[ceph-users] ceph-mgr hangs on larger clusters in Luminous

Bryan Stillwell bstillwell at godaddy.com
Thu Oct 18 12:39:38 PDT 2018

I left some of the 'ceph pg dump' commands running and twice they returned results after 30 minutes, and three times it took 45 minutes.  Is there something that runs every 15 minutes that would let these commands finish?


From: Bryan Stillwell <bstillwell at godaddy.com>
Date: Thursday, October 18, 2018 at 11:16 AM
To: "ceph-users at lists.ceph.com" <ceph-users at lists.ceph.com>
Subject: ceph-mgr hangs on larger clusters in Luminous

After we upgraded from Jewel (10.2.10) to Luminous (12.2.5) we started seeing a problem where the new ceph-mgr would sometimes hang indefinitely when doing commands like 'ceph pg dump' on our largest cluster (~1,300 OSDs).  The rest of our clusters (10+) aren't seeing the same issue, but they are all under 600 OSDs each.  Restarting ceph-mgr seems to fix the issue for 12 hours or so, but usually overnight it'll get back into the state where the hang reappears.  At first I thought it was a hardware issue, but switching the primary ceph-mgr to another node didn't fix the problem.
I've increased the logging to 20/20 for debug_mgr, and while a working dump looks like this:
2018-10-18 09:26:16.256911 7f9dbf5e7700  4 mgr.server handle_command decoded 3
2018-10-18 09:26:16.256917 7f9dbf5e7700  4 mgr.server handle_command prefix=pg dump
2018-10-18 09:26:16.256937 7f9dbf5e7700 10 mgr.server _allowed_command  client.admin capable
2018-10-18 09:26:16.256951 7f9dbf5e7700  0 log_channel(audit) log [DBG] : from='client.1414554763' entity='client.admin' cmd=[{"prefix": "pg dump", "target": ["mgr", ""], "format": "json-pretty"}]: dispatch
2018-10-18 09:26:22.567583 7f9dbf5e7700  1 mgr.server reply handle_command (0) Success dumped all
A failed dump call doesn't show up at all.  The "mgr.server handle_command prefix=pg dump" log entry doesn't seem to even make it to the logs.
This problem also continued to appear after upgrading to 12.2.8.
Has anyone else seen this?

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