[Presence] Huge spike in CPU usage/Federation traffic approximately every 25 minutes

[matrixbot]

This issue has been migrated from #15878.

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There is a timeout for when to send a ping over federation every 25 minutes that keeps a user from being marked 'offline' before the 30 minute timeout hits.

This appears to be the replication notifier system ramping up and queueing a bunch of federation sending requests over approximately 1 minute worth of time(give or take a few seconds)

Images

There is a database hit during this to get_current_hosts_in_room(), I'm not personally convinced it's contributing to the seriousness of this situation(but included here for completeness).

Images:

UPDATE: Additional information from the other side of the slash in the title

The large spike in traffic caused by queueing and then sending all those requests looks like this:

[realtyem]

This can be closed as it is the nature of how presence updates are sent. To change this would require a spec change to use a meshing network of communication, which would probably be a privacy violation(never mind how brittle it could end up). Someone else's homeserver shouldn't be handling/forwarding my presence for me.