redis plus plus
redis-plus-plus 1.3.13
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redis-llmという名前のRedisモジュールを作成します。Redis-llmは、LLMS（大規模な言語モデル）とRedisを統合します。質問をすることで、Redis-Plus-Plusを学ぶことができます。
これは、RedisのC ++クライアントライブラリです。 Hiredisに基づいており、C ++ 17、C ++ 14、およびC ++ 11と互換性があります。
注：私はネイティブスピーカーではありません。したがって、ドキュメントが不明な場合は、お気軽に問題を開いたり、リクエストをプルしたりしてください。できるだけ早く応答します。
マスターブランチは、すべてのテストに合格する安定したブランチです。開発部門は不安定です。貢献したい場合は、Dev Branchにプルリクエストを作成してください。
Redis-Plus-PlusはHiredisに基づいているため、最初にHiredisをインストールする必要があります。 Hiredisの最小バージョン要件はv0.12.1です。ただし、 Hiredisの最新の安定したリリースを常にお勧めします。
注：Hiredisのバージョンのみがインストールされていることを確認する必要があります。そうしないと、いくつかの有線の問題が発生する可能性があります。次の問題を確認します。たとえば、第135号、第140号、および第158号を確認してください。
通常、C ++パッケージマネージャーでHiredisをインストールできます。これが最も簡単な方法です。たとえばsudo apt-get install libhiredis-devなどです。ただし、最新のHiredisコード、または指定されたバージョン（AsyncサポートニーズHiredis v1.0.0以降）をインストールする場合は、ソースからインストールできます。
もう一度注意：Hiredisの複数のバージョンをインストールしないでください。
git clone https://github.com/redis/hiredis.git
cd hiredis
make
make installデフォルトでは、 Hiredisは/usr /localにインストールされます。非デフォルトの場所にHiredisをインストールする場合は、次のコマンドを使用してインストールパスを指定します。
make PREFIX=/non/default/path
make PREFIX=/non/default/path installRedis-Plus-PlusはCmakeで構築されています。
git clone https://github.com/sewenew/redis-plus-plus.git
cd redis-plus-plus
mkdir build
cd build
cmake ..
make
make install
cd .. Hiredisが非Defaultの場所にインストールされている場合は、 CMAKE_PREFIX_PATHを使用してHiredisのインストールパスを指定する必要があります。デフォルトでは、 Redis-Plus-Plusは/USR /Localにインストールされています。ただし、 CMAKE_INSTALL_PREFIXを使用して、非デフォルトの場所にRedis-Plus-Plusをインストールできます。
cmake -DCMAKE_PREFIX_PATH=/path/to/hiredis -DCMAKE_INSTALL_PREFIX=/path/to/install/redis-plus-plus ..バージョン1.3.0以降、デフォルトでは、 Redis-Plus-Plusは-std=c++17標準で構築されています。 STD :: String_ViewおよびSTD ::オプション機能を使用できるように。ただし、 -std=c++11または-std=c++14標準で構築することもできます。その場合、 std::string_viewおよびstd::optionalの独自の簡単な実装があります。 C ++標準を明示的に指定するために、次のCmakeフラグを使用できます： -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 ..注：同じ標準でRedis-Plus-Plusとアプリケーションを構築する必要があります。たとえば、C ++ 17標準でRedis-Plus-Plusを構築する場合は、C ++ 17標準でアプリケーションコードを構築する必要があります。
Redis-Plus-Plusをコンパイルするときは、テストプログラムもコンパイルします。これには時間がかかる場合があります。ただし、次のcmakeオプションで構築テストを無効にすることができます： -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 ..デフォルトでは、 Redis-Plus-Plusは静的ライブラリと共有ライブラリの両方を構築します。それらのいずれかを構築したい場合は、 -DREDIS_PLUS_PLUS_BUILD_STATIC=OFFまたは-DREDIS_PLUS_PLUS_BUILD_SHARED=OFFで他のものを無効にすることができます。
Redis-Plus-Plusは、 -fPICオプションを備えた静的ライブラリ、つまり、デフォルトで独立したコードの位置を構築します。ただし、 -DREDIS_PLUS_PLUS_BUILD_STATIC_WITH_PIC=OFFで無効にすることができます。
