[Bug 1840348] Re: Sharded OpWQ drops suicide_grace after waiting for work

[Brian Murray]

Hello Kellen, or anyone else affected,

Accepted ceph into bionic-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/ceph/12.2.13-0ubuntu0.18.04.9 in a
few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
bionic to verification-done-bionic. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-bionic. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: ceph (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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https://bugs.launchpad.net/bugs/1840348

Title:
  Sharded OpWQ drops suicide_grace after waiting for work

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive queens series:
  In Progress
Status in Ubuntu Cloud Archive rocky series:
  Won't Fix
Status in Ubuntu Cloud Archive stein series:
  Won't Fix
Status in Ubuntu Cloud Archive train series:
  Fix Released
Status in ceph package in Ubuntu:
  Fix Released
Status in ceph source package in Bionic:
  Fix Committed
Status in ceph source package in Eoan:
  Won't Fix
Status in ceph source package in Focal:
  Fix Released

Bug description:
  [Impact]
  The Sharded OpWQ will opportunistically wait for more work when processing an empty queue. While waiting, the heartbeat timeout and suicide_grace values are modified. The `threadpool_default_timeout` grace is left applied and suicide_grace is disabled.

  After finding work, the original work queue grace/suicide_grace values
  are not re-applied. This can result in hung operations that do not
  trigger an OSD suicide recovery.

  The missing suicide recovery was observed on Luminous 12.2.11. The
  environment was consistently hitting a known authentication race
  condition (issue#37778 [0]) due to repeated OSD service restarts on a
  node exhibiting MCEs from a faulty DIMM.

  The auth race condition would stall pg operations. In some cases, the
  hung ops would persist for hours without suicide recovery.

  [Test Case]
  I have not identified a reliable reproducer. Currently testing the fix by exercising I/O. 

  Recommend letting this bake upstream before considering a back-port.

  [Regression Potential]
  This fix improves suicide_grace coverage of the Sharded OpWq.

  This change is made in a critical code path that drives client I/O. An
  OSD suicide will trigger a service restart and repeated restarts
  (flapping) will adversely impact cluster performance.

  The fix mitigates risk by keeping the applied suicide_grace value
  consistent with the value applied before entering
  `OSD::ShardedOpWQ::_process()`. The fix is also restricted to the
  empty queue edge-case that drops the suicide_grace timeout. The
  suicide_grace value is only re-applied when work is found after
  waiting on an empty queue.

  - In-Progress -
  Opened upstream tracker for issue#45076 [1] and fix pr#34575 [2]

  [0] https://tracker.ceph.com/issues/37778
  [1] https://tracker.ceph.com/issues/45076
  [2] https://github.com/ceph/ceph/pull/34575

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