redis plus plus
redis-plus-plus 1.3.13
中文交流群
Saya membuat modul Redis, bernama Redis-llm, yang mengintegrasikan LLM (model bahasa besar) dengan Redis. Anda dapat belajar Redis-plus-plus dengan mengajukan pertanyaan dengannya.
Ini adalah pustaka klien C ++ untuk Redis. Ini didasarkan pada hiredis, dan kompatibel dengan C ++ 17, C ++ 14, dan C ++ 11.
Catatan : Saya bukan penutur asli. Jadi, jika dokumentasinya tidak jelas, jangan ragu untuk membuka masalah atau menarik permintaan. Saya akan menanggapi secepatnya.
Cabang utama adalah cabang stabil, yang lulus semua tes. Cabang dev tidak stabil. Jika Anda ingin berkontribusi, silakan buat permintaan tarik di cabang dev.
Karena Redis-plus-plus didasarkan pada hiredis , Anda harus menginstal hiredis terlebih dahulu. Persyaratan versi minimum untuk hiredis adalah v0.12.1 . Namun, rilis stabil terbaru dari Hiredis selalu direkomendasikan.
Catatan : Anda harus memastikan bahwa hanya ada 1 versi hiredis yang diinstal. Kalau tidak, Anda mungkin mendapatkan beberapa masalah kabel. Periksa masalah berikut misalnya: Edisi 135, Edisi 140 dan Edisi 158.
Biasanya, Anda dapat menginstal Hiredis dengan manajer paket C ++, dan itulah cara termudah untuk melakukannya, misalnya sudo apt-get install libhiredis-dev . Namun, jika Anda ingin menginstal kode hiredis terbaru, atau versi yang ditentukan (misalnya dukungan async hiredis v1.0.0 atau lebih baru), Anda dapat menginstalnya dari sumber.
Catatan lagi: Jangan menginstal beberapa versi hiredis.
git clone https://github.com/redis/hiredis.git
cd hiredis
make
make installSecara default, Hiredis diinstal AT /USR /Lokal . Jika Anda ingin menginstal hiredis di lokasi non-default, gunakan perintah berikut untuk menentukan jalur instalasi.
make PREFIX=/non/default/path
make PREFIX=/non/default/path installRedis-plus-plus dibangun dengan cmake.
git clone https://github.com/sewenew/redis-plus-plus.git
cd redis-plus-plus
mkdir build
cd build
cmake ..
make
make install
cd .. Jika hiredis diinstal di lokasi non-default, Anda harus menggunakan CMAKE_PREFIX_PATH untuk menentukan jalur instalasi hiredis . Secara default, Redis-plus-plus diinstal AT /USR /Lokal . Namun, Anda dapat menggunakan CMAKE_INSTALL_PREFIX untuk menginstal Redis-plus-plus di lokasi non-default.
cmake -DCMAKE_PREFIX_PATH=/path/to/hiredis -DCMAKE_INSTALL_PREFIX=/path/to/install/redis-plus-plus .. Karena versi 1.3.0, secara default, Redis-plus-plus dibangun dengan standar -std=c++17 . Sehingga kita dapat menggunakan fitur opsional std :: string_view dan std ::. Namun, itu juga dapat dibangun dengan standar -std=c++11 atau -std=c++14 , dan dalam hal ini, kami memiliki implementasi sederhana kami sendiri dari std::string_view dan std::optional . Untuk secara eksplisit menentukan standar C ++, Anda dapat menggunakan bendera CMake berikut: -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 ..Catatan : Anda harus membangun Redis-plus-plus dan aplikasi Anda dengan standar yang sama, misalnya jika Anda membangun Redis-plus-plus dengan standar C ++ 17, Anda juga harus membangun kode aplikasi Anda dengan standar C ++ 17.
Saat menyusun Redis-plus-plus , itu juga menyusun program pengujian, yang mungkin memakan waktu cukup lama. Namun, Anda dapat menonaktifkan tes bangunan dengan opsi cmake berikut: -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 .. Secara default, Redis-plus-plus membangun perpustakaan statis dan perpustakaan bersama. Jika Anda hanya ingin membangun salah satu dari mereka, Anda dapat menonaktifkan yang lain dengan -DREDIS_PLUS_PLUS_BUILD_STATIC=OFF atau -DREDIS_PLUS_PLUS_BUILD_SHARED=OFF .
Redis-plus-plus membangun pustaka statis dengan opsi -fPIC , yaitu kode independen, secara default. Namun, Anda dapat menonaktifkannya dengan -DREDIS_PLUS_PLUS_BUILD_STATIC_WITH_PIC=OFF .
