We've recently upgraded to Moodle 3.7 with Adaptable V2 on rebuilt servers, since we've gone live we have been seeing two really problematic issues:
1) Need to login twice to be able to get in (just loops on the login page) -> this seems linked to the logintoken (https://docs.moodle.org/dev/Login_token) being cached somewhere but it doesn't matter if user has visited site before or not.
2) Session Timeouts occurring randomly
We're only seeing the issue on production and not on pre-prod (server setup identical, code nearly identical -> includes a few minor bug fixes we are deploying to prod next week).
We've managed to confirm / reproduce the issue reliably by using this Firefox plugin - https://addons.mozilla.org/en-GB/firefox/addon/auto-reload-tab/
The issue does not occur when using Adaptable & disabling browser cache
The issue does not occur when using Boost (with or without browser cache enabled)
The issue occurs with Adaptable and browser cache enabled.
The issue never occurs regardless of themes & caching.
While I am staring at the theme as a potential culprit, we don't see the issue in any other environments so it's clearly not that simple.
We use Redis for Session caching (on the NFS server) and file caches for everything else. Have moved to using localcache on each of the app servers. While we do need to look at using Redis for more caching types, it seems like a potential distraction from the problem at hand right now.
Would really appreciate any advice in how to pinpoint this issue any further. We essentially have 2-3 weeks to resolve this before term starts.
N.B. We have had performance issues post-upgrade with the NFS mounts being NFS4 and have downgraded these to NFS3.