HiredisにはWindowsサポートがあり、Visual Studio 2017以来、Visual StudioにはCMakeのサポートが組み込まれています。そのため、 Redis-Plus-PlusはWindowsプラットフォームもサポートしています。 Visual Studio 2017で完全にテストされ、後にWin 10でテストされています。Visual Studio環境には精通していません。次のドキュメントは正確ではない可能性があります。 Windowsプラットフォームに精通している場合は、WindowsにRedis-Plus-Plusをインストールする方法についてこのドキュメントを自由に更新してください。
以下は、Visual Studio 2017以降でCMakeプロジェクトを構築する方法に関するいくつかのリンクです。あなたがそれに慣れていないなら、あなたは最初にこれらの指示を読む方が良いでしょう：
注：IMHO、Visual Studio 2017のCMAKEプロジェクトのサポートはあまり成熟しておらず、Visual Studio 2019でHiredisと *Redis-Plus-Plusを構築することをお勧めします。
まず、マスターブランチで最新のHiredisコードを取得する必要があります。古いバージョンはWindowsプラットフォームをサポートしていない場合があります。 hiredisのcmakelists.txtは、 add_compile_definitionsメソッドを使用します。これは、Cmake 3.12以降のみでサポートされています。ただし、Visual Studio 2017のCmakeバージョンはそれよりも古いです。したがって、Visual Studio 2017を使用している場合は、cmakelists.txtファイルに次の行にコメントする必要があります。
#IF(WIN32)
# ADD_COMPILE_DEFINITIONS(_CRT_SECURE_NO_WARNINGS WIN32_LEAN_AND_MEAN)
#ENDIF()オープンフォルダー機能を使用して、 Hiredisプロジェクトを開き、上記の手順（リンク）で作成できます。
Redis-Plus-PlusはHiredisに依存しているため、構築する前にHiredisのインストールパスを指定する必要があります。 Openフォルダー機能を使用して、 Redis-Plus-Plusプロジェクトを開くことができます。 cmakesetting.jsonファイル（Visual Studioによって自動的に生成）を編集して、 Hiredis_header 、 Hiredis_lib 、およびtest_hiredis_lib変数を設定する必要があります。以下は、 cmakesetting.jsonファイルの例です。
{
"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 "
}
]
}
]
}次に、上記の指示（リンク）を作成できます。デバッグモードでVisual Studio 2017を使用して構築する場合は、テストを構築するときに /BigOBJエラーが発生する可能性があります。この場合、 -DREDIS_PLUS_PLUS_BUILD_TEST=OFFを設定するか、リリースモードで構築することにより、構築テストを無効にできます。
注記：
REDIS_PLUS_PLUS_CXX_STANDARD cmakeオプションを11に設定できます。Visual Studioでプロジェクトを構築し、それについて質問をしたい場合は、以下の手順に従ってください。以下は、Visual Studio 2022 Communityでテストされています。
# 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これまでのところ、各ステップでは問題ありません。次に、 CMakeLists.txtファイルを開きます。次の行を変更し、コメントしてください
...
# SET(CMAKE_DEBUG_POSTFIX d)
...次に、Hiredis Projectフォルダーに戻ります
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スタートアッププロジェクトとしてhiredisを設定し、デバッグモードでBuild Solutionをクリックします
成功した後、 Debugの下のすべてのファイルをhiredis-lib/libフォルダーにコピーします
ここで、Hiredisの作業を終了する必要があります。
次に、 redis++フォルダーに戻ります。ここからターミナルを開きます
git clone https: // github.com / sewenew / redis - plus - plus.git
cd redis - plus - plus
mkdir build
cd buildこれで、PCで常にOpenSSLが必要なはずです。そうでなければ、チョコレートを使用してインストールできます。 Visual Studio 2022については、このリンクに従ってvpckgを使用してPTHREADを個別にインストールしてください
すべての準備の後。すべてのプロジェクトを変換したい場合
cmake - DCMAKE_PREFIX_PATH = " $ ( ABSOLUTE_PATH ) hiredis-lib " - G " Visual Studio 17 2022 " ..
cd build
. / redis ++ .sln redis++_static起動プロジェクトとして設定し、 Build Solutionをクリックします
これまでのところ、ビルドが正常に終了しました！
Windowsプラットフォームでは、アプリケーションコードにもwindows.hを含める必要がある場合。 sw/redis ++/redis++。hがwindows.hの前に含まれることを確認する必要があります。詳細については、この問題を確認してください。
GNU/Debianパッケージを構築するための基本的なサポートは、Cmakeを使用して提供されます。次の例は、Debianパッケージの構築方法を示しています。
mkdir build ; cd build
cmake ..
