Redis过期数据的删除策略详解

# 缓存时间过期命令，参考如下
EXPIRE key seconds [ NX | XX | GT | LT] 

redis> SET mykey "Hello"
"OK"
redis> EXPIRE mykey 10
(integer) 1
redis> TTL mykey
(integer) 10
redis> SET mykey "Hello World"
"OK"
redis> TTL mykey
(integer) -1
redis> EXPIRE mykey 10 XX
(integer) 0
redis> TTL mykey
(integer) -1
redis> EXPIRE mykey 10 NX
(integer) 1
redis> TTL mykey
(integer) 10
 

int expireIfNeeded(redisDb *db, robj *key, int force_delete_expired) {
    // 对于未过期的key，直接 return 0
    if (!keyIsExpired(db,key)) return 0;	
	 /* If we are running in the context of a slave, instead of
     * evicting the expired key from the database, we return ASAP:
     * the slave key expiration is controlled by the master that will
     * send us synthesized DEL operations for expired keys.
     *
     * Still we try to return the right information to the caller,
     * that is, 0 if we think the key should be still valid, 1 if
     * we think the key is expired at this time. */
    if (server.masterhost != NULL) {
        if (server.current_client == server.master) return 0;
        if (!force_delete_expired) return 1;
    }
  /* If clients are paused, we keep the current dataset constant,
     * but return to the client what we believe is the right state. Typically,
     * at the end of the pause we will properly expire the key OR we will
     * have failed over and the new primary will send us the expire. */
    if (checkClientPauseTimeoutAndReturnIfPaused()) return 1;
    /* Delete the key */
    deleteExpiredKeyAndPropagate(db,key);
    return 1;
}

# 代表每1s 运行 10次
hz 10