Slow first connect after reopening app

[nisbet-hubbard]

Steps to reproduce

Closing and reopening app without using VPN

Outcome

What did you expect?

Syncing appears briefly

What happened instead?

Stuck at Syncing for 8 minutes. Potentially related to #3316.

Your phone model

No response

Operating system version

No response

Application version

1.9.1

Homeserver

conduwuit

Will you send logs?

Yes

[pixlwave]

Heads up that #3316 has zero effect when a user is already logged in.

[nisbet-hubbard]

You're absolutely right.

I mentioned it only because the kind of behaviour I'm observing (fast connect within hours, long wait when connecting after a day or so) seems to suggest Element is making a similar blocked request each time it connects to the homeserver after a long hiatus.

[pixlwave]

Looking at your logs, they're filled with TimedOut errors on /_matrix/client/unstable/org.matrix.msc3575/sync and other endpoints like /_matrix/client/v3/room_keys/keys/…, /_matrix/client/v3/keys/query etc. Closing this as a backend issue.

[nisbet-hubbard]

Glad the issue lies elsewhere. How should I go about debugging this?

Since /org.matrix.msc3575/ is involved here, would it be a good idea to just wait for conduwuit to implement the new sliding sync? Or should I report the issue now?

[pixlwave]

There's a chance this is in some way related to #3478

[nisbet-hubbard]

Thanks for the pointer!

As killing the app in this case doesn't seem to improve the timeouts, we can probably rule out that possibility.

Having had more time to debug this, I've finally identified Cloudflare as the blocker (even though the requests aren't blocked as such). Removing Cloudflare from the chain also enables the use of mobile-optimised algorithms like ChaCha20-Poly1305, as the homeserver no longer has to talk to a server.

So, these might be other reasons for not using CF for Matrix.