Sekarang Hiredis memiliki dukungan Windows, dan karena Visual Studio 2017, Visual Studio memiliki dukungan bawaan untuk CMake. Jadi Redis-plus-plus juga mendukung platform Windows sekarang. Ini telah sepenuhnya diuji dengan Visual Studio 2017 dan kemudian menang 10. Saya tidak terbiasa dengan lingkungan Visual Studio, dan dokumen berikut mungkin tidak akurat. Jika Anda terbiasa dengan platform Windows, jangan ragu untuk memperbarui dokumen ini tentang cara menginstal Redis-plus-plus di Windows.
Berikut ini adalah beberapa tautan tentang cara membangun proyek cmake dengan Visual Studio 2017 atau lebih baru. Jika Anda tidak terbiasa dengan itu, Anda sebaiknya membaca instruksi ini terlebih dahulu:
Catatan : IMHO, Dukungan Visual Studio 2017 untuk Proyek CMake tidak terlalu matang, dan saya sarankan Anda untuk membangun Hiredis dan *Redis-plus-plus dengan Visual Studio 2019.
Pertama -tama, Anda perlu mendapatkan kode hiredis terbaru di Master Branch. Versi yang lebih lama mungkin tidak mendukung platform Windows. hiredis 'cmakelists.txt menggunakan metode add_compile_definitions , yang hanya didukung oleh cmake 3.12 atau lebih baru. Namun, versi CMAKE Visual Studio 2017 lebih tua dari itu. Jadi, jika Anda menggunakan Visual Studio 2017, Anda perlu mengomentari baris berikut di file cmakelists.txt:
#IF(WIN32)
# ADD_COMPILE_DEFINITIONS(_CRT_SECURE_NO_WARNINGS WIN32_LEAN_AND_MEAN)
#ENDIF()Anda dapat menggunakan fitur folder terbuka untuk membuka proyek hiredis , dan membangunnya dengan instruksi (tautan) yang disebutkan di atas.
Karena Redis-plus-plus tergantung pada hiredis , kita perlu menentukan jalur instalasi hiredis sebelum membangunnya. Anda dapat menggunakan fitur folder terbuka untuk membuka proyek Redis-plus-plus . Anda perlu mengedit file cmakesetting.json (secara otomatis dihasilkan oleh Visual Studio) untuk mengatur variabel hiredis_header , hiredis_lib dan test_hiredis_lib untuk menentukan jalur instalasi header hiredis, jalur instalasi perpustakaan dinamis hiredis dan jalur instalasi hiredis static library. Berikut ini adalah contoh file 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 "
}
]
}
]
} Kemudian Anda dapat membangunnya instruksi (tautan) yang disebutkan di atas. Jika Anda membangun dengan Visual Studio 2017 dalam mode Debug, Anda mungkin mendapatkan /BIGOBJ ERROR saat membangun tes. Dalam hal ini, Anda dapat menonaktifkan tes bangunan dengan mengatur -DREDIS_PLUS_PLUS_BUILD_TEST=OFF atau membangunnya dalam mode rilis.
CATATAN :
REDIS_PLUS_PLUS_CXX_STANDARD menjadi 11.Jika Anda ingin membangun proyek dengan Visual Studio dan memiliki pertanyaan tentang hal itu, silakan ikuti langkah -langkah di bawah ini. Berikut ini diuji pada komunitas 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 Sejauh ini seharusnya baik -baik saja dengan setiap langkah. Kemudian buka file CMakeLists.txt . Memodifikasi baris berikut dan berkomentar
...
# SET(CMAKE_DEBUG_POSTFIX d)
...Kemudian kembali ke folder proyek sewaan
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 Atur hiredis sebagai Proyek Startup lalu klik Build Solution dalam Mode Debug
Setelah berhasil membangun, salin semua file di bawah Debug ke folder hiredis-lib/lib
Di sini pekerjaan untuk hiredis harus diselesaikan.
Kemudian kembali ke folder redis++ . Terminal terbuka di sini
git clone https: // github.com / sewenew / redis - plus - plus.git
cd redis - plus - plus
mkdir build
cd build Sekarang Anda harus selalu memiliki OpenSSL di PC Anda, jika tidak dapat menggunakan cokelat untuk menginstalnya. Untuk Visual Studio 2022, silakan instal pthread secara terpisah menggunakan vpckg , mengikuti tautan ini
Setelah semua persiapan. Jika Anda ingin mengonversi semua proyek maka
cmake - DCMAKE_PREFIX_PATH = " $ ( ABSOLUTE_PATH ) hiredis-lib " - G " Visual Studio 17 2022 " ..
cd build
. / redis ++ .sln Atur redis++_static sebagai Proyek Startup Lalu klik Build Solution
Sejauh ini Build telah berhasil selesai!
Pada platform Windows, jika kode aplikasi Anda juga perlu menyertakan windows.h . Anda harus memastikan bahwa SW/REDIS ++/REDIS ++. H disertakan sebelum Windows.h . Periksa masalah ini untuk detailnya.
