command( " client " , " setname " , " hello " );
// This is GOOD! Create `Redis` object without creating a new connection. Use it, and destroy it ASAP.
cluster.redis( " key " , false ).ping(); RedisCluster maintains the newest slot-node mapping, and sends command directly to the right node. Normally it works as fast as Redis . If the cluster reshards, RedisCluster will follow the redirection, and it will finally update the slot-node mapping. It can correctly handle the following resharding cases:
redis-plus-plus is able to handle both MOVED and ASK redirections, so it's a complete Redis Cluster client.
If master is down, the cluster will promote one of its replicas to be the new master. redis-plus-plus can also handle this case:
Since redis-plus-plus 1.3.13, it also updates the slot-node mapping every ClusterOptions::slot_map_refresh_interval time interval (by default, it updates every 10 seconds).
Redis Sentinel provides high availability for Redis. If Redis master is down, Redis Sentinels will elect a new master from slaves, ie failover. Besides, Redis Sentinel can also act like a configuration provider for clients, and clients can query master or slave address from Redis Sentinel. So that if a failover occurs, clients can ask the new master address from Redis Sentinel.
redis-plus-plus supports getting Redis master or slave's IP and port from Redis Sentinel. In order to use this feature, you only need to initialize Redis object with Redis Sentinel info, which is composed with 3 parts: std::shared_ptr<Sentinel> , master name and role (master or slave).
Before using Redis Sentinel with redis-plus-plus , ensure that you have read Redis Sentinel's doc.
You can create a std::shared_ptr<Sentinel> object with SentinelOptions .
SentinelOptions sentinel_opts;
sentinel_opts.nodes = {{ " 127.0.0.1 " , 9000 },
{ " 127.0.0.1 " , 9001 },
{ " 127.0.0.1 " , 9002 }}; // Required. List of Redis Sentinel nodes.
// Optional. Timeout before we successfully connect to Redis Sentinel.
// By default, the timeout is 100ms.
sentinel_opts.connect_timeout = std::chrono::milliseconds( 200 );
// Optional. Timeout before we successfully send request to or receive response from Redis Sentinel.
// By default, the timeout is 100ms.
sentinel_opts.socket_timeout = std::chrono::milliseconds( 200 );
auto sentinel = std::make_shared<Sentinel>(sentinel_opts); SentinelOptions::connect_timeout and SentinelOptions::socket_timeout CANNOT be 0ms, ie no timeout and block forever. Otherwise, redis-plus-plus will throw an exception.
See SentinelOptions for more options.
Besides std::shared_ptr<Sentinel> and master name, you also need to specify a role. There are two roles: Role::MASTER , and Role::SLAVE .
With Role::MASTER , redis-plus-plus will always connect to current master instance, even if a failover occurs. Each time when redis-plus-plus needs to create a new connection to master, or a connection is broken, and it needs to reconnect to master, redis-plus-plus will ask master address from Redis Sentinel, and connects to current master. If a failover occurs, redis-plus-plus can automatically get the address of the new master, and refresh all connections in the underlying connection pool.
Similarly, with Role::SLAVE , redis-plus-plus will always connect to a slave instance. A master might have several slaves, redis-plus-plus will randomly pick one, and connect to it, ie all connections in the underlying connection pool, connect to the same slave instance (check this discussion on why redis-plus-plus not connect to all slaves). If the connection is broken, while this slave instance is still an alive slave, redis-plus-plus will reconnect to this slave. However, if this slave instance is down, or it has been promoted to be the master, redis-plus-plus will randomly connect to another slave. If there's no slave alive, it throws an exception.
When creating a Redis object with sentinel, besides the sentinel info, you should also provide ConnectionOptions and ConnectionPoolOptions . These two options are used to connect to Redis instance. ConnectionPoolOptions is optional, if not specified, it creates a single connection the instance.
ConnectionOptions connection_opts;
connection_opts.password = " auth " ; // Optional. No password by default.
connection_opts.connect_timeout = std::chrono::milliseconds( 100 ); // Required.
connection_opts.socket_timeout = std::chrono::milliseconds( 100 ); // Required.
