/* Helper function for the redisAsyncCommand* family of functions. Writes a
* formatted command to the output buffer and registers the provided callback
* function with the context. */
static int __redisAsyncCommand(redisAsyncContext *ac, redisCallbackFn *fn, void *privdata, char *cmd, size_t len) {
redisContext *c = &(ac->c);
redisCallback cb;
int pvariant, hasnext;
char *cstr, *astr;
size_t clen, alen;
char *p;
sds sname;
/* Don't accept new commands when the connection is about to be closed. */
if (c->flags & (REDIS_DISCONNECTING | REDIS_FREEING)) return REDIS_ERR;
/* Setup callback */
cb.fn = fn;
cb.privdata = privdata;
/* Find out which command will be appended. */
p = nextArgument(cmd,&cstr,&clen);
assert(p != NULL);
hasnext = (p[0] == '$');
pvariant = (tolower(cstr[0]) == 'p') ? 1 : 0;
cstr += pvariant;
clen -= pvariant;
if (hasnext && strncasecmp(cstr,"subscribe\r\n",11) == 0) {
c->flags |= REDIS_SUBSCRIBED;
/* Add every channel/pattern to the list of subscription callbacks. */
while ((p = nextArgument(p,&astr,&alen)) != NULL) {
sname = sdsnewlen(astr,alen);
if (pvariant)
dictReplace(ac->sub.patterns,sname,&cb);
else
dictReplace(ac->sub.channels,sname,&cb);
}
} else if (strncasecmp(cstr,"unsubscribe\r\n",13) == 0) {
/* It is only useful to call (P)UNSUBSCRIBE when the context is
* subscribed to one or more channels or patterns. */
if (!(c->flags & REDIS_SUBSCRIBED)) return REDIS_ERR;
/* (P)UNSUBSCRIBE does not have its own response: every channel or
* pattern that is unsubscribed will receive a message. This means we
* should not append a callback function for this command. */
} else {
if (c->flags & REDIS_SUBSCRIBED)
/* This will likely result in an error reply, but it needs to be
* received and passed to the callback. */
__redisPushCallback(&ac->sub.invalid,&cb);
else
__redisPushCallback(&ac->replies,&cb);
}
__redisAppendCommand(c,cmd,len);
/* Always schedule a write when the write buffer is non-empty */
if (ac->ev.addWrite) ac->ev.addWrite(ac->ev.data);
return REDIS_OK;
}
void redisProcessCallbacks(redisAsyncContext *ac) {
redisContext *c = &(ac->c);
redisCallback cb;
void *reply = NULL;
int status;
while((status = redisGetReply(c,&reply)) == REDIS_OK) {
// 回复内容为空
if (reply == NULL) {
// REDIS_DISCONNECTING 表示连接断开的时候遇到了错误，如果此时
// 写缓冲区为空，会再次尝试断开。之后的回调函数都得不到执行
// 的机会
/* When the connection is being disconnected and there are
* no more replies, this is the cue to really disconnect. */
if (c->flags & REDIS_DISCONNECTING && sdslen(c->obuf) == 0) {
__redisAsyncDisconnect(ac);
return;
}
// 监视模式下
/* If monitor mode, repush callback */
if(c->flags & REDIS_MONITORING) {
__redisPushCallback(&ac->replies,&cb);
}
/* When the connection is not being disconnected, simply stop
* trying to get replies and wait for the next loop tick. */
break;
}
/* Even if the context is subscribed, pending regular callbacks will
* get a reply before pub/sub messages arrive. */
// 获取回调函数 redisCallback
if (__redisShiftCallback(&ac->replies,&cb) != REDIS_OK) {
/*
* A spontaneous reply in a not-subscribed context can be the error
* reply that is sent when a new connection exceeds the maximum
* number of allowed connections on the server side.
*
* This is seen as an error instead of a regular reply because the
* server closes the connection after sending it.
*
* To prevent the error from being overwritten by an EOF error the
* connection is closed here. See issue #43.
*
* Another possibility is that the server is loading its dataset.
* In this case we also want to close the connection, and have the
* user wait until the server is ready to take our request.
*/
if (((redisReply*)reply)->type == REDIS_REPLY_ERROR) {
c->err = REDIS_ERR_OTHER;
snprintf(c->errstr,sizeof(c->errstr),"%s",((redisReply*)reply)->str);
__redisAsyncDisconnect(ac);
return;
}
/* No more regular callbacks and no errors, the context *must* be subscribed or monitoring. */
assert((c->flags & REDIS_SUBSCRIBED || c->flags & REDIS_MONITORING));
if(c->flags & REDIS_SUBSCRIBED)
__redisGetSubscribeCallback(ac,reply,&cb);
}
// 执行回调函数
if (cb.fn != NULL) {
__redisRunCallback(ac,&cb,reply);
c->reader->fn->freeObject(reply);
// 可能是之前遇到了不可修复的错误，被标记了 REDIS_FREEING。
// 倘若是在 callback 里面遇到的错误，redis 不能立即释放连接，
// 因为可能需要返回一些数据给客户端。因此 redis 选择在 callback
// 执行过后，才释放（关闭）连接。这个方法好酷。
/* Proceed with free'ing when redisAsyncFree() was called. */
if (c->flags & REDIS_FREEING) {
__redisAsyncFree(ac);
return;
}
// 没有设置回调函数，直接释放收到的数据
} else {
/* No callback for this reply. This can either be a NULL callback,
* or there were no callbacks to begin with. Either way, don't
* abort with an error, but simply ignore it because the client
* doesn't know what the server will spit out over the wire. */
c->reader->fn->freeObject(reply);
}
}
// 出错了，则直接关闭
/* Disconnect when there was an error reading the reply */
if (status != REDIS_OK)
__redisAsyncDisconnect(ac);
}
/* lig: monitor callback */
static int __redisGetMonitorCallback(redisAsyncContext *ac, redisCallback *dstcb) {
__redisShiftCallback(&ac->mon.invalid,dstcb);
__redisPushCallback(&ac->mon.invalid,dstcb);
return REDIS_OK;
}