Dukungan dasar untuk membangun paket GNU/Debian disuplai dengan penggunaan CMake. Contoh berikut menunjukkan cara membangun paket Debian:
mkdir build ; cd build
cmake ..
cpack -G DEBAwalan instal dapat dimodifikasi sebagai berikut:
mkdir build ; cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr ..
cpack -G DEBRedis-plus-plus telah sepenuhnya diuji dengan kompiler berikut:
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) Jika Anda membangun Redis -plus -plus dengan -DREDIS_PLUS_PLUS_BUILD_TEST=ON (perilaku default, dan Anda dapat menonaktifkan tes bangunan dengan -DREDIS_PLUS_PLUS_BUILD_TEST=OFF ), Anda akan mendapatkan program pengujian dalam Direktori Build/Test : Test/Test_redis ++ .
Untuk menjalankan tes, Anda perlu mengatur instance Redis, dan cluster Redis. Karena program pengujian akan mengirim sebagian besar perintah Redis ke server dan cluster, Anda perlu mengatur Redis dari versi terbaru. Kalau tidak, tes mungkin gagal. Misalnya, jika Anda mengatur Redis 4.0 untuk pengujian, program pengujian akan gagal ketika mencoba mengirim perintah ZPOPMAX (perintah Redis 5.0) ke server. Jika Anda ingin menjalankan tes dengan versi RedIS lainnya, Anda harus mengomentari perintah yang belum didukung oleh REDIS Anda, dari file sumber uji di Redis-plus-plus/test/src/sw/redis ++/ direktori. Maaf atas ketidaknyamanan ini, dan saya akan memperbaiki masalah ini untuk membuat program pengujian berfungsi dengan versi Redis di masa depan.
CATATAN : Versi terbaru REDIS hanyalah persyaratan untuk menjalankan tes. Bahkan, Anda dapat menggunakan Redis-plus-plus dengan redis versi apa pun, yaitu Redis 2.0 dan di atasnya.
Jangan pernah menjalankan program pengujian dalam advronment produksi, karena kunci, yang dibaca atau ditulis oleh program pengujian, mungkin bertentangan dengan aplikasi Anda.
Untuk menjalankan tes dengan redis dan redis cluster, Anda dapat menjalankan program pengujian dengan perintah berikut:
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_portJika Anda hanya ingin menjalankan tes dengan Redis, Anda hanya perlu menentukan opsi host , port dan auth :
./build/test/test_redis++ -h host -p port -a authDemikian pula, jika Anda hanya ingin menjalankan tes dengan redis cluster, cukup tentukan opsi cluster_node , cluster_port dan auth :
./build/test/test_redis++ -a auth -n cluster_node -c cluster_portSecara default, program pengujian tidak akan menguji menjalankan Redis-plus-plus di lingkungan multi-threads. Jika Anda ingin melakukan tes multi -threads, yang mungkin menghabiskan waktu lama, Anda dapat menentukan opsi -M :
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_port -mJika semua tes telah dilewati, program pengujian akan mencetak pesan berikut:
Pass all testsKalau tidak, itu mencetak pesan kesalahan.
Redis-plus-plus berjalan secepat hiredis , karena ini adalah pembungkus hiredis . Anda dapat menjalankan test_redis ++ dalam mode benchmark untuk memeriksa kinerja di lingkungan Anda.
./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 secara default.5 secara default.100000 secara default.10 secara default.10 secara default. Bechmark akan menghasilkan 100 tombol biner acak untuk pengujian, dan ukuran tombol ini ditentukan oleh KEY_LEN . Ketika patokan berjalan, ia akan membaca/menulis dengan kunci -kunci ini. Jadi jangan pernah menjalankan program pengujian di lingkungan produksi Anda, jika tidak, itu mungkin secara tidak akurat menghapus data Anda.
Setelah menyusun kode, Anda akan mendapatkan perpustakaan bersama dan perpustakaan statis. Karena Redis-plus-plus tergantung pada hiredis , Anda perlu menautkan kedua perpustakaan ke aplikasi Anda. Juga jangan lupa untuk menentukan standar C ++, -std=c++17 , -std=c++14 atau -std=c++11 , serta opsi terkait utas.
Ambil GCC sebagai contoh.
g++ -std=c++17 -o app app.cpp /path/to/libredis++.a /path/to/libhiredis.a -pthread Jika hiredis dan redis-plus-plus diinstal di lokasi non-default, Anda harus menggunakan opsi -I untuk menentukan jalur header.
