High CPU at startup and wake

[Andrew E]

Hi all,

Firstly, sorry for posting this previously on the dev channel.

Our issue...

We use CouchDB (3.1.0) on Windows and Linux.

We have noticed that on Windows startup and wake from hibernate, Couch
sometimes "goes bananas" for a period of time.

By that I mean it shows a CPU load of >30% for 10-20 minutes on a
reasonably spec'd Windows developer laptop. After that period, erl.exe goes
to a normal "almost invisible" CPU level.

The active task list is shown as empty in Fauxton.

In Production the Windows instances are on vehicles that are not reachable
on the network for hours at a time while collecting data. They replicate to
the Linux servers when the network is present. Those computers are
underpowered compared to development laptops, which means they are barely
usable when Couch grinds like this.

Any ideas what could be going on or how to find out?

Thank you!
Andrew

[Jan Lehnardt]

Heya,

The last time we fixed something along these lines was in 2019:

https://github.com/apache/couchdb/pull/2195/files

Which predates 3.1.0:

https://blog.couchdb.org/2020/05/06/3-0-1-3-1-0/

Are you 100% sure about your version?

A quick look does not suggest we have introduced this pattern again
since.

But CouchDB should behave fine in your scenario.

Can you try and remsh into the node and see which erlang processes
are hogging the CPU?

Also we should move this to the bug tracker if you can reproduce this
on 3.3.2.

Best
Jan
—

[Andrew E]

Hi Jan

Thank you for the reply.

Version 3.1. is definite, on both Windows and Linux.

Can you point me toward notes on remsh? Very happy to try to reproduce it,
though we haven't found reliable steps to do that yet.

Thanks
Andrew