cpack -G DEBインストールプレフィックスは次のように変更できます。
mkdir build ; cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr ..
cpack -G DEBRedis-Plus-Plusは、次のコンパイラーで完全にテストされています。
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) -DREDIS_PLUS_PLUS_BUILD_TEST=ON （デフォルトの動作を使用してRedis -Plus -Plusを構築し、 -DREDIS_PLUS_PLUS_BUILD_TEST=OFFでビルディングテストを無効にすることができれば、ビルド/テストディレクトリでテストプログラムを取得します。
テストを実行するには、RedisインスタンスとRedisクラスターを設定する必要があります。テストプログラムはRedisコマンドのほとんどをサーバーとクラスターに送信するため、最新バージョンのRedisをセットアップする必要があります。それ以外の場合、テストが失敗する可能性があります。たとえば、テスト用にRedis 4.0をセットアップすると、 ZPOPMAXコマンド（Redis 5.0コマンド）をサーバーに送信しようとすると、テストプログラムが失敗します。他のRedisバージョンでテストを実行する場合は、 Redis-Plus-Plus/Test/SRC/SW/REDIS ++/ディレクトリのテストソースファイルから、Redisによってサポートされていないコマンドをコメントする必要があります。ご不便をおかけして申し訳ありませんが、この問題を修正して、将来のRedisのバージョンでテストプログラムを機能させるようにします。
注：Redisの最新バージョンは、テストを実行するための要件にすぎません。実際、あらゆるバージョンのRedis、すなわちRedis 2.0以上のRedis-Plus-Plusを使用できます。
テストプログラムが読み取ったり書いたりするキーがアプリケーションと矛盾する可能性があるため、生産環境でテストプログラムを実行しないでください。
RedisクラスターとRedisクラスターの両方でテストを実行するには、次のコマンドでテストプログラムを実行できます。
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_portRedisでテストのみを実行する場合は、ホスト、ポート、およびAUTHのオプションを指定する必要があります。
./build/test/test_redis++ -h host -p port -a auth同様に、Redis Clusterでテストを実行する場合のみ、 cluster_node 、 cluster_port、およびauthオプションを指定します。
./build/test/test_redis++ -a auth -n cluster_node -c cluster_portデフォルトでは、テストプログラムでは、マルチスレッド環境でRedis-Plusプラスを実行していません。長い時間がかかる可能性のあるマルチスレッドテストを実行したい場合は、 -mオプションを指定できます。
./build/test/test_redis++ -h host -p port -a auth -n cluster_node -c cluster_port -mすべてのテストが渡された場合、テストプログラムは次のメッセージを印刷します。
Pass all testsそれ以外の場合は、エラーメッセージを印刷します。
Redis-Plus-Plusは、 Hiredisのラッパーであるため、 Hiredisと同じくらい速く実行されます。 Test_redis ++をベンチマークモードで実行して、環境でのパフォーマンスを確認できます。
./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デフォルトで。5デフォルトで。100000 。10デフォルトで。10デフォルトで。 Bechmarkは、テスト用の100ランダムバイナリキーを生成し、これらのキーのサイズはKey_Lenによって指定されます。ベンチマークが実行されると、これらのキーを使用して読み取り/書き込みになります。したがって、生産環境でテストプログラムを実行しないでください。そうしないと、データが不定的に削除される可能性があります。
コードをコンパイルした後、共有ライブラリと静的ライブラリの両方が取得されます。 Redis-Plus-PlusはHiredisに依存するため、両方のライブラリをアプリケーションにリンクする必要があります。また、C ++標準、 -std=c++17 、 -std=c++14または-std=c++11 、およびスレッド関連オプションを指定することを忘れないでください。
例としてGCCを取ります。
g++ -std=c++17 -o app app.cpp /path/to/libredis++.a /path/to/libhiredis.a -pthread HiredisとRedis-Plus-Plusが非デフォルトの場所にインストールされている場合は、 -Iオプションを使用してヘッダーパスを指定する必要があります。
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 HiredisとRedis-Plus-Plusが非デフォルトの場所にインストールされている場合は、 -Iおよび-Lオプションを使用して、ヘッダーとライブラリパスを指定する必要があります。
g++ -std=c++17 -I/non-default/install/include/path -L/non-default/install/lib/path -o app app.cpp -lredis++ -lhiredis -pthread共有ライブラリとリンクしてアプリケーションを実行すると、次のエラーメッセージが表示される場合があります。
error while loading shared libraries: xxx: cannot open shared object file: No such file or directory.これは、リンカーが共有ライブラリを見つけることができないためです。問題を解決するために、 HiredisとRedis-Plus-PlusライブラリをLD_LIBRARY_PATH環境変数にインストールしたパスを追加できます。例えば：
export LD_LIBRARY_PATH= $LD_LIBRARY_PATH :/usr/local/lib問題を解決する方法の詳細については、このstackoverflowの質問を確認してください。
cmakeを使用してアプリケーションを構築する場合は、 cmakelists.txtにHiredisとRedis-Plus-Plus依存関係を追加する必要があります。
# <---------- 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} )cmakelists.txtの完全な例については、この問題を参照してください。
また、非デフォルトの場所にHiredisとRedis-Plus-Plusをインストールした場合、 CMAKE_PREFIX_PATHオプションでCMAKEを実行して、これら2つのライブラリのインストールパスを指定する必要があります。
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.
