Floccus sometimes hangs parts of Firefox UI

Describe the bug

Sometimes, when Floccus shows blue <-> on it’s icon to indicate it is syncing, firefox will behave strangely with parts of UI “hanged”. Eg. when I try to click on icon of some extension (like floccus or any other: foxyproxy, textarea cache, uBlock origin) it will not open that extension window, but will instead just show a white triangle below extension icon - the triangle that normally expands to extension window). I can click on other existing tabs, and even open a new tab, but I cannot open any real URL in that new tabs - it just stands there. Firefox menus work though, as does about:Config internal URL.

First time I closed Firefox to recover, but second time it seems to recover by itself after several minutes (maybe dozen?)

To Reproduce

Not quite sure. It happened twice so far today, but I’ve been unable to reproduce it at will. Seems to happen only while floccus shows it is syncing. I have 3 syncs enabled to same nextcloud account but different remote directories: Bookmarks Toolbar, Bookmarks menu, sync tabs.

Expected behavior

UI continuing to work normally while Floccus is syncing.

Screenshots

Example hang - as I see it does not open any content for github URL, also the white triangle is shown as I try to open floccus extension window but it won’t open it:

Desktop

• OS: Debian Buster GNU/Linux
• Browser: Firefox
• Browser Version: 78.12.0esr (64-bit)
• Floccus version: 4.7.0
• Floccus sync method: Nextcloud bookmarks

Server

• OS: Debian Buster GNU/Linux
• Nextcloud version: 20.0.11
• Bookmarks app version: 4.4.0

Debug log

It is often useful to provide a debug log file along with the issue. You can obtain a debug log of the most recent sync runs by clicking ‘Debug log’ in the bottom right corner of the floccus panel in your browser.

Note: As your debug log usually contains large parts of your bookmark data, instead of attaching it publicly to the issue here, I recommend uploading it privately at the following URL https://cloud.marcelklehr.de/s/PCi3iLWrzdMZSmw

• Debug log provided (not provided as I cannot click on floccus icon to retrieve it due to nature of the bug. Is there a way to manually retrieve the log outside of firefox?)

Additional context

I never noticed this problem in previous Floccus v4.6.4, but Sync tabs was disabled then too (because of https://github.com/floccusaddon/floccus/issues/883 and https://github.com/floccusaddon/floccus/issues/912)

Might be related or not:

• first time I synced tabs after upgrading floccus, after few dozen minutes it started closing and reopening what seems like all tabs (including tabs I’m sure I haven’t changed since initial tabs sync attempts, eg. for months). Each one was in “loading” state (usually my firefox is setup to only try loading tabs once I click on them, and not to load them all automatically on eg. restart), and since I have several hundred of tabs it slowed firefox considerably, so I went to do other things on the computer while all those tabs load.

• However some 20 minutes after I stopped watching firefox (so 40-50 minutes after a sync start), I’ve noticed general sluggishness, and was surprised to see Firefox was still syncing and has eaten all 8GB of RAM and 8GB of swap. I was soon forced to click x to close Firefox, which worked. After that I opened and synced tabs manually and after some time this bug occurred.

• After I restarted firefox and synced tabs again, it worked and said tabs are synced successfully.

• Some time after that, while it was syncing automatically (or it might have been me playing with manual sync before and sync not being completed yet, I’m not sure), floccus experienced the bug again - this time it recovered by itself after some dozen minutes or so.

[pawlosck]

I am using floccus 4.17.1 with merge mode. Since about two months or more, everything is ok. One minute ago I checked adding new bookmark and removing bookmark from nextcloud and no problems.

[marcelklehr]

Since #1011 was fixed can you confirm whether this issue is resolved with the latest version of floccus as well?