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ; // Optional. The default size is 1.
auto redis = Redis(sentinel, " master_name " , Role::MASTER, connection_opts, pool_opts); You might have noticed that we didn't specify the host and port fields for ConnectionOptions . Because, Redis will get these info from Redis Sentinel. Also, in this case, ConnectionOptions::connect_timeout and ConnectionOptions::socket_timeout CANNOT be 0ms, otherwise, it throws an exception. So you always need to specify these two timeouts manually.
After creating the Redis object with sentinel, you can send commands with it, just like an ordinary Redis object.
If you want to write to master, and scale read with slaves. You can use the following pattern:
auto sentinel = std::make_shared<Sentinel>(sentinel_opts);
auto master = Redis(sentinel, " master_name " , Role::MASTER, connection_opts, pool_opts);
auto slave = Redis(sentinel, " master_name " , Role::SLAVE, connection_opts, pool_opts);
// Write to master.
master.set( " key " , " value " );
// Read from slave.
slave.get( " key " );Since Redis 5.0, it introduces a new data type: Redis Stream . redis-plus-plus has built-in methods for all stream commands except the XINFO command (of course, you can use the Generic Command Interface to send XINFO command).
However, the replies of some streams commands, ie XPENDING , XREAD , are complex. So I'll give some examples to show you how to work with these built-in methods.
auto redis = Redis( " tcp://127.0.0.1 " );
using Attrs = std::vector<std::pair<std::string, std::string>>;
// You can also use std::unordered_map, if you don't care the order of attributes:
// using Attrs = std::unordered_map<std::string, std::string>;
Attrs attrs = { { " f1 " , " v1 " }, { " f2 " , " v2 " } };
// Add an item into the stream. This method returns the auto generated id.
auto id = redis.xadd( " key " , " * " , attrs.begin(), attrs.end());
// Each item is assigned with an id: pair<id, Optional<attributes>>.
// NOTE: the attribute part might be nil reply, check [this issue](https://github.com/sewenew/redis-plus-plus/issues/283) for detail.
using Item = std::pair<std::string, Optional<Attrs>>;
using ItemStream = std::vector<Item>;
// If you don't care the order of items in the stream, you can also use unordered_map:
// using ItemStream = std::unordered_map<std::string, Attrs>;
// Read items from a stream, and return at most 10 items.
// You need to specify a key and an id (timestamp + offset).
std::unordered_map<std::string, ItemStream> result;
redis.xread( " key " , id, 10 , std::inserter(result, result.end()));
// Read from multiple streams. For each stream, you need to specify a key and an id.
std::unordered_map<std::string, std::string> keys = { { " key " , id}, { " another-key " , " 0-0 " } };
redis.xread(keys.begin(), keys.end(), 10 , std::inserter(result, result.end()));
// Block for at most 1 second if currently there's no data in the stream.
redis.xread( " key " , id, std::chrono::seconds( 1 ), 10 , std::inserter(result, result.end()));
// Block for multiple streams.
redis.xread(keys.begin(), keys.end(), std::chrono::seconds( 1 ), 10 , std::inserter(result, result.end()));
// Read items in a range:
ItemStream item_stream;
redis.xrange( " key " , " - " , " + " , std::back_inserter(item_stream));
// Trim the stream to a given number of items. After the operation, the stream length is NOT exactly
// 10. Instead, it might be much larger than 10.
// `XTRIM key MAXLEN 10`
redis.xtrim( " key " , 10 );
// In order to trim the stream to exactly 10 items, specify the third argument, i.e. approx, as false.
// `XTRIM key MAXLEN ~ 10`
redis.xtrim( " key " , 10 , false );
// Delete an item from the stream.
redis.xdel( " key " , id);
// Create a consumer group.
redis.xgroup_create( " key " , " group " , " $ " );
// If the stream doesn't exist, you can set the fourth argument, i.e. MKSTREAM, to be true.
