[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Chris MacNaughton]

** Changed in: cloud-archive/kilo
   Status: Fix Committed => Fix Released

** Changed in: cloud-archive
   Status: Fix Committed => Fix Released

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[James Page]

This bug was fixed in the package python-oslo.messaging - 4.6.1-2ubuntu2~cloud0
---

 python-oslo.messaging (4.6.1-2ubuntu2~cloud0) trusty-mitaka; urgency=medium
 .
   * New update for the Ubuntu Cloud Archive.
 .
 python-oslo.messaging (4.6.1-2ubuntu2) xenial; urgency=medium
 .
   * d/p/rabbit-avoid-busy-loop.patch: Cherry pick patch from upstream
 to avoid rabbit driver busy loop on epoll_wait with heartbeat+eventlet
 (LP: #1518430).


** Changed in: cloud-archive/mitaka
   Status: Fix Committed => Fix Released

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Tags removed: verification-mitaka-needed
** Tags added: verification-mitaka-done

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[James Page]

This bug was fixed in the package python-oslo.messaging - 2.5.0-1ubuntu2~cloud1
---

 python-oslo.messaging (2.5.0-1ubuntu2~cloud1) trusty-liberty; urgency=medium
 .
   * d/p/rabbit-avoid-busy-loop.patch: Cherry pick patch from upstream
 stable/mitaka branch to avoid rabbit driver busy loop on epoll_wait with
 heartbeat+eventlet (LP: #1518430).


** Changed in: cloud-archive/liberty
   Status: Fix Committed => Fix Released

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[James Page]

This bug was fixed in the package python-oslo.messaging - 5.10.0-0ubuntu2~cloud0
---

 python-oslo.messaging (5.10.0-0ubuntu2~cloud0) xenial-newton; urgency=medium
 .
   * New update for the Ubuntu Cloud Archive.
 .
 python-oslo.messaging (5.10.0-0ubuntu2) yakkety; urgency=medium
 .
   * d/p/rabbit-avoid-busy-loop.patch: Cherry pick patch from upstream
 to avoid rabbit driver busy loop on epoll_wait with heartbeat+eventlet
 (LP: #1518430).


** Changed in: cloud-archive/newton
   Status: Fix Committed => Fix Released

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Tags removed: verification-liberty-needed
** Tags added: verification-liberty-done

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Launchpad Bug Tracker]

This bug was fixed in the package python-oslo.messaging - 4.6.1-2ubuntu2

---
python-oslo.messaging (4.6.1-2ubuntu2) xenial; urgency=medium

  * d/p/rabbit-avoid-busy-loop.patch: Cherry pick patch from upstream
to avoid rabbit driver busy loop on epoll_wait with heartbeat+eventlet
(LP: #1518430).

 -- Corey Bryant   Fri, 02 Dec 2016 12:51:26
-0500

** Changed in: python-oslo.messaging (Ubuntu Xenial)
   Status: Fix Committed => Fix Released

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Launchpad Bug Tracker]

This bug was fixed in the package python-oslo.messaging -
5.10.0-0ubuntu2

---
python-oslo.messaging (5.10.0-0ubuntu2) yakkety; urgency=medium

  * d/p/rabbit-avoid-busy-loop.patch: Cherry pick patch from upstream
to avoid rabbit driver busy loop on epoll_wait with heartbeat+eventlet
(LP: #1518430).

 -- Corey Bryant   Fri, 02 Dec 2016 12:39:50
-0500

** Changed in: python-oslo.messaging (Ubuntu Yakkety)
   Status: Fix Committed => Fix Released

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

Marked as verifcation-done as this has passed tests on xenial and
yakkety. We perform regression testing by juju deploying two openstack
clouds, one against -proposed and one against -updates, and we then run
tempest integration smoke tests[1] to verify those deployed clouds, and
evaluate any differences in results. [1]
https://github.com/openstack/tempest/blob/master/README.rst

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Tags removed: verification-needed
** Tags added: verification-done

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Changed in: cloud-archive
   Importance: Undecided => Medium

** Changed in: cloud-archive/kilo
   Importance: Undecided => Medium

** Changed in: cloud-archive/liberty
   Importance: Undecided => Medium

** Changed in: cloud-archive/mitaka
   Importance: Undecided => Medium

** Changed in: cloud-archive/newton
   Importance: Undecided => Medium

** Changed in: python-oslo.messaging (Ubuntu Xenial)
   Importance: Undecided => Medium

** Changed in: python-oslo.messaging (Ubuntu Yakkety)
   Importance: Undecided => Medium

** Changed in: python-oslo.messaging (Ubuntu Zesty)
   Importance: Undecided => Medium

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Brian Murray]

Hello JuanJo, or anyone else affected,

Accepted python-oslo.messaging into yakkety-proposed. The package will
build now and be available at https://launchpad.net/ubuntu/+source
/python-oslo.messaging/5.10.0-0ubuntu2 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 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, and change the tag
from verification-needed to verification-done. If it does not fix the
bug for you, please add a comment stating that, and change the tag to
verification-failed.  In either case, details of your testing will help
us make a better decision.

