redis 删除超时key

        该功能主要通过expireIfNeeded 这个函数来实现的，redis对于需要设置超时的key,放到了单独的一个hash中，所以只要检测这个超时hash就可以了。

//检查是否超时，超时了那么就删除int expireIfNeeded(redisDb *db, robj *key) {    time_t when = getExpire(db,key);    //该key没有设置超时    if (when < 0) return 0; /* No expire for this key */    //正在载入    /* Don't expire anything while loading. It will be done later. */    if (server.loading) return 0;    //如果是slave, 它不需要直接进行删除的，它的删除有master来控制的，但是它需要调用者一个返回直：是不是超时.    /* If we are running in the context of a slave, 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) {        return time(NULL) > when;    }    //存在但未超时    /* Return when this key has not expired */    if (time(NULL) <= when) return 0;    //删除并通知文件和slave    /* Delete the key */    server.stat_expiredkeys++;    propagateExpire(db,key);    return dbDelete(db,key);}

对不同的情况，做不同的处理，我们再来看看propageteExpire函数

void propagateExpire(redisDb *db, robj *key) {    robj *argv[2];    argv[0] = createStringObject("DEL",3);    argv[1] = key;    incrRefCount(key);    //只有在appendonly开启的时候，才进行操作    if (server.appendonly)        feedAppendOnlyFile(server.delCommand,db->id,argv,2);    if (listLength(server.slaves))        replicationFeedSlaves(server.slaves,db->id,argv,2);    decrRefCount(argv[0]);    decrRefCount(argv[1]);}

如果开启了appendonly,那么从append文件中进行删除。 

如果存在slaves，那么从slave中进行删除