}Doxygenスタイルのドキュメントについては、Redis.hを見ることもできます。
Redisクラスは、Redisサーバーへの接続プールを維持します。接続が壊れている場合、 Redis Redisサーバーに自動的に再接続します。
ConnectionOptionsとConnectionPoolOptionsを使用してRedisインスタンスを初期化できます。 ConnectionOptions Redisサーバーへの接続のオプションを指定し、 ConnectionPoolOptions Connecitonプールのオプションを指定します。 ConnectionPoolOptionsオプションです。指定されていない場合、 Redis Redisサーバーへの単一の接続を維持します。
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);注： ConnectionOptions::socket_timeoutを設定し、ブロックコマンドを呼び出す場合、例： Redis::brpop 、 Redis::blpop 、Redis :: Redis::bzpopmax Redis::bzpopminなど、 ConnectionOptions::socket_timeoutがこれらのブロックコマンドで指定されたタイムアウトよりも大きいことを確認する必要があります。それ以外の場合は、 TimeoutErrorを取得し、メッセージを失う可能性があります。
その他のオプションについては、ConnectionOptionsとConnectionPooloptionsを参照してください。接続プールに関する議論については、問題80も参照してください。
注： Redisクラスは移動可能ですが、コピーできません。
// auto redis3 = redis1; // this won't compile.
// But it's movable.
auto redis3 = std::move(redis1);Redis-Plus-Plusは、 UNIXドメインソケットを使用してRedisサーバーに接続することもサポートしています。
ConnectionOptions options;
options.type = ConnectionType::UNIX;
options.path = " /path/to/socket " ;
Redis redis (options);URIを使用してRedisサーバーに接続することもできます。
tcp://[[username:]password@]host[:port][/db]
redis://[[username:]password@]host[:port][/db]
unix://[[username:]password@]path-to-unix-domain-socket[/db]
スキームとホストパーツが必要であり、その他はオプションです。 UNIXドメインソケットを使用してRedisに接続している場合は、 UNIXスキームを使用する必要があります。そうしないと、 TCPまたはRedisスキームを使用する必要があります。以下は、これらのオプションパーツのデフォルト値のリストです。
注：パスワードまたはユーザー名に '@'が含まれている場合、またはユーザー名に '：'が含まれている場合、 RedisオブジェクトをURIで作成することはできません。 Redis-Plus-PlusはURIを誤って解析するためです。この場合、 ConnectionOptionsを使用してRedisオブジェクトを構築する必要があります。
注：Redis 6.0はACLをサポートし、接続のユーザー名を指定できます。ただし、Redis 6.0の前に、それはできません。
また、次の接続オプションと接続プールオプションは、URIのクエリ文字列、例：tcp：//127.0.0.1？keep_alive = true＆socket_timeout = 100ms＆connect_timeout = 100msで指定できます。
| オプション | パラメーター | デフォルト |
|---|---|---|
ConnectionOptions::user | ユーザー | デフォルト |
ConnectionOptions::password | パスワード | 空の文字列、すなわちパスワードはありません |
ConnectionOptions::db | DB | 0 |
ConnectionOptions::keep_alive | Keep_alive | 間違い |
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 |
注記：
// 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 " ); Redis 6.0以降、Redisプロトコルの新しいバージョン、つまりResp3をサポートしています。この新しいプロトコルを使用するには、 ConnectionOptions::respを3に設定する必要があります。
ConnectionOptions opts;
opts.resp = 3;
// Set other options...