// redis.xgroup_create("key", "group", "$", true);
id = redis.xadd( " key " , " * " , attrs.begin(), attrs.end());
// Read item by a consumer of a consumer group.
redis.xreadgroup( " group " , " consumer " , " key " , " > " , 1 , std::inserter(result, result.end()));
using PendingItem = std::tuple<std::string, std::string, long long , long long >;
std::vector<PendingItem> pending_items;
// Get pending items of a speicified consumer.
redis.xpending( " key " , " group " , " - " , " + " , 1 , " consumer " , std::back_inserter(pending_items));
redis.xack( " key " , " group " , id);
redis.xgroup_delconsumer( " key " , " group " , " consumer " );
redis.xgroup_destroy( " key " , " group " );If you have any problem on sending stream commands to Redis, please feel free to let me know.
Redis Modules enrich Redis. However, redis-plus-plus does not have built-in support/method for these modules, although you can use the generic interface to send commands related to these modules.
The generic command interface uses the second argument as the key for hashing. If your custom command places the key at a different argument (ie: module-name create key1 arg1 arg2 ), and you are using the RedisCluster client, then it will fail to send the command to the correct Redis instance. In this case you could use the following work-around:
auto redis_cluster = RedisCluster( " tcp://127.0.0.1:6379 " );
std::vector<std::string> raw_cmd;
raw_cmd.push_back( " module-name " );
raw_cmd.push_back( " create " );
raw_cmd.push_back( " key1 " );
raw_cmd.push_back( " arg1 " );
raw_cmd.push_back( " arg2 " );
// create it with a connection from the underlying connection pool
auto redis = redis_cluster.redis( " key1 " , false );
redis.command< void >(raw_cmd.begin(), raw_cmd.end());Fortunately, @wingunder did a great job to make the work easier. He wrote redis-plus-plus-modules, which is a header only project that has built-in support for some popular modules. If you need to work with Redis Modules, you should have a try.
@wingunder also contributes a lot to redis-plus-plus . Many thanks to @wingunder!
redis-plus-plus also supports async interface, however, async support for Transaction is still on the way.
The async interface depends on third-party event library, and so far, only libuv is supported.
You must install libuv (eg apt-get install libuv1-dev ) before install hiredis and redis-plus-plus . The required libuv version is 1.x .
hiredis v1.0.0's async interface is different from older version, and redis-plus-plus only supports hiredis v1.0.0 or later. So you need to ensure you've installed the right version of hiredis before installing redis-plus-plus . Also, you should NEVER install multiple versions of hiredis , otherwise, you'll get some wired problems. If you already installed an older version, remove it, and install a newer version.
When installing redis-plus-plus , you should specify the following command line option: -DREDIS_PLUS_PLUS_BUILD_ASYNC=libuv .
cmake -DCMAKE_PREFIX_PATH=/installation/path/to/libuv/and/hiredis -DREDIS_PLUS_PLUS_BUILD_ASYNC=libuv ..
make
make install The async interface is similar to sync interface, except that you should include sw/redis++/async_redis++.h , and define an object of sw::redis::AsyncRedis , and the related methods return Future object (so far, only std::future and boost::future are supported, support for other implementations of future is on the way).
However, C++'s support for continuation and executor is not done yet, so the async interface also supports the old callback way. The following is the callback interface:
template <typename ReplyType>
void (sw::redis::Future<ReplyType> &&fut);
In the callback, in order to get the reply, you need to call sw::redis::Future<ReplyType>::get() . If something bad happened, get throws exception. So you need to catch possible exception in the callback. The callback runs in the underlying event loop thread, so DO NOT do slow operations in the callback, otherwise, it blocks the event loop and hurts performance.
OBSERVAÇÃO :
AsyncRedis alive before all callbacks have been executed (with some synchronization work). Because, once AsyncRedis is destroyed, it will stop the underlying event loop. And any commands that haven't sent to Redis yet, might fail. These notes also work with AsyncRedisCluster .
# include < sw/redis++/async_redis++.h >
ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ;
auto async_redis = AsyncRedis(opts, pool_opts);
Future<string> ping_res = async_redis.ping();
// Async interface returning Future object.
