[Bug 1906496] Re: [SRU] mgr can be very slow in a large ceph cluster
Corey Bryant
1906496 at bugs.launchpad.net
Fri Dec 11 17:56:51 UTC 2020
** Also affects: ceph (Ubuntu Groovy)
Importance: Undecided
Status: New
** Also affects: ceph (Ubuntu Hirsute)
Importance: High
Assignee: Ponnuvel Palaniyappan (pponnuvel)
Status: Fix Released
** Also affects: ceph (Ubuntu Focal)
Importance: Undecided
Status: New
** Changed in: ceph (Ubuntu Groovy)
Status: New => Fix Released
** Changed in: ceph (Ubuntu Focal)
Status: New => Fix Released
** Also affects: cloud-archive/stein
Importance: Undecided
Status: New
** Also affects: cloud-archive/victoria
Importance: Undecided
Status: New
** Also affects: cloud-archive/ussuri
Importance: Undecided
Status: New
** Also affects: cloud-archive/queens
Importance: Undecided
Status: New
** Also affects: cloud-archive/train
Importance: Undecided
Status: New
** No longer affects: cloud-archive/victoria
** Changed in: cloud-archive/ussuri
Status: New => Fix Released
** Changed in: cloud-archive/train
Status: New => Fix Released
** Changed in: cloud-archive/stein
Importance: Undecided => High
** Changed in: cloud-archive/stein
Status: New => Triaged
** Changed in: cloud-archive/queens
Importance: Undecided => High
** Changed in: cloud-archive/queens
Status: New => Triaged
** Changed in: cloud-archive
Status: New => Fix Released
** Changed in: ceph (Ubuntu Bionic)
Importance: Medium => High
** Changed in: ceph (Ubuntu Bionic)
Status: New => Triaged
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https://bugs.launchpad.net/bugs/1906496
Title:
[SRU] mgr can be very slow in a large ceph cluster
Status in Ubuntu Cloud Archive:
Fix Released
Status in Ubuntu Cloud Archive queens series:
Triaged
Status in Ubuntu Cloud Archive stein series:
Triaged
Status in Ubuntu Cloud Archive train series:
Fix Released
Status in Ubuntu Cloud Archive ussuri series:
Fix Released
Status in ceph package in Ubuntu:
Fix Released
Status in ceph source package in Bionic:
Triaged
Status in ceph source package in Focal:
Fix Released
Status in ceph source package in Groovy:
Fix Released
Status in ceph source package in Hirsute:
Fix Released
Bug description:
[Impact]
Ceph upstream implemented a new feature [1] that will check/report those long network ping times between osds, but it introduced an issue that ceph-mgr might be very slow because it needs to dump all the new osd network ping stats [2] for some tasks, this can be bad especially when the cluster has large number of osds.
Since these kind osd network ping stats doesn't need to be exposed to
the python mgr module. so, it only makes the mgr doing more work than
it needs to, it could cause the mgr slow or even hang and could cause
the cpu usage of mgr process constantly high. The fix is to disable
the ping time dump for those mgr python modules.
This resulted in ceph-mgr not responding to commands and/or hanging
(and had to be restarted) in clusters with a large number of OSDs.
[0] is the upstreambug. It was backported to Nautilus but rejected for
Luminous and Mimic because they reached EOL in upstream. But I want to
backport to these two releases Ubuntu/UCA.
The major fix from upstream is here [3], and also I found an
improvement commit [4] that submitted later in another PR.
[Test Case]
Deploy a Ceph cluster (Luminous 13.2.9 or Mimic 13.2.9) with large number of Ceph OSDs (600+). During normal operations of the cluster, as the ceph-mgr dumps the network ping stats regularly, this problem would manifest. This is relatively hard to reproduce as the ceph-mgr may not always get overloaded and thus not hang.
[Regression Potential]
Fix has been accepted upstream (the changes are here in "sync" with upstream to the extent these old releases match the latest source code) and have been confirmed to work. So the risk is minimal.
At worst, this could affect modules that consume the stats from ceph-
mgr (such as prometheus or other monitoring scripts/tools) and thus
becomes less useful. But still shouldn't cause any problems to the
operations of the cluster itself.
[Other Info]
- In addition to the fix from [1], another commit [4] is also cherry-picked and backported here - this was also accepted upstream.
- Since the ceph-mgr hangs when affected, this also impact sosreport
collection - commands time out as the mgr doesn't respond and thus
info get truncated/not collected in that case. This fix should help
avoid that problem in sosreports.
[0] https://tracker.ceph.com/issues/43364
[1] https://github.com/ceph/ceph/pull/28755
[2] https://github.com/ceph/ceph/pull/28755/files#diff-5498d83111f1210998ee186e98d5836d2bce9992be7648addc83f59e798cddd8L430
[3] https://github.com/ceph/ceph/pull/32406
[4] https://github.com/ceph/ceph/pull/32554/commits/1112584621016c4a8cac1bedb1a1b8b17c394f7f
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