デフォルトでは、 ConnectionOptions::respは2、つまりRESPバージョン2を使用します。これまでのところ、バージョン2と3のみがサポートされており、 ConnectionOptions::resp他の数字にreSで設定すると、動作は未定義です。
注：この新しいプロトコルを使用するには、最新のHiredisをインストールする必要があります（Hiredis-V1.0.2でさえRESP3サポートにバグがあります）。
プール内の接続はゆっくりと作成されています。接続プールが初期化されている場合、つまりRedisのコンストラクター、 Redisサーバーに接続しません。代わりに、コマンドを送信しようとするときにのみサーバーに接続します。このようにして、不必要な接続を回避できます。したがって、プールサイズが5の場合、最大接続接続の数が3の場合、プールには3つの接続しかありません。
Redisオブジェクトがサーバーに正常に接続するかどうかを確認する必要はありません。 Redis Redisサーバーへの接続を作成できない場合、またはいつか接続が壊れている場合、 Redisでコマンドを送信しようとすると、タイプErrorの例外がスローされます。例外を取得しても、つまり接続が壊れている場合でも、新しいRedisオブジェクトを作成する必要はありません。 Redisオブジェクトを再利用してコマンドを送信すると、 Redisオブジェクトは自動的にサーバーに再接続しようとします。正常に再接続すると、コマンドをサーバーに送信します。それ以外の場合、それは再び例外をスローします。
例外に関する詳細については、例外セクションを参照してください。
Redis Serverへの新しい接続を作成するため、 Redisオブジェクトを作成することは安くはありません。したがって、 Redisオブジェクトを可能な限り再利用する方が良いでしょう。また、Multi-Thread環境でRedisのメンバー関数を呼び出すことも安全であり、複数のスレッドでRedisオブジェクトを共有できます。
// 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にはTLSサポートもあります。ただし、この機能を使用するには、 HiredisとRedis-Plus-Plusを構築するときに有効にする必要があります。
注：これまでのところ、TLS機能はWindowsプラットフォームでテストされていません。将来修正します。
TLSサポートを使用してHiredisを構築する場合、バージョンv1.0.0または後者のHiredisをダウンロードし、 USE_SSL=1フラグを指定する必要があります。
make PREFIX=/non/default/path USE_SSL=1
make PREFIX=/non/default/path USE_SSL=1 install次に、 -DREDIS_PLUS_PLUS_USE_TLS=ON option：を指定することにより、 Redis-Plus-Plusを作成してTLSサポートを有効にすることができます。
cmake -DREDIS_PLUS_PLUS_USE_TLS=ON ..TLSサポートを使用してRedisに接続するには、次の接続オプションを指定する必要があります。
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 tls.certとtls.keyはオプションですが、そのうちの1つを指定する場合は、もう1つを指定する必要があります。 tls.cacertを指定する代わりに、証明書が保存されているディレクトリにtls.cacertdirを指定することもできます。
これらのオプションは、 redis-cliのTLS関連のコマンドライン引数と同じであるため、 redis-cli --helpを実行してこれらのオプションの詳細な説明を取得することもできます。
次に、このConnectionOptionsを使用してRedisオブジェクトを作成して、TLSサポートを使用してRedisサーバーに接続できます。
注：アプリケーションコードを構築するときは、 libhiredis.a 、 libhiredis_ssl.a 、 libredis++.a （または対応する共有ライブラリ）、 -lsslおよび-lcryptoにリンクする必要があります。
デフォルトでは、 Redis-Plus-PlusはOpenSSLライブラリを自動的に初期化し、IEはSSL_library_initを呼び出し、必要に応じてロックを初期化します。ただし、アプリケーションコードはすでにOpenSSLライブラリを初期化する場合があります。この場合、 tls::disable_auto_init()に電話して初期化を無効にできます。この関数を1回だけ呼び出し、他のRedis-Plusプラス操作の前に呼び出す必要があります。それ以外の場合、動作は未定義です。
Hiredis v1.1.0以来、証明書の確認のスキップをサポートしています。この機能をRedis-Plus-Plusで使用する場合は、この問題を例として確認できます。
Redisオブジェクトを介してRedisコマンドを送信できます。 Redisは、Redisコマンドごとに1つ以上の（過負荷）メソッドがあります。このメソッドは、対応するコマンドと同じ（低い）名前です。たとえば、 DEL key [key ...]コマンドに3つのオーバーロード方法があります。
// 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);入力パラメーターを使用すると、これらのメソッドはRedisプロトコルに基づいてRedisコマンドを構築し、Redisサーバーにコマンドを送信します。次に、応答を同期して受信し、解析し、発信者に戻ります。
これらのメソッドのパラメーターと戻り値を詳しく見てみましょう。
