Redis模块开发示例
2024-09-14 13:45:18
实现一个Redis module，支持两个扩展命令：
1) 可同时对hash的多个field进行incr操作；
2) incrby同时设置一个key的过期时间
在没有module之前，需要借助eval+lua实现相同的功能。有了module，不但可以实现逻辑复杂，且性能高的扩展，同时享受Redis的持久化和容灾能力。
// Redis命令扩展module
#include "redismodule.h"
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
// 带超时的INCRBY命令
// 格式：INCRBYEX KEY SECONDS INCREMENT
//
// 示例：
// ex.incrbyex k1 10 1
// ex.incrbyex k1 10 2
int incrbyex_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
// When automatic memory management is enabled:
// 1) don't need to close open keys
// 2) don't need to free replies
// 3) don't need to free RedisModuleString objects
RedisModule_AutoMemory(ctx); /* Use automatic memory management. */
if (argc != 4) return RedisModule_WrongArity(ctx);
RedisModuleKey *key = (RedisModuleKey*)RedisModule_OpenKey(ctx, argv[1],
REDISMODULE_READ|REDISMODULE_WRITE);
int type = RedisModule_KeyType(key);
if (type != REDISMODULE_KEYTYPE_STRING &&
type != REDISMODULE_KEYTYPE_EMPTY)
{
return RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
}
RedisModuleString* seconds = argv[2];
RedisModuleString* increment = argv[3];
long long ll_seconds; // 过期时长
long long ll_newval; // 新的值
if (RedisModule_StringToLongLong(seconds, &ll_seconds) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx, "ERR value is not an integer or out of range");
}
if (RedisModule_StringToLongLong(increment, &ll_newval) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx, "ERR value is not an integer or out of range");
}
size_t len;
char *s = RedisModule_StringDMA(key, &len, REDISMODULE_READ|REDISMODULE_WRITE);
if (0 == len || NULL == s || s == '\0') {
// set必须在Expire之前，否则会冲掉Expire的作用，
// 这也是else分支未用RedisModule_StringSet的原因
RedisModule_StringSet(key, increment);
RedisModule_SetExpire(key, ll_seconds*1000); // 以秒为单位，需要乘以1000
}
else {
char* endptr;
long long ll_oldval = strtoll(s, &endptr, 10); // s不一定是有效的数字，所以需要做检查
ll_newval = ll_newval + ll_oldval;
if ((errno == ERANGE && (ll_oldval == LLONG_MAX || ll_oldval == LLONG_MIN))
|| (errno != 0 && ll_oldval == 0)) {
return RedisModule_ReplyWithError(ctx, "ERR value is not an integer or out of range");
}
if (endptr == s || *endptr != '\0') {
return RedisModule_ReplyWithError(ctx, "ERR value is not an integer or out of range");
}
size_t newval_len;
RedisModuleString* newval = RedisModule_CreateStringFromLongLong(ctx, ll_newval);
const char* newval_s = RedisModule_StringPtrLen(newval, &newval_len);
if (newval_len > len)
RedisModule_StringTruncate(key, newval_len);
strncpy(s, newval_s, newval_len);
}
RedisModule_ReplicateVerbatim(ctx); // 写AOF和复制到slaves
RedisModule_ReplyWithLongLong(ctx, ll_newval);
return REDISMODULE_OK;
}
// 实现命令HMINCRBY，同时对HASH的多个field值进行增减操作
// 格式：HMINCRBY KEY FIELD1 VALUE1 FIELD2 VALUE2 FIELD3 VALUE3 ......
//
// 示例：
// hmincrby k1 f1 1 f2 2
// hmincrby k1 f5 1 f6 2 f7 3
int hmincrby_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
// When automatic memory management is enabled:
// 1) don't need to close open keys
// 2) don't need to free replies
// 3) don't need to free RedisModuleString objects
RedisModule_AutoMemory(ctx); /* Use automatic memory management. */
if (argc < 4 || argc % 2 != 0) return RedisModule_WrongArity(ctx);
RedisModuleKey *key = (RedisModuleKey*)RedisModule_OpenKey(ctx, argv[1],
REDISMODULE_READ|REDISMODULE_WRITE);
int type = RedisModule_KeyType(key);
if (type != REDISMODULE_KEYTYPE_HASH &&
type != REDISMODULE_KEYTYPE_EMPTY)
{
return RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
}
const int count = argc/2 - 1; // 键值对个数
std::vector<long long> newval_array(count); // 用来存储新值的数组
for (int i=2; i<argc; i+=2) {
RedisModuleString* field = argv[i];
RedisModuleString* incrvalue = argv[i+1];
long long ll_newvalue;
if (RedisModule_StringToLongLong(incrvalue, &ll_newvalue) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx, "ERR value is not an integer or out of range");
}
RedisModuleString *oldval;
RedisModule_HashGet(key, REDISMODULE_HASH_NONE, field, &oldval, NULL);
if (NULL == oldval) { // field不存在时
RedisModule_HashSet(key,REDISMODULE_HASH_NONE, field, incrvalue, NULL);
}
else { // field已存在时
long long ll_oldval;
if (RedisModule_StringToLongLong(oldval, &ll_oldval) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx, "ERR hash value is not an integer");
}
ll_newvalue = ll_newvalue + ll_oldval; // 累加得到新值
RedisModuleString* newval = RedisModule_CreateStringFromLongLong(ctx, ll_newvalue);
RedisModule_HashSet(key,REDISMODULE_HASH_NONE, field, newval, NULL);
}
newval_array[i] = ll_newvalue;
}
RedisModule_ReplicateVerbatim(ctx); // 写AOF和复制到slaves
RedisModule_ReplyWithArray(ctx, count); // 返回数组类型的Reply
for (std::vector<long long>::size_type i=0; i<newval_array.size(); ++i)
RedisModule_ReplyWithLongLong(ctx, newval_array[i]);
return REDISMODULE_OK;
}
extern "C"
int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
if (RedisModule_Init(ctx, "command_extension", 1, REDISMODULE_APIVER_1)
== REDISMODULE_ERR) return REDISMODULE_ERR;
/* Log the list of parameters passing loading the module. */
for (int j=0; j<argc; ++j) {
const char *s = RedisModule_StringPtrLen(argv[j], NULL);
printf("Module loaded with ARGV[%d] = %s\n", j, s);
}
if (RedisModule_CreateCommand(ctx, "ex.incrbyex",
incrbyex_RedisCommand,"write", 1, 1, 1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx, "ex.hmincrby",
hmincrby_RedisCommand,"write", 1, 1, 1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
return REDISMODULE_OK;
}
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