Server(s) unavailable to complete operation only sometimes on Murder cluster

[Torsten Schlabach]

Hi all!

We run a Cyrus Murder setup.

Right now, we have a frontend which is 2.2.13, one backend which is also
2.2.13 and one backend which is 2.1.18.

This works quite well most of the time.

Just very seldom we see the "Server(s) unavailable to complete
operation" when an IMAP client tried to connect through the frontend. In
many cases, a simple retry after some seconds (like a reload in the
webmailer or just clicking on the mailbox once again on the MUA) makes
the problem go away and everything works fine.

It's a bit hard to do any diag as long as it's basically impossible to
provoke this problem.

And what's even more strange: I had a look at the frontend's logs right
after I had the error message myself this morning. Just nothing in the
logs that looks like an error message.

Any hints where to search?

Regards,
Torsten