これらのメソッドのほとんどは、対応するコマンドと同じパラメーターを持っています。以下は、パラメータータイプのリストです。
| パラメータータイプ | 説明 | 例 | 注記 |
|---|---|---|---|
| StringView | 文字列タイプのパラメーター。通常、キー、値、メンバー名、フィールド名などに使用されます | bool redis :: hset（const stringview＆key、const stringview＆field、const stringview＆val） | StringViewの詳細については、StringViewセクションを参照してください |
| 長い | 整数タイプのパラメーター。通常、インデックス（リストコマンドなど）または整数に使用されます | void ltrim（const stringview＆key、long long start、long long stop） ロングロングデクビー（const stringview＆key、long long decrement） | |
| ダブル | フローティングポイントタイプのパラメーター。通常、スコア（ソートされたセットコマンドなど）またはフローティングポイントタイプの数に使用されます | double incrbyfloat（const stringview＆key、double increment） | |
| STD :: Chrono ::期間 std :: chrono :: time_point | 時間関連パラメーター | bool expire（const stringview＆key、const std :: chrono ::秒＆タイムアウト） bool expireat（const stringview＆key、const std :: chrono :: time_point <std :: chrono :: system_clock、std :: chrono :: seconds>＆tp） | |
| std :: pair <stringview、stringview> | Redis Hashの（フィールド、値）ペアに使用されます | bool hset（const stringview＆key、const std :: pair <stringview、stringview>＆item） | |
| std :: pair <double、double> | Redis Geo（経度、緯度）ペアに使用されます | OptionAllongLong Georadius（const StringView＆Key、const std :: pair <double、double>＆location、double radius、geounit unit、const stringview＆destination、bool store_dist、long long count） | |
| イテレーターのペア | 一対の反復器を使用して、さまざまな入力を指定して、STLコンテナ内のデータをこれらのメソッドに渡すことができるようにします。 | テンプレート<typename input> 長いdel（最初に入力、最後に入力） | 空の範囲の場合、例外を投げます、すなわちfirst == last |
| std :: hirtingizer_list <t> | 初期化リストを使用して、入力のバッチを指定する | テンプレート<typename t> long long del（std :: initializer_list <t> il） | |
| いくつかのオプション | いくつかのコマンドのオプション | updateType 、テンプレート<typename t> class boundedInterval | 詳細については、command_options.hを参照してください |
std :: string_viewは、読み取り専用の文字列パラメータータイプに適しています。ただし、 std::string_viewはC ++ 17標準でのみ導入されていたため、 -std=c++11でRedis -Plus -Plusを構築する場合（つまり、 -DREDIS_PLUS_PLUS_CXX_STANDARD=11 Cmakeコマンドで指定します）または-std=c++14のstd::string_viewの単純な実装、 StringViewの単純な実装、 -std=c++17標準（つまり、デフォルトの動作）を使用してredis-plus-plus std::string_view構築できます。 StringView実装は、 std::string_viewにエイリアスすることにより無視されます。これは、 redis-plus-plusライブラリ内で行われます： using StringView = std::string_view 。
std::string and c-style stringからStringViewへの変換があるため、 StringViewパラメーターが必要なメソッドにstd::stringまたはc-style stringを渡すことができます。
// bool Redis::hset(const StringView &key, const StringView &field, const StringView &val)
// Pass c-style string to StringView.
redis.hset( " key " , " field " , " value " );
// Pass std::string to StringView.
std::string key = " key " ;
std::string field = " field " ;
std::string val = " val " ;
redis.hset(key, field, val);
// Mix std::string and c-style string.