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 Jika hiredis dan redis-plus-plus diinstal di lokasi non-default, Anda harus menggunakan opsi -I dan -L untuk menentukan jalur header dan pustaka.
g++ -std=c++17 -I/non-default/install/include/path -L/non-default/install/lib/path -o app app.cpp -lredis++ -lhiredis -pthreadSaat menautkan dengan perpustakaan bersama, dan menjalankan aplikasi Anda, Anda mungkin mendapatkan pesan kesalahan berikut:
error while loading shared libraries: xxx: cannot open shared object file: No such file or directory. Itu karena tautan tidak dapat menemukan perpustakaan bersama. Untuk menyelesaikan masalah, Anda dapat menambahkan jalur di mana Anda menginstal perpustakaan hiredis dan redis-plus-plus , ke variabel lingkungan LD_LIBRARY_PATH . Misalnya:
export LD_LIBRARY_PATH= $LD_LIBRARY_PATH :/usr/local/libPeriksa pertanyaan stackoverflow ini untuk detail tentang cara menyelesaikan masalah.
Jika Anda menggunakan CMake untuk membangun aplikasi Anda, Anda perlu menambahkan dependensi hiredis dan redis-plus-plus di cmakelists Anda.
# <---------- 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} )Lihat masalah ini untuk contoh lengkap cmakelists.txt .
Juga, jika Anda menginstal hiredis dan redis-plus-plus di lokasi non-default, Anda perlu menjalankan cmake dengan opsi CMAKE_PREFIX_PATH untuk menentukan jalur instalasi dari dua perpustakaan ini.
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.
}Anda juga dapat melihat redis.h untuk dokumentasi gaya doxygen.
Redis Class memelihara kumpulan koneksi ke server Redis. Jika koneksi rusak, Redis terhubung kembali ke Redis Server secara otomatis.
Anda dapat menginisialisasi instance Redis dengan ConnectionOptions dan ConnectionPoolOptions . ConnectionOptions Menentukan opsi untuk koneksi ke server redis, dan ConnectionPoolOptions menentukan opsi untuk kumpulan Conneciton. ConnectionPoolOptions adalah opsional. Jika tidak ditentukan, Redis mempertahankan satu koneksi ke server 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); CATATAN : Jika Anda mengatur ConnectionOptions::socket_timeout , dan mencoba memanggil perintah pemblokiran, misalnya Redis::brpop , Redis::blpop , Redis::bzpopmax , Redis::bzpopmin , Anda harus memastikan bahwa ConnectionOptions::socket_timeout lebih besar dari batas waktu yang ditentukan dengan perintah blok ini. Kalau tidak, Anda mungkin mendapatkan TimeoutError , dan kehilangan pesan.
Lihat ConnectionOptions dan ConnectionPoolOptions untuk lebih banyak opsi. Juga lihat edisi 80 untuk diskusi tentang kumpulan koneksi.
Catatan : Kelas Redis dapat dipindahkan tetapi tidak dapat disalin.
// auto redis3 = redis1; // this won't compile.
// But it's movable.
auto redis3 = std::move(redis1);Redis-plus-plus juga mendukung penghubung ke server Redis dengan soket domain UNIX.
ConnectionOptions options;
options.type = ConnectionType::UNIX;
options.path = " /path/to/socket " ;
Redis redis (options);Anda juga dapat terhubung ke Redis Server dengan URI:
tcp://[[username:]password@]host[:port][/db]
redis://[[username:]password@]host[:port][/db]
unix://[[username:]password@]path-to-unix-domain-socket[/db]
Skema dan bagian host diperlukan, dan lainnya opsional. Jika Anda terhubung ke Redis dengan soket domain UNIX, Anda harus menggunakan skema UNIX , jika tidak, Anda harus menggunakan skema TCP atau REDIS . Berikut ini adalah daftar nilai default untuk bagian opsional tersebut:
Catatan : Jika kata sandi atau nama pengguna Anda berisi '@', atau nama pengguna Anda berisi ':', Anda tidak dapat membuat objek Redis dengan URI. Karena Redis-plus-plus akan secara keliru mengurai URI. Dalam hal ini, Anda perlu menggunakan ConnectionOptions untuk membuat objek Redis .
Catatan : Redis 6.0 mendukung ACL, dan Anda dapat menentukan nama pengguna untuk koneksi. Namun, sebelum Redis 6.0, Anda tidak dapat melakukan itu.
Juga, opsi koneksi berikut dan opsi kumpulan koneksi dapat ditentukan dengan string kueri URI, mis.
| Pilihan | Parameter | Bawaan |
|---|---|---|
ConnectionOptions::user | pengguna | bawaan |
ConnectionOptions::password | kata sandi | string kosong, yaitu tidak ada kata sandi |
ConnectionOptions::db | db | 0 |
ConnectionOptions::keep_alive | Keep_alive | PALSU |
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 |
CATATAN :
// 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 " ); Sejak Redis 6.0, ini mendukung versi baru protokol Redis, yaitu resp3. Untuk menggunakan protokol baru ini, Anda perlu mengatur ConnectionOptions::resp menjadi 3.
ConnectionOptions opts;
opts.resp = 3;
// Set other options...
