Can't Pub/Sub On Same Client

[daneren2005]

It appears that pub sub is not really async. After trying to figure out why I wasn't receiving commands on another client, I finally tried commenting out $client->subscribe($channel); and all of a sudden the publish commands were going through.

With a client subscribe the following code never logged the publish complete message:

$this->redis->publish($this->channel, json_encode($msg))->then(function($return) {
    $this->debug('Publish received ' . $return);
});

[clue]

This is a limitation of Redis and unfortunately there's nothing this library (or any other library for that matter) can do about this. See also http://redis.io/topics/pubsub and http://redis.io/commands/subscribe.

You can easily reproduce this by connecting to your Redis instance via telnet:

$ telnet localhost 6379
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
subscribe a
*3
$9
subscribe
$1
a
:1
publish a b
-ERR only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT allowed in this context

As you've already figured out, the correct workaround is to use two independent connections.

I hope this helps 👍

[daneren2005]

Oh well that stinks. I was hoping because it async it meant you could listen for replies to the subscribe and publish on the same channel. That does make sense that it is a Redis thing which you can't work around.