redis.hset(key, field, " value " );Redisプロトコルは5種類の返信を定義します。
long long保持するのに十分な大きさ。また、これらの応答はヌルかもしれません。たとえば、存在しないキーの値GETうとすると、RedisはNull Bulk Stringの返信を返します。
上で述べたように、回答はこれらの方法の返された値に解析されます。以下は、返品タイプのリストです。
| 返品タイプ | 説明 | 例 | 注記 |
|---|---|---|---|
| 空所 | 常に「OK」の文字列を返す必要があるステータス返信 | 名前を変更してください | |
| std :: string | 常に「OK」を返すとは限らず、バルク文字列返信 | ping 、情報 | |
| ブール | 常に0または1を返す整数の返信 | 期限切れ、 hset | ブールリターン値の意味については、ブールリターン値セクションを参照してください |
| 長い | 整数は、常に0または1を返すとは限らないという回答があります | del 、 append | |
| ダブル | 二重を表すバルク文字列応答 | inclbyfloat 、 zincrby | |
| std ::ペア | 正確に2つの要素を使用した配列返信。戻り値は常に2つの要素の配列であるため、2つの要素をstd::pairの最初と2番目の要素として返します | blpop | |
| std ::タプル | 固定長で、2つ以上の要素を持つ配列応答があります。返された配列の長さが固定されているため、配列をstd::tupleとして返します | bzpopmax | |
| 出力イテレータ | 非固定/動的長の一般的な配列応答。 STLのようなインターフェイスを使用して、この種のアレイ応答を返して、STLコンテナに戻り値を簡単に挿入できるようにします | mget 、 lrange | また、出力Iteratorの種類がコマンドで送信するオプションを決定する場合があります。詳細については、例のセクションを参照してください |
| オプション<t> | nullである可能性のあるタイプTの返信について | get 、 lpop 、 blpop 、 bzpopmax | Optional<T>の詳細については、オプションのセクションを参照してください |
| バリアント<args ...> | サービスのために、それはサービスの異なるタイプのものかもしれません | メモリ統計 | 注：これまでのところ、このタイプは、C ++ 17標準でRedis-Plus-Plusをコンパイルするときにのみサポートされています。これは通常、汎用コマンドインターフェイスで使用されます。 Variant<Args...>の詳細については、バリアントセクションを参照してください |
| STLコンテナ | 一般的な配列返信 | config get | 出力イテレータとSTLコンテナの両方が配列の応答に使用されます。違いは、 STLコンテナが通常、汎用コマンドインターフェイスで使用されることです。たとえば、STLコンテナセクションを参照してください |
いくつかの方法のリターンタイプ、例： EXPIRE 、 HSET 、 bool 。メソッドがfalseを返す場合、 Redis Redisサーバーにコマンドを送信できなかったという意味ではありません。代わりに、Redisサーバーが整数応答を返し、返信の値は0です。したがって、メソッドがtrueを返す場合、Redisサーバーが整数応答を返し、返信の値は1です。 0と1略で、Redisコマンドマニュアルを確認できます。
たとえば、redisサーバーにEXPIREコマンドを送信すると、タイムアウトが設定されている場合は1返し、キーが存在しない場合に0返します。したがって、タイムアウトが設定されている場合、 Redis::expire trueを返し、キーが存在しない場合、 Redis::expire false返します。
したがって、リターン値を使用して、コマンドがRedisサーバーに正常に送信されたかどうかを確認しないでください。代わりに、 Redisサーバーにコマンドを送信できなかった場合、タイプErrorの例外がスローされます。例外に関する詳細については、例外セクションを参照してください。
std :: optionalは、Redisがnull返信を返す可能性がある場合、返品タイプに適したオプションです。ただし、 std::optional C ++ 17 Standardで導入され、 -std=c++11標準でRedis -Plus -Plusを構築する場合（つまり、 -DREDIS_PLUS_PLUS_CXX_STANDARD=11 Cmakeコマンドで指定します）、独自のシンプルなバージョン、すなわちtemplate Optional<T>を実装します。代わりに、 -std=c++17標準（つまりデフォルトの動作）でredis-plus-plusを構築する場合、 std::optionalを使用でき、エイリアスがあります。 template <typename T> using Optional = std::optional<T> 。
get and mgetコマンドを取ります。たとえば
// 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.