Secara default, ConnectionOptions::resp adalah 2, yaitu menggunakan RESP versi 2. Sejauh ini, hanya versi 2 dan 3 yang didukung, dan perilaku tidak ditentukan, jika Anda mengatur ConnectionOptions::resp ke nomor lain.
Catatan : Untuk menggunakan protokol baru ini, Anda perlu menginstal Hiredis terbaru (bahkan Hiredis-V1.0.2 memiliki bug pada dukungan resp3).
Koneksi di kolam dibuat dengan malas. Ketika kumpulan koneksi diinisialisasi, yaitu konstruktor Redis , Redis tidak terhubung ke server. Sebaliknya, itu terhubung ke server hanya ketika Anda mencoba mengirim perintah. Dengan cara ini, kita dapat menghindari koneksi yang tidak perlu. Jadi jika ukuran kolam adalah 5, tetapi jumlah koneksi bersamaan maksimal adalah 3, hanya akan ada 3 koneksi di kolam.
Anda tidak perlu memeriksa apakah objek Redis terhubung ke server dengan sukses. Jika Redis gagal membuat koneksi ke server Redis, atau koneksi rusak pada suatu waktu, itu melempar pengecualian Error tipe ketika Anda mencoba mengirim perintah dengan Redis . Bahkan ketika Anda mendapatkan pengecualian, yaitu koneksi rusak, Anda tidak perlu membuat objek Redis baru. Anda dapat menggunakan kembali objek Redis untuk mengirim perintah, dan objek Redis akan mencoba untuk terhubung kembali ke server secara otomatis. Jika berhasil terhubung kembali, ia mengirim perintah ke server. Kalau tidak, ia melempar pengecualian lagi.
Lihat bagian Pengecualian untuk detail tentang pengecualian.
Tidak murah untuk membuat objek Redis , karena akan membuat koneksi baru ke Redis Server. Jadi, Anda sebaiknya menggunakan kembali objek Redis sebanyak mungkin. Juga, aman untuk memanggil fungsi anggota Redis di lingkungan multi-thread, dan Anda dapat berbagi objek Redis di banyak utas.
// 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 juga memiliki dukungan TLS. Namun, untuk menggunakan fitur ini, Anda perlu mengaktifkannya saat membangun Hiredis dan Redis-plus-plus .
Catatan : Sejauh ini, fitur TLS belum diuji pada platform Windows. Saya akan memperbaikinya di masa depan.
Saat membangun hiredis dengan dukungan TLS, Anda perlu mengunduh hiredis dari versi v1.0.0 atau terakhir, dan tentukan bendera USE_SSL=1 :
make PREFIX=/non/default/path USE_SSL=1
make PREFIX=/non/default/path USE_SSL=1 install Maka Anda dapat membangun Redis-plus-plus untuk mengaktifkan dukungan TLS dengan menentukan -DREDIS_PLUS_PLUS_USE_TLS=ON Option:
cmake -DREDIS_PLUS_PLUS_USE_TLS=ON ..Untuk terhubung ke Redis dengan dukungan TLS, Anda perlu menentukan opsi koneksi berikut:
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 Meskipun tls.cert dan tls.key adalah opsional, jika Anda menentukan salah satunya, Anda juga harus menentukan yang lain. Alih -alih menentukan tls.cacert , Anda juga dapat menentukan tls.cacertdir ke direktori tempat sertifikat disimpan.
Opsi-opsi ini sama dengan argumen baris perintah terkait redis-cli TLS, sehingga Anda juga dapat menjalankan redis-cli --help untuk mendapatkan penjelasan terperinci dari opsi-opsi ini.
Kemudian Anda dapat menggunakan ConnectionOptions ini untuk membuat objek Redis untuk terhubung ke server Redis dengan dukungan TLS.
Catatan : Saat membangun kode aplikasi Anda, Anda juga perlu menautkannya dengan libhiredis.a , libhiredis_ssl.a , libredis++.a (atau pustaka bersama yang sesuai), -lssl dan -lcrypto .
Secara default, Redis-plus-plus secara otomatis menginisialisasi pustaka OpenSSL, IE panggilan SSL_library_init dan menginisialisasi kunci jika diperlukan. Namun, kode aplikasi Anda mungkin sudah menginisialisasi pustaka OpenSSL. Dalam hal ini, Anda dapat menghubungi tls::disable_auto_init() untuk menonaktifkan inisialisasi. Anda harus memanggil fungsi ini hanya sekali dan memanggilnya sebelum operasi Redis-plus-plus lainnya. Kalau tidak, perilaku tidak terdefinisi.
Sejak Hiredis v1.1.0, mendukung melewatkan verifikasi sertifikat. Jika Anda ingin menggunakan fitur ini dengan Redis-plus-plus , Anda dapat memeriksa masalah ini sebagai contoh.
