1266289 - Figure out why Discourse is so slow

Status: RESOLVED FIXED

(Infrastructure & Operations :: Community IT: Discourse, task)

Description

[Tanner Filip [:tanner]]

It takes several seconds to load the main Discourse forum, which seems strangely slow.

Comment 1

[Stephen Donner [:stephend] Not actively reading bugmail]

(In reply to Tanner Filip [:tanner] from comment #0)
> It takes several seconds to load the main Discourse forum, which seems
> strangely slow.

Yeah, yikes: http://www.webpagetest.org/result/160421_5R_1RWA/1/details/#request14

Comment 2

[Tanner Filip [:tanner]]

Aha, that makes sense. Not long ago we re-enabled the "Long polling" setting, because we couldn't remember why it was disabled. Just disabled it again and it *seems* to be loading faster. Still want to investigate why this causes problems if it's the issue

Comment 3

[Stephen Donner [:stephend] Not actively reading bugmail]

(In reply to Tanner Filip [:tanner] from comment #2)
> Aha, that makes sense. Not long ago we re-enabled the "Long polling"
> setting, because we couldn't remember why it was disabled. Just disabled it
> again and it *seems* to be loading faster. Still want to investigate why
> this causes problems if it's the issue

Still takes around 30 seconds over a high-speed connection :-(

http://www.webpagetest.org/result/160422_T1_1CWM/

Comment 4

[Tanner Filip [:tanner]]

There are a lot of huge js files, one is over 1MB and several others over 300kB.

Comment 5

[Axel Hecht [:Pike]]

The initial page load takes 30+ seconds for me, the js afterwards is just a few seconds then. According to network panel in devtools.

Comment 6

[Axel Hecht [:Pike]]

Note, this is just the main page, the other pages load OK-ish.

Comment 7

[Leo McArdle [:leo]]

Attachment: Performance comparison between our own Discourse instance and Discourse Meta

I used Firefox dev tools to do a performance comparison between our own discourse front page [1] and the Discourse Meta categories page [2] (since that's the page we use as our front page).

The comparison is pretty shocking, we're over 25s slower than them. The biggest discrepancy is the time it takes to complete the xhr requests, which I'm pretty sure is how the content of the page is loaded. This would imply that either our server or database is slow as hell. Either way, we need to be throwing more server resources at Discourse to speed it up.

[1] https://discourse.mozilla-community.org/
[2] https://meta.discourse.org/categories

Comment 8

[Tanner Filip [:tanner]]

Attachment: Stats from the Discourse autoscaling group and RDS server

Well, I'm going to take a guess that the RDS server is at least part of the bottleneck. We need to migrate to a new one sooner rather than later.

Comment 9

[Tanner Filip [:tanner]]

Discourse was moved to the Mesos cluster a few months ago, and with that came a DB upgrade. This seems to be fixed.