}
}また、一般的に使用されるOptional<T>のTypedefもいくつかあります。
using OptionalString = Optional<std::string>;
using OptionalLongLong = Optional< long long >;
using OptionalDouble = Optional< double >;
using OptionalStringPair = Optional<std::pair<std::string, std::string>>;std :: variantは、返信が異なる場合がある場合は、返品タイプに適したオプションです。たとえば、 MEMORY STATSコマンドは配列返信を返します。これは、実際には構成のキー価値ペアのマップです。
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 "
...ただし、ご覧のとおり、結果の値部分は、長い型（key： peak.allocated ）、double（key： dataset.percentage ）、またはマップ（key： db.0 ）である可能性があります。したがって、結果std::unordered_map<std::string, long long>またはstd::unordered_map<std::string, double>に単純に解析することはできません。回避策は、結果をtupleに解析することですが、このタプルソリューションは醜く、エラーが発生しやすいです。詳細については、この問題を確認してください。
この場合、C ++ 17標準でRedis-Plus-Plusを構築する場合、 std::variantのtypedefであるVariantは非常に役立ちます。結果をstd::unordered_map<std::string, Variant<double, long long, std::unordered_map<std::string, long long>>>に解析できます。
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 " ); Variantサポートにはいくつかの制限があります。
Variantのタイプの引数は、アイテムを重複させることはできません。たとえば、 Variant<double, long long, double>機能しません。double std::stringの前に配置する必要があります。実際、 double応答は文字列応答であり、バリアントを解析するときに、左から右へのタイプの引数で指定された最初の一致したタイプに応答を解析しようとします。したがって、 std::stringの後にdoubleが配置されている場合、つまり、 std::stringの右側にある場合、返信は常にstd::stringに解析されます。また、一般的なコマンドインターフェイスのその他の例については、汎用コマンドセクションを確認してください。
一般的なコマンドインターフェイスを使用する場合、出力イテレータへの応答を解析する代わりに、STLコンテナに解析することもできます。
auto r = Redis( " tcp://127.0.0.1 " );
auto v = r.command<std::unordered_map<std::string, std::string>>( " config " , " get " , " * " );また、一般的なコマンドインターフェイスのその他の例については、汎用コマンドセクションを確認してください。
Redisサーバーにコマンドを送信する方法についての例をいくつか見てみましょう。
// ***** 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 ;
}
}時々、出力Iteratorのタイプがコマンドで送信するオプションを決定します。
// 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));DoxygenスタイルのAPI参照と例については、Redis.hを参照してください。他の例のテストをご覧ください。
Redis 、エラーの返信を受信した場合、または何か悪いことが発生した場合、例外をスローします。たとえば、サーバーへの接続を作成できない場合、またはサーバーへの接続が壊れています。 Errorクラスから派生したすべての例外。詳細については、errors.hを参照してください。
Error ：一般的なエラー。 std::exceptionから派生しており、他の例外の基本クラスでもあります。IoError ：接続にはIOエラーがあります。TimeoutError ：読み取りまたは書き込み操作がタイムアウトしました。 IoErrorの派生クラスです。ClosedError ：Redisサーバーは接続を閉じました。ProtoError ：コマンドまたは返信は無効であり、Redisプロトコルで処理することはできません。OomError ： Hiredis Libraryには、メモリ外のエラーが発生しました。ReplyError ：Redis Serverはエラー返信を返しましredis::lrange 。WatchError ：監視キーが変更されました。詳細については、視聴セクションを参照してください。注： nullの返信は例外としてはとられていません。たとえば、存在しないキーGETうとすると、 Null Bulk Stringの返信が表示されます。例外をスローする代わりに、 null応答をnull Optional<T>オブジェクトとして返します。また、オプションのセクションを参照してください。
通常、例外が発生した場合、 Redisオブジェクトを作成する必要はありません。それは例外で安全であり、 Redisオブジェクトを再利用できます。 Redisサーバーへの接続が壊れていても、たとえばIoErrorなどの例外をスローしていても。次にRedisオブジェクトを使用してコマンドを送信するとき、Redisサーバーに自動的に再接続しようとします。このルールは、 RedisClusterにも適用されます。ただし、 Pipeline 、 Transcation 、 Subscriber例外をスローする場合、オブジェクトを破壊し、新しいオブジェクトを作成する必要があります。詳細については、対応するドキュメントを参照してください。
以下は、これらの例外をキャッチする方法の例です。
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
}Redisコマンドが多すぎるので、それらのすべてを実装していません。ただし、一般的なRedis::commandメソッドを使用して、redisにコマンドを送信できます。他のクライアントライブラリとは異なり、 Redis::commandフォーマット文字列を使用してコマンド引数をコマンド文字列に結合しません。代わりに、 Redis::commandのパラメーターとして、 StringViewタイプまたは算術タイプのコマンド引数を直接渡すことができます。フォーマット文字列を使用しない理由から、このディスカッションをご覧ください。
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));注：いくつかのRedisコマンドの名前は、クライアントSetNameなどの2つの文字列で構成されています。この場合、 Redis::commandの2つの引数として、これら2つの文字列を渡す必要があります。
// 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");コメントで述べたように、 SETコマンドは常にvoidを返すとは限りません。 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 installThe 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.
注記：
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 installThe 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.
注記：
# 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.