Anda dapat mengirim perintah Redis melalui objek Redis . Redis memiliki satu atau lebih metode (kelebihan beban) untuk setiap perintah Redis. Metode ini memiliki nama yang sama (lebih rendah) dengan perintah yang sesuai. Misalnya, kami memiliki 3 metode kelebihan beban untuk perintah 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);Dengan parameter input, metode ini membangun perintah Redis berdasarkan protokol Redis, dan mengirim perintah ke server Redis. Kemudian secara sinkron menerima balasan, menguraikannya, dan kembali ke penelepon.
Mari kita lihat lebih dekat parameter metode ini dan nilai mengembalikan.
Sebagian besar metode ini memiliki parameter yang sama dengan perintah yang sesuai. Berikut ini adalah daftar jenis parameter:
| Tipe parameter | Penjelasan | Contoh | Catatan |
|---|---|---|---|
| StringView | Parameter tipe string. Biasanya digunakan untuk kunci, nilai, nama anggota, nama lapangan dan sebagainya | Bool Redis :: HSET (Const StringView & Key, Const StringView & Field, Const StringView & Val) | Lihat bagian StringView untuk detail di StringView |
| lama | Parameter tipe integer. Biasanya digunakan untuk indeks (misalnya perintah daftar) atau integer | void ltrim (const stringview & key, start panjang, berhenti panjang) panjang panjang (const stringview & kunci, penurunan panjang panjang) | |
| dobel | Parameter tipe titik mengambang. Biasanya digunakan untuk skor (misalnya perintah set yang diurutkan) atau jumlah tipe titik mengambang | Double IncrbyFloat (Const StringView & Key, Double Increment) | |
| std :: chrono :: durasi std :: chrono :: time_point | Parameter terkait waktu | bool kedaluwarsa (const stringview & key, const std :: chrono :: detik & timeout) Bool Expireat (Const StringView & Key, Const Std :: Chrono :: Time_Point <Std :: Chrono :: System_Clock, Std :: Chrono :: Seconds> & TP) | |
| std :: pair <StringView, StringView> | Digunakan untuk pasangan redis hash (bidang, nilai) | bool hset (const stringview & key, const std :: pair <stringView, stringView> & item) | |
| std :: pair <double, double> | Digunakan untuk pasangan redis geo (bujur, lintang) | OptionAllonglong Georadius (Const StringView & Key, const std :: pair <double, double> & location, double radius, unit geounit, const stringview & destination, bool store_dist, jumlah panjang panjang) | |
| sepasang iterator | Gunakan sepasang iterator untuk menentukan berbagai input, sehingga kami dapat meneruskan data dalam wadah STL ke metode ini | Template <Input Typename> del panjang panjang (input pertama, input terakhir) | Lemparkan pengecualian, jika itu jarak kosong, IE First == terakhir |
| std :: initializer_list <T> | Gunakan daftar inisialisasi untuk menentukan batch input | Template <typename t> Long Long Del (std :: initializer_list <T> il) | |
| beberapa opsi | Opsi untuk beberapa perintah | UpdateType , template <typename t> class boundedinterval | Lihat command_options.h untuk detailnya |
std :: string_view adalah pilihan yang baik untuk tipe parameter string hanya baca. std::string_view hanya diperkenalkan dalam standar C ++ 17, jadi jika Anda membangun redis -plus -plus dengan -std=c++11 (yaitu dengan menentukan -DREDIS_PLUS_PLUS_CXX_STANDARD=11 dengan perintah cmake) atau -std=c++14 standar implementasi std::string_view STD :: STD :: STREIWE: StringView : STRINE. Anda dapat membangun Redis-plus-plus dengan standar -std=c++17 (yaitu perilaku default), yang akan menyediakan std::string_view secara asli. Implementasi StringView kemudian akan diabaikan dengan aliasing ke std::string_view . Ini dilakukan di dalam pustaka Redis-plus-plus dengan: using StringView = std::string_view .
Karena ada konversi dari std::string dan string c-style ke StringView , Anda dapat meneruskan string std::string atau c-style ke metode yang membutuhkan parameter 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 " );Protokol Redis mendefinisikan 5 jenis balasan:
long long . Juga balasan ini mungkin nol . Misalnya, ketika Anda mencoba GET nilai kunci yang tidak ada, Redis mengembalikan balasan string bulk null .