Future< bool > set_res = async_redis.set( " key " , " val " );
// Async interface with callback.
async_redis.set( " key " , " val " ,
[](Future< bool > &&fut) {
try {
auto set_res = fut. get ();
} catch ( const Error &err) {
// handle error
}
});
Future<Optional<string>> get_res = async_redis.get( " key " );
async_redis.get( " key " , [](Future<OptionalString> &&fut) {
try {
auto val = fut. get ();
if (val)
cout << *val << endl;
else
cout << " not exist " << endl;
} catch ( const Error &err) {
// handle error
}
});
unordered_map<string, string> m = {{ " a " , " b " }, { " c " , " d " }};
Future< void > hmset_res = async_redis.hmset( " hash " , m.begin(), m.end());
auto hgetall_res = async_redis.hgetall<std::unordered_map<std::string, std::string>>( " hash " );
cout << ping_res.get() << endl;
cout << set_res.get() << endl;
auto val = get_res.get();
if (val)
cout << *val << endl;
else
cout << " not exist " << endl;
hmset_res.get();
for ( const auto &ele : hgetall_res.get())
cout << ele.first << " t " << ele.second << endl;
// Generic interface.
// There's no *AsyncRedis::client_getname* interface.
// But you can use *Redis::command* to get the client name.
auto getname_res = async_redis.command<OptionalString>( " client " , " getname " );
val = getname_res.get();
if (val) {
std::cout << *val << std::endl;
}
async_redis.command<OptionalString>( " client " , " getname " ,
[](Future<OptionalString> &&fut) {
try {
auto val = fut. get ();
} catch ( const Error &e) {
// handle error
}
});
async_redis.command< long long >( " incr " , " number " ,
[](Future< long long > &&fut) {
try {
cout << fut. get () << endl;
} catch ( const Error &e) {
// handle error
}
});Aysnc interface also supports Redis Sentinel.
# include < sw/redis++/async_redis++.h >
SentinelOptions sentinel_opts;
sentinel_opts.nodes = {
{ " 127.0.0.1 " , 8000 },
{ " 127.0.0.1 " , 8001 },
{ " 127.0.0.1 " , 8002 }
};
sentinel_opts.connect_timeout = std::chrono::milliseconds( 100 );
sentinel_opts.socket_timeout = std::chrono::milliseconds( 100 );
auto sentinel = std::make_shared<AsyncSentinel>(sentinel_opts);
onnectionOptions connection_opts;
connection_opts.connect_timeout = std::chrono::milliseconds( 100 ); // Required.
connection_opts.socket_timeout = std::chrono::milliseconds( 100 ); // Required.
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ; // Optional. The default size is 1.
// Connect to master node.
AsyncRedis redis (sentinel, " mymaster " , Role::MASTER, connection_opts, pool_opts);
// The following code randomly connects to one of the slave nodes.
// AsyncRedis redis(sentinel, "mymaster", Role::SLAVE, connection_opts, pool_opts);
redis.set( " key " , " value " );
auto value = redis.get( " key " ).get(); The async support for sentinel is similar with the sync one, except that you need to create an AsyncSentinel object instead of a Sentinel object. Check Redis Sentinel for more details on SentinelOptions , ConnectionOptions and Role .
Aysnc interface also supports Redis Cluster. Instead of AsyncRedis , you need to create an AsyncRedisCluster object.
ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ;
auto async_cluster = AsyncRedisCluster(opts, pool_opts);
Future< bool > set_res = async_cluster.set( " key " , " val " );
Future<Optional<string>> get_res = async_cluster.get( " key " );
auto mget_res = async_cluster.mget<std::vector<OptionalString>>({ " {hashtag}key1 " , " {hashhag}key2 " , " {hashtag}key3 " });
unordered_map<string, string> m = {{ " a " , " b " }, { " c " , " d " }};
Future< void > hmset_res = async_redis.hmset( " hash " , m.begin(), m.end());
// Create an AsyncRedis object with hash-tag, so that we can send commands that has no key.
// It connects to Redis instance that holds the given key, i.e. hash-tag.
auto r = async_cluster.redis( " hash-tag " );
Future<string> ping_res = r.command<string>( " ping " ); NOTE : By default, when you use AsyncRedisCluster::redis(const StringView &hash_tag, bool new_connection = true) to create an AsyncRedis object, instead of picking a connection from the underlying connection pool, it creates a new connection to the corresponding Redis server. So this is NOT a cheap operation, and you should try to reuse this newly created AsyncRedis object as much as possible. If you pass false as the second parameter, you can create a AsyncRedis object without creating a new connection. However, in this case, you should be very careful, otherwise, you might get bad performance or even dead lock. Please carefully check the related pipeline section before using this feature. Also the returned AsyncRedis object is NOT thread-safe, and if it throws exception, you need to destroy it, and create a new one with the AsyncRedisCluster::redis method.
