创建 redis 扩展模块 module

创建日期: 2024-10-18 12:35 | 作者: 风波 | 浏览次数: 19 | 分类: Redis

两个比较有名的 redis 模块

redis 模块文档：https://redis.io/docs/latest/develop/reference/modules/

1. 模块代码

文件 hello.cc

#include "redismodule.h"
#include <stdlib.h>

int HelloworldRand_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
    RedisModule_ReplyWithLongLong(ctx,rand());
    return REDISMODULE_OK;
}


const char * modulename = "helloworld";
const char * command = "helloworld.rand";

int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
    if (RedisModule_Init(ctx, modulename, 1, REDISMODULE_APIVER_1)
        == REDISMODULE_ERR) return REDISMODULE_ERR;

    if (RedisModule_CreateCommand(ctx, command,
        HelloworldRand_RedisCommand, "fast random",
        0, 0, 0) == REDISMODULE_ERR)
        return REDISMODULE_ERR;

    return REDISMODULE_OK;
}

2. CMakeLists.txt

PROJECT (redis-module)

INCLUDE_DIRECTORIES (
    ${CMAKE_CURRENT_SOURCE_DIR}/../redis-7.4.1/src # 目的是引用 "redismodule.h"
    )

LINK_DIRECTORIES (
    ${CMAKE_CURRENT_SOURCE_DIR}/target
    )

ADD_LIBRARY (htmlparser_shared SHARED src/hello.cc)
SET_TARGET_PROPERTIES(htmlparser_shared PROPERTIES OUTPUT_NAME "hello") # 输出文件名 libhello.so
SET_TARGET_PROPERTIES(htmlparser_shared PROPERTIES CLEAN_DIRECT_OUTPUT 1)

3. 加载模块

修改文件 redis.conf，增加一行

loadmodule /root/workspace/hello/target/libhello.so

或者在执行命令的时候增加参数 --loadmodule

./src/redis-server --loadmodule /root/workspace/hello/target/libhello.so

4. 使用 redis-cli 查看加载的模块 动态加载/卸载模块

  1. 加载模块
MODULE LOAD /path/to/mymodule.so
  1. 查看已经加载的模块列表
> MODULE LIST
  1. 卸载模块
MODULE UNLOAD mymodule

5. 模块中可以使用的 API

int RedisModule_Init(RedisModuleCtx *ctx, const char *modulename,
                     int module_version, int api_version);

int RedisModule_CreateCommand(RedisModuleCtx *ctx, const char *name,
                              RedisModuleCmdFunc cmdfunc, const char *strflags,
                              int firstkey, int lastkey, int keystep);

int mycommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc);

int RedisModule_ReplyWithLongLong(RedisModuleCtx *ctx, long long integer);

int RedisModule_OnUnload(RedisModuleCtx *ctx);

In most cases, there is no need for special cleanup. When a module is unloaded, Redis will automatically unregister commands and unsubscribe from notifications. However in the case where a module contains some persistent memory or configuration, a module may include an optional RedisModule_OnUnload function. If a module provides this function, it will be invoked during the module unload process. The following is the function prototype: The OnUnload function may prevent module unloading by returning REDISMODULE_ERR. Otherwise, REDISMODULE_OK should be returned.

RedisModuleString *mystr = RedisModule_CreateStringFromLongLong(ctx,10);
# --
long long myval;
if (RedisModule_StringToLongLong(ctx,argv[1],&myval) == REDISMODULE_OK) {
    /* Do something with 'myval' */
}

RedisModuleCallReply *reply;
reply = RedisModule_Call(ctx,"INCRBY","sc",argv[1],"10");
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