Seperti yang kami sebutkan di atas, balasan diuraikan menjadi nilai pengembalian dari metode ini. Berikut ini adalah daftar jenis pengembalian:
| Tipe pengembalian | Penjelasan | Contoh | Catatan |
|---|---|---|---|
| ruang kosong | Balas status yang harus selalu mengembalikan serangkaian "ok" | Ganti nama , setex | |
| std :: string | Balas status yang tidak selalu mengembalikan "ok", dan balasan string massal | Ping , info | |
| bool | Balas integer yang selalu mengembalikan 0 atau 1 | Kedaluwarsa , hset | Lihat bagian Nilai Pengembalian Boolean untuk arti nilai pengembalian boolean |
| lama | Balas integer yang tidak selalu mengembalikan 0 atau 1 | Del , Tambahkan | |
| dobel | Balas string curah yang mewakili ganda | IncrbyFloat , Zincrby | |
| std :: pair | Balas array dengan tepat 2 elemen. Karena nilai pengembalian selalu merupakan array dari 2 elemen, kami mengembalikan 2 elemen sebagai elemen pertama dan kedua std::pair | Blpop | |
| std :: tuple | Balas array dengan panjang tetap dan memiliki lebih dari 2 elemen. Karena panjang array yang dikembalikan diperbaiki, kami mengembalikan array sebagai std::tuple | BZPOPMAX | |
| output iterator | General Array Reply dengan panjang non-fixed/dinamis. Kami menggunakan antarmuka seperti STL untuk mengembalikan balasan array semacam ini, sehingga Anda dapat memasukkan nilai pengembalian ke dalam wadah STL dengan mudah | Mget , lrange | Juga, terkadang jenis output iterator memutuskan opsi mana yang akan dikirim dengan perintah. Lihat bagian Contoh untuk detailnya |
| Opsional <t> | Untuk balasan tipe T yang mungkin nol | Dapatkan , LPOP , BLPOP , BZPOPMAX | Lihat bagian opsional untuk detail tentang Optional<T> |
| Varian <args ...> | Untuk balasan yang mungkin memiliki serval yang berbeda | Statistik Memori | Catatan: Sejauh ini, jenis ini hanya didukung saat menyusun Redis-plus-plus dengan standar C ++ 17. Ini biasanya digunakan dengan antarmuka perintah generik. Lihat bagian varian untuk detail tentang Variant<Args...> |
| Wadah STL | Balas Array Umum | Config Get | Iterator output dan wadah STL digunakan untuk balasan array. Perbedaannya adalah bahwa wadah STL biasanya digunakan dengan antarmuka perintah generik. Lihat bagian STL Container Misalnya |
Jenis pengembalian beberapa metode, misalnya EXPIRE , HSET , adalah bool . Jika metode ini mengembalikan false , itu tidak berarti bahwa Redis gagal mengirim perintah ke server Redis. Sebaliknya, itu berarti bahwa Redis Server mengembalikan balasan integer , dan nilai balasannya adalah 0 . Dengan demikian, jika metode ini mengembalikan true , itu berarti bahwa Redis Server mengembalikan balasan integer , dan nilai balasannya adalah 1 . Anda dapat memeriksa Redis Command Manual untuk apa yang dilakukan 0 dan 1 .
Misalnya, ketika kami mengirim perintah EXPIRE ke server redis, ia mengembalikan 1 jika batas waktu diatur, dan mengembalikan 0 jika kunci tidak ada. Dengan demikian, jika batas waktu ditetapkan, Redis::expire Returns true , dan jika kunci tidak ada, Redis::expire Returns false .
Jadi, jangan pernah menggunakan nilai pengembalian untuk memeriksa apakah perintah tersebut telah berhasil dikirim ke server Redis. Sebaliknya, jika Redis gagal mengirim perintah ke server, ia melempar pengecualian Error tipe. Lihat bagian Pengecualian untuk detail tentang pengecualian.
std :: opsional adalah opsi yang baik untuk jenis pengembalian, jika Redis mungkin mengembalikan balasan nol . Namun, std::optional diperkenalkan dalam standar C ++ 17, dan jika Anda membangun Redis -plus -plus dengan -std=c++11 standar (yaitu dengan menentukan -DREDIS_PLUS_PLUS_CXX_STANDARD=11 dengan perintah cmake), kami mengimplementasikan versi sederhana kami sendiri, yaitu template Optional<T> . Sebaliknya, jika Anda membangun Redis-plus-plus dengan -std=c++17 standar (yaitu perilaku default), Anda dapat menggunakan std::optional , dan kami memiliki alias untuk itu: template <typename T> using Optional = std::optional<T> .
Ambil Perintah Get dan MGet misalnya:
// 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.
}
} Kami juga memiliki beberapa typedef untuk beberapa 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 :: Varian adalah pilihan yang baik untuk jenis pengembalian, jika balasannya mungkin dari berbagai jenis. Misalnya, perintah MEMORY STATS mengembalikan balasan array, yang pada kenyataannya, merupakan peta pasangan konfigurasi nilai kunci:
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 "
... Namun, seperti yang Anda lihat, bagian nilai dari hasil mungkin tipe panjang (kunci: puncak.alokasi ), ganda (kunci: dataset.percentage ) atau bahkan peta (kunci: db.0 ). Jadi Anda tidak bisa hanya menguraikan hasilnya menjadi std::unordered_map<std::string, long long> atau std::unordered_map<std::string, double> . Solusi adalah untuk menguraikan hasilnya menjadi tuple , namun, solusi tuple ini jelek dan rentan kesalahan. Periksa masalah ini untuk detailnya.
