Another possible cause (we currently see it on one of our clusters): delays in ldap lookups.
We have sssd on the machines, and occasionally, when sssd contacts the ldap server, it takes 5 or 10 seconds (or even 15) before it gets an answer. If that happens because slurmctld is trying to look up some user or group, etc, client commands depending on it will hang. The default message timeout is 10 seconds, so if the delay is more than that, you get the timeout error. We don't know why the delays are happening, but while we are debugging it, we've increased the MessageTimeout, which seems to have reduced the problem a bit. We're also experimenting with GroupUpdateForce and GroupUpdateTime to reduce the number of times slurmctld needs to ask about groups, but I'm unsure how much that helps. -- Bjørn-Helge Mevik, dr. scient, Department for Research Computing, University of Oslo
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