We’ve been having some upload issues on our Discourse instance recently: most of the time, if you upload an image it will never finish. Occasionally it will, but only after a lengthy wait.
After doing some investigation, it seems to be down to a problem with MessageBus. If I subscribe to the
/uploads/composer channel on the server, I’ll get a message containing a working url almost as soon as I’ve clicked upload. The message will usually never get to the client.
This doesn’t just affect uploads, but seemingly all MessageBus channels. Post edits won’t appear before a refresh, and if I subscribe to a test channel I create on the client and push messages to it from the server they won’t arrive.
The one scenario where messages will arrive (more often than not) is if I have two discourse tabs open - when I switch to the second tab, the message will arrive in the first tab.
This is definitely a misconfiguration we have on discourse.mozilla.org - as uploads are working fine here - but I’m not sure what it could be. We only put static assets behind a CDN, and dynamic content is behind ELB and HAProxy - but we’ve changed none of that since we’ve started seeing issues.
Anyone got an idea what could be going on here? I’m pretty stumped…