NOTE : I'm not quite satisfied with the interface of AsyncSubscriber . If you have a better idea, feel free to open an issue for discussion.
You can use AsyncSubscriber to subscribe to channels or patterns asynchronously. The interface is similar to Subscriber , except a few differences (please read Publish/Subscribe section first):
consume method for AsyncSubscriber . Once you setup callbacks, and subscribe to some channel, redis-plus-plus will run callbacks with received messages in the underlying event loop.AsyncSubscriber::subscribe , AsyncSubscriber::psubscriber and other related methods return Future<void> . You can use it to check if the subscription has been sent.AsyncSubscriber::on_error(ErrCallback &&) to handle possible errors. The error callback interface is: void (std::exception_ptr err) , and you can get the exception with given exception pointer. AsyncSubscriber is NOT thread-safe. If you want to call its member functions in multi-thread environment, you need to synchronize between threads manually.AsyncSubscriber is destroyed, the underlying connection will be closed. If there're still channels or patterns not unsubscribed, the error callback will be called. In order to avoid it, you need to call AsyncSubscriber::unsubscribe() or AsyncSubscriber::punsubscribe() to unsubscribe all channels or patterns before destroying AsyncSubscriber . NOTE: this behavior might be changed in the future, ie we'll unsubscribe channels and patterns in the destructor of AsyncSubscriber . The following example is a common pattern to use AsyncSubscriber :
// Create an `AsyncSubscriber`. You can create it with either an `AsyncRedis` or `AsyncRedisCluster` object.
auto sub = async_redis.subscriber();
// Set callbacks.
sub.on_message([](std::string channel, std::string msg) {
// Process message of MESSAGE type.
});
sub.on_pmessage([](std::string pattern, std::string channel, std::string msg) {
// Process message of PMESSAGE type.
});
sub.on_meta([](Subscriber::MsgType type, OptionalString channel, long long num) {
// Process message of META type.
});
// You need to set error callback to handle error.
sub.on_error([](std::exception_ptr e) {
try {
std::rethrow_exception (e);
} catch ( const std:: exception &err) {
std::cerr << " err: " << err. what () << std::endl;
}
});
// Subscribe to channels and patterns.
Future< void > fut1 = sub.subscribe( " channel " );
Future< void > fut2 = sub.psubscribe( " pattern1* " );
// Once you call `subscribe` or `psubscribe`, callbacks will be run in the underlying
// event loop automatically. NOTE : The following is an experimental feature, and might be modified or abandaned in the future.
By default, AsyncRedis and AsyncRedisCluster create a default event loop, and runs the loop in a dedicated thread to handle read and write operations. However, you can also share the underlying event loop with multiple AsyncRedis and AsyncRedisCluster objects. In order to do that, you need to create a std::shared_ptr<EventLoop> , and pass it to the constructors of AsyncRedis and AsyncRedisCluster .
auto event_loop = std::make_shared<EventLoop>();
auto redis = AsyncRedis(connection_opts, pool_opts, loop);
auto cluster = AsyncRedisCluster(connection_opts, pool_opts, Role::MASTER, loop); NOTE : You must ensure event_loop lives longer than AsyncRedis and AsyncRedisCluster objects.
Unfortunately, std::future doesn't support continuation so far, which is inconvenient. However, some other libraries, eg boost and folly, have continuation support.
By default, redis-plus-plus returns std::future for async interface. However, you can also make it return boost::future by specifying -DREDIS_PLUS_PLUS_ASYNC_FUTURE=boost when running cmake ( folly and other libraries might be supported in the future). Of course, in this case, you need to install Boost first (the minimum version requirement for Boost is 1.55.0 ).
cmake -DREDIS_PLUS_PLUS_BUILD_ASYNC=libuv -DREDIS_PLUS_PLUS_ASYNC_FUTURE=boost ..NOTE : When building your application code, don't forget to link boost related libs, eg -lboost_thread, -lboost_system.
