A topic doesn't open with recent upgrade due to a plugin

[k4rtik (Kartik)]

Continuing the discussion from Https://docs.discourse.org/ spinning:

@k4rtik

one of the topics on my self-hosted Discourse instance is just spinning on v77 (observed yesterday on Linux and just now on macOS). […] that topic loaded perfectly fine on v76 before I updated. This one just keeps spinning and has not even gotten around to printing the error on the console. The only peculiar thing about this page is that it has had dozens of wiki edits. Rest of my site seems to work fine.

I do not see anything captured in /logs or the Chrome console.

If there is a way I can provide more info to help debug this issue, please let me know.

[jomaxro (Joshua Rosenfeld)]

Thanks for splitting this off. I take it other topics load without issue, and it’s just that spins, correct?

[k4rtik (Kartik)]

Out of the dozen or so topics I have tried opening since I first noticed the issue yesterday, this is the only one I am aware of that spins.

[jomaxro (Joshua Rosenfeld)]

Does the topic load in safe mode? How to use Discourse Safe Mode

[k4rtik (Kartik)]

Yes, thanks for introducing me to the safe-mode. It works in safe mode.

I suspected that the theme component DiscoTOC that I use on that topic might be the cause, but disabling that didn’t help. Only other useful piece of info is that the tab starts using 100% CPU so Chrome offers to kill it after a while (if I kill it can leave behind a service worker still consuming CPU, that needs to be manually killed too).

EDIT: I tried playing with options available in safe mode and it looks like one of the official plugins might be causing this. As I can reproduce with disabling unofficial plugins and theme options. But cannot reproduce (ie, loads correctly) after disabling all plugins.

Here’s the list of plugins I have:

[jomaxro (Joshua Rosenfeld)]

Very strange, we run all the official plugins you have on various sites we host, and haven’t heard other reports. The next step would be to disable all plugins (comment them out in your app.yml) and rebuild your site. Confirm you can load the topic. Then, add back in one plugin and rebuild. Test again. Repeat this until the topic breaks. That should tell us which plugin is the suspect here.

Note that rebuilding your site will result in short downtime, so you may wish to do this outside of your forums busy time, and/or post a note on the site warning your users.

[k4rtik (Kartik)]

I just upgraded to Chrome 77.0.3865.90 from whatever minor version of v77 I was on when I upgraded from v76 and the problem seems to have gone away. It was probably a browser bug in the initial v77 release (it also broke WordPress).