Dalam hal ini, Variant , yang merupakan typedef dari std::variant jika Anda membangun redis-plus-plus dengan standar C ++ 17, sangat membantu. Anda dapat menguraikan hasilnya menjadi 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 " ); Ada beberapa batasan dukungan Variant :
Variant , tidak dapat memiliki item duplikat, misalnya Variant<double, long long, double> tidak akan berfungsi.double harus ditempatkan sebelum std::string . Karena balasan double , pada kenyataannya, membalas string, dan ketika parsing varian, kami mencoba untuk menguraikan balasan ke jenis yang cocok pertama, ditentukan dengan argumen tipe dari kiri ke kanan. Jadi jika double ditempatkan setelah std::string , yaitu di sisi kanan std::string , balasan akan selalu diuraikan ke std::string .Periksa juga bagian perintah generik untuk lebih banyak contoh pada antarmuka perintah generik.
Saat menggunakan antarmuka perintah generik, alih -alih parsing balasan ke output iterator, Anda juga dapat menguraikannya ke dalam wadah STL.
auto r = Redis( " tcp://127.0.0.1 " );
auto v = r.command<std::unordered_map<std::string, std::string>>( " config " , " get " , " * " );Periksa juga bagian perintah generik untuk lebih banyak contoh pada antarmuka perintah generik.
Mari kita lihat beberapa contoh tentang cara mengirim perintah ke server redis.
// ***** 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 ;
}
}Terkadang jenis output iterator memutuskan opsi mana yang akan dikirim dengan perintah.
// 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));Silakan lihat Redis.h untuk referensi dan contoh API gaya doxygen, dan lihat tes untuk contoh lain.
Redis melempar pengecualian jika menerima balasan kesalahan atau sesuatu yang buruk terjadi, misalnya gagal membuat koneksi ke server, atau koneksi ke server rusak. Semua pengecualian berasal dari kelas Error . Lihat kesalahan.h untuk detailnya.
Error : Kesalahan generik. Ini berasal dari std::exception , dan itu juga kelas dasar dari pengecualian lainnya.IoError : Ada beberapa kesalahan IO dengan koneksi.TimeoutError : Operasi baca atau tulis sudah habis waktunya. Ini adalah kelas IoError yang diturunkan.ClosedError : Server Redis menutup koneksi.ProtoError : Perintah atau balasan tidak valid, dan kami tidak dapat memprosesnya dengan protokol Redis.OomError : Perpustakaan Hiredis mendapat kesalahan di luar memori.ReplyError : Server Redis mengembalikan balasan kesalahan, misalnya kami mencoba menelepon redis::lrange pada hash redis.WatchError : Watched Key telah dimodifikasi. Lihat bagian Tonton untuk detailnya. Catatan : Balas nol tidak diambil sebagai pengecualian. Misalnya, jika kami mencoba GET kunci yang tidak ada, kami akan mendapatkan balasan string curah null . Alih -alih melempar pengecualian, kami mengembalikan balasan nol sebagai objek Optional<T> nol. Juga lihat bagian opsional.
Biasanya, ketika pengecualian terjadi, Anda tidak perlu membuat objek Redis . Pengecualian aman, dan Anda dapat menggunakan kembali objek Redis . Bahkan jika koneksi ke server Redis rusak, dan itu melempar beberapa pengecualian, katakanlah, IoError . Lain kali ketika Anda mengirim perintah dengan objek Redis , ia akan mencoba untuk terhubung kembali ke Redis Server secara otomatis. Aturan ini juga berlaku untuk RedisCluster . Namun, jika Pipeline , Transcation dan Subscriber melempar pengecualian, Anda perlu menghancurkan objek, dan membuat yang baru. Lihat dokumentasi yang sesuai untuk detailnya.
Berikut ini adalah contoh tentang cara menangkap pengecualian ini:
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
} Terlalu banyak perintah Redis, kami belum menerapkan semuanya. Namun, Anda dapat menggunakan metode Redis::command generik untuk mengirim perintah apa pun ke Redis. Tidak seperti pustaka klien lainnya, Redis::command tidak menggunakan format string untuk menggabungkan argumen perintah ke dalam string perintah. Sebaliknya, Anda dapat secara langsung meneruskan argumen perintah dari tipe StringView atau tipe aritmatika sebagai parameter Redis::command . Untuk alasan mengapa kami tidak menggunakan string format, silakan lihat diskusi ini.
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)); Catatan : Nama beberapa perintah Redis disusun dengan dua string, misalnya klien setName . Dalam hal ini, Anda perlu melewati dua string ini sebagai dua argumen untuk 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"); Seperti yang saya sebutkan di komentar, perintah SET tidak selalu mengembalikan 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.
CATATAN :
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.
CATATAN :
# 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.