Then you can take advantage of boost::future 's continuation support:
# include < sw/redis++/async_redis++.h >
ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
auto redis = AsyncRedis(opts);
auto fut = redis.get( " key " ).then([](sw::redis::Future<sw::redis::Optional<std::string>> fut) {
auto val = fut. get ();
if (val) cout << *val << endl;
});
// Do other things
// Wait for the continuation finishes.
fut.get();You can also use a thread pool to run the continuation:
# define BOOST_THREAD_PROVIDES_EXECUTORS
// You might also need to `#define BOOST_THREAD_USES_MOVE` with some version of Boost.
// See [this issue](https://github.com/sewenew/redis-plus-plus/issues/272) for detail.
# include < sw/redis++/async_redis++.h >
# include < boost/thread/executors/basic_thread_pool.hpp >
boost::executors::basic_thread_pool pool ( 3 );
auto fut = redis.get( " key " ).then(pool,
[](sw::redis::Future<sw::redis::Optional<std::string>> fut) {
auto val = fut. get ();
if (val) cout << *val << endl;
});
// Do other things
fut.get();redis-plus-plus also supports coroutine interface, however, coroutine support for Subscriber and Transaction is still on the way.
NOTE : Coroutine support is still experimental, and the interface might be changed in the future.
The coroutine interface depends on async interface, which depends on third-party event library. So you need to install libuv first, and hiredis v1.0.0 or later. Check async interface for detail.
When installing redis-plus-plus , you should specify the following command line options: -DREDIS_PLUS_PLUS_BUILD_ASYNC=libuv , -DREDIS_PLUS_PLUS_BUILD_CORO=ON and -DREDIS_PLUS_PLUS_CXX_STANDARD=20 .
cmake -DCMAKE_PREFIX_PATH=/installation/path/to/libuv/and/hiredis -DREDIS_PLUS_PLUS_CXX_STANDARD=20 -DREDIS_PLUS_PLUS_BUILD_ASYNC=libuv -DREDIS_PLUS_PLUS_BUILD_CORO=ON ..
make
make install The coroutine interface is similar to sync interface, except that you should include sw/redis++/co_redis++.h , and define an object of sw::redis::CoRedis or sw::redis::CoRedisCluster , and the related methods return sw::redis::CoRedis::Awaiter<Result> or sw::redis::CoRedisCluster::Awaiter<Result> object.
OBSERVAÇÃO :
# include < sw/redis++/co_redis++.h >
# include < cppcoro/task.hpp >
# include < cppcoro/sync_wait.hpp >
ConnectionOptions opts;
opts.host = " 127.0.0.1 " ;
opts.port = 6379 ;
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ;
// `CoRedisCluster` has similar inteface as `CoRedis`.
// auto co_redis_cluster = CoRedisCluster(opts, pool_opts);
auto co_redis = CoRedis(opts, pool_opts);
cppcoro::sync_wait ([&co_redis]() -> cppcoro::task<> {
try {
co_await co_redis. set ( " key " , " val " );
auto val = co_await co_redis. get ( " key " );
if (val)
cout << *val << endl;
else
cout << " not exist " << endl;
co_await co_redis. command < long long >( " incr " , " num " );
val = co_await co_redis. command <OptionalString>( " get " , " num " );
} catch ( const Error &e) {
cout << e. what () << endl;
}
}());Coroutine interface also supports Redis Sentinel.
# include < sw/redis++/co_redis++.h >
SentinelOptions sentinel_opts;
sentinel_opts.nodes = {
{ " 127.0.0.1 " , 8000 },
{ " 127.0.0.1 " , 8001 },
{ " 127.0.0.1 " , 8002 }
};
sentinel_opts.connect_timeout = std::chrono::milliseconds( 100 );
sentinel_opts.socket_timeout = std::chrono::milliseconds( 100 );
auto sentinel = std::make_shared<CoSentinel>(sentinel_opts);
onnectionOptions connection_opts;
connection_opts.connect_timeout = std::chrono::milliseconds( 100 ); // Required.
connection_opts.socket_timeout = std::chrono::milliseconds( 100 ); // Required.
ConnectionPoolOptions pool_opts;
pool_opts.size = 3 ; // Optional. The default size is 1.
// Connect to master node.
CoRedis co_redis (sentinel, " mymaster " , Role::MASTER, connection_opts, pool_opts);
// The following code randomly connects to one of the slave nodes.
// CoRedis co_redis(sentinel, "mymaster", Role::SLAVE, connection_opts, pool_opts);
cppcoro::sync_wait ([&co_redis]() -> cppcoro::task<> {
try {
auto val = co_await co_redis. get ( " key " );
if (val)
cout << *val << endl;
else
cout << " not exist " << endl;
} catch ( const Error &e) {
cout << e. what () << endl;
}
}()); The coroutine support for sentinel is similar with the sync one, except that you need to create an CoSentinel object instead of a Sentinel object. Check Redis Sentinel for more details on SentinelOptions , ConnectionOptions and Role .
We can create many interesting data structures and algorithms based on Redis, such as Redlock. We call these data structures and algorithms as Redis Patterns . redis-plus-plus will support some of these patterns.
NOTE : These patterns will be first implemented on the patterns branch. I'd like to hear your feedback on the API of these patterns, and when these APIs become stable, I'll merge the code into the master branch. So APIs on the patterns branch are NOT stable, and might be changed in the future.
Redlock is a distributed lock based on Redis. Thanks to @wingunder's suggestion, redis-plus-plus supports Redlock now. @wingunder and I made two different implementation of Redlock: one based on Lua script, and the other based on transaction. The Lua script version should be faster, and also it has many other parameters to control the behavior. However, if you are not allowed to, or don't want to run Lua scripts inside Redis, you could try using the transaction version.
Also there's a high level API, which works like std::mutex . With this high level API, you don't need to manually extend the lock, instead, the lock will be automatically extened by redis-plus-plus.
The basic idea of acquiring a Redlock is setting a key in Redis if the key does not exist. Since Redis operation is atomic, when mutiple clients acquire the same lock, ie setting the same key if it does not exist, only one client wins, and others will find the key has already been set. So only one client can acquire the lock, and others have to wait and try again.
When setting the key, we also need to set a TTL/expireation for the key. Otherwise, if the winning client crashes, the lock cannot be acquired by others forever. However, it also brings a new problem. Since the key has a TTL, once you acquire the lock, you must ensure all code in critical section must be finished before the key expires. Otherwise, other clients might acquire the lock successfully when you are still running critical section code (ie more than one clients acquire the lock successfully). So when you run critical section code, you have to check if the key is going to be expired and extend the lock (ie extending the TTL) before key expires, from time to time.
Also, in order to make the algorithm more robust, normally we need to set key on multiple independent stand-alone Redis (not Redis Cluster).
There're still more details on the mechanism of Redlock. Please read Redlock's doc for more info, before using it.
The high level API is quite simple. It works like a std::mutex , and can be used with std::lock_guard and std::unique_lock . Also it can automatically extend the lock before the key expires. So that user code doesn't need to extend the lock manually. In order to use Redlock, you can create a RedMutex object with the following parameters:
Redis instances: There're two versions of Redlock, ie single instance version and multiple instances version. The multiple instances version is more robust.RedMutex should be created with the same resource id.RedMutexOptions (optional): Some options to control the behavior of RedMutex . If not specified, default options will be used. Check below for more detail.LockWatcher (optional): A watcher which will automatically extend the lock before it expires. So that you don't need to manually check if the lock has been expired. If no watcher is specified (the default behavior), redis-plus-plus will create a one for this Redlock. Check below for more detail. class RedMutex {
public:
RedMutex(std::initializer_list<std::shared_ptr<Redis>> masters,
const std::string &resource,
std::function<void (std::exception_ptr)> auto_extend_err_callback = nullptr,
const RedMutexOptions &opts = {},
const std::shared_ptr<LockWatcher> &watcher = nullptr);
void lock();
bool try_lock();
void unlock();
};
As we mentioned the high level API can automatically extend the lock. However, we might fail to extend the lock, eg connection to Redis is broken. In that case, the auto_extend_err_callback will be called, so that the application can be notified that the lock might no longer be locked, and stop running code in critical section.
The following is the prototype of error callback.
void (std::exception_ptr err);
If error callback is not set (the default behavior), the error will be ignored. And you're on risk of running critical section code with multiple clients.
struct RedMutexOptions {
std::chrono::milliseconds ttl;
std::chrono::milliseconds retry_delay;
bool scripting = true;
};
ttl , otherwise, you might fail to lock or fail to extend the lock.RedMutex::lock repeat trying to lock until it acquires the lock. If it fails, it wait retry_delay before the next retrying. 100 milliseconds by default. LockWatcher watches RedMutex , and try to extend the lock from time to time. You can construct RedMutex with a std::shared_ptr<LockWatcher> , so that it will watch the corresponding Redlock. LockWatcher does the work in a background thread. So creating a LockWatcher object also creates a std::thread . If you want to avoid creating multiple threads, you can construct multiple RedMutex with the same std::shared_ptr<LockWatcher> .
If you don't specify LockWatcher , RedMutex will create one (the default behavior), and start a thread. Although it's expensive to create thread, it's still quite cheap compared to acquiring a distributed lock.
RedMutex is NOT reentrant. If you try to lock a mutex which has already been locked by the current thread, the behavior is undefined.# include < memory >
# include < sw/redis++/redis++.h >
# include < sw/redis++/patterns/redlock.h >
auto redis = std::make_shared<Redis>( " tcp://127.0.0.1 " );
auto redis1 = std::make_shared<Redis>( " tcp://127.0.0.1:7000 " );
auto redis2 = std::make_shared<Redis>( " tcp://127.0.0.1:7001 " );
auto redis3 = std::make_shared<Redis>( " tcp://127.0.0.1:7002 " );
try {
{
// Create a `RedMutex` with a single stand-alone Redis and default settings.
RedMutex mtx (redis, " resource " );
std::lock_guard<RedMutex> lock (mtx);
}
{
// Create a `RedMutex` with multiple stand-alone Redis and default settings.
RedMutex mtx ({redis1, redis2, redis3}, " resource " );
std::lock_guard<RedMutex> lock (mtx);
}
{
RedMutexOptions opts;
opts. ttl = std::chrono::seconds ( 5 );
auto watcher = std::make_shared<LockWatcher>();
// Create a `RedMutex` with auto_extend_err_callback and other options.
RedMutex mtx ({redis1, redis2, redis3}, " resource " ,
[](std::exception_ptr err) {
try {
std::rethrow_exception (err);
} catch ( const Error &e) {
// Notify application code that the lock might no longer be locked.
}
},
opts, watcher);
std::unique_lock<RedMutex> lock (mtx, std::defer_lock);
lock. lock ();
lock. unlock ();
lock. try_lock ();
}
} catch ( const Error &err) {
// handle error.
} // Lua script version:
{
RedLockMutex mtx({redis1, redis2, redis3}, "resource");
// Not locked.
RedLock<RedLockMutex> lock(mtx, std::defer_lock);
// Try to get the lock, and keep 30 seconds.
// It returns the validity time of the lock, i.e. the lock is only
// valid in *validity_time*, after that the lock might be acquired by others.
// If failed to acquire the lock, throw an exception of Error type.
auto validity_time = lock.try_lock(std::chrono::seconds(30));
// Extend the lock before the lock expired.
validity_time = lock.extend_lock(std::chrono::seconds(10));
// You can unlock explicitly.
lock.unlock();
} // If unlock() is not called, the lock will be unlocked automatically when it's destroied.
// Transaction version:
{
RedMutex mtx({redis1, redis2, redis3}, "resource");
RedLock<RedMutex> lock(mtx, std::defer_lock);
auto validity_time = lock.try_lock(std::chrono::seconds(30));
validity_time = lock.extend_lock(std::chrono::seconds(30));
// You can unlock explicitly.
lock.unlock();
}
hset related methods return long long instead of bool . redis-plus-plus is written by sewenew, who is also active on StackOverflow.
Many thanks to all contributors of redis-plus-plus , especially @wingunder.