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

** Changed in: python-oslo.messaging (Ubuntu Yakkety)
   Status: New => Fix Committed

** Tags added: verification-needed

** Changed in: python-oslo.messaging (Ubuntu Xenial)
   Status: New => Fix Committed

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Mathew Hodson]

** Project changed: nova => ubuntu-translations

** No longer affects: ubuntu-translations

** No longer affects: nova (Ubuntu)

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

This has been uploaded to ubuntu zesty, yakkety, xenial and is awaiting
sru team review for yakkety and xenial.  This has also been uploaded to
kilo-staging and liberty-staging for the ubuntu cloud archive.  These
should all be available in -proposed soon for testing.

** Also affects: cloud-archive/kilo
   Importance: Undecided
   Status: New

** Changed in: cloud-archive/kilo
   Status: New => Fix Committed

** Changed in: cloud-archive/liberty
   Status: New => Fix Committed

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

Ubuntu SRU details:
[Description]
Avoid busy loop on epoll_wait with heartbeat+eventlet in rabbit driver.

[Test Case]
See bug description.

[Regression Potential]
Minimal as the patches are cherry picked from upstream stable branches.

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

I can't see where this bug exists on base Trusty/Icehouse so I've
dropped those targets for Ubuntu.

** No longer affects: cloud-archive/icehouse

** No longer affects: python-oslo.messaging (Ubuntu Trusty)

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Changed in: python-oslo.messaging (Ubuntu Zesty)
   Status: New => Fix Released

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[OpenStack Infra]

Reviewed:  https://review.openstack.org/395018
Committed: 
https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=d690cac08ca0f6c18518e7760d8bdcfd14cdee84
Submitter: Jenkins
Branch:stable/mitaka

commit d690cac08ca0f6c18518e7760d8bdcfd14cdee84
Author: John Eckersberg 
Date:   Fri Oct 14 11:02:47 2016 -0400

rabbit: Avoid busy loop on epoll_wait with heartbeat+eventlet

Calling threading.Event.wait() when using eventlet results in a busy
loop calling epoll_wait, because the Python 2.x
threading.Condition.wait() implementation busy-waits by calling
sleep() with very small values (0.0005..0.05s).  Because sleep() is
monkey-patched by eventlet, this results in many very short timers
being added to the eventlet hub, and forces eventlet to constantly
epoll_wait looking for new data unecessarily.

This utilizes a new Event from eventletutils which conditionalizes the
event primitive depending on whether or not eventlet is being used.
If it is, eventlet.event.Event is used instead of threading.Event.
The eventlet.event.Event implementation does not suffer from the same
busy-wait sleep problem.  If eventlet is not used, the previous
behavior is retained.

For Newton backport, this bundles the Event from eventletutils
directly in oslo.messaging under the _utils module.  It is taken from:

https://review.openstack.org/#/c/389739/

combined with the followup fix:

https://review.openstack.org/#/c/394460/

Change-Id: I5c211092d282e724d1c87ce4d06b6c44b592e764
Depends-On: Id33c9f8c17102ba1fe24c12b053c336b6d265501
Closes-bug: #1518430
(cherry picked from commit a6c193f3eba62cdcbfe04d0fa93e95352bcfb1c3)


** Changed in: cloud-archive/mitaka
   Status: New => Fix Committed

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[OpenStack Infra]

Reviewed:  https://review.openstack.org/394963
Committed: 
https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=f4bf955879747338b0ab7a6ca41d0dea74508353
Submitter: Jenkins
Branch:stable/newton

commit f4bf955879747338b0ab7a6ca41d0dea74508353
Author: John Eckersberg 
Date:   Fri Oct 14 11:02:47 2016 -0400

rabbit: Avoid busy loop on epoll_wait with heartbeat+eventlet

Calling threading.Event.wait() when using eventlet results in a busy
loop calling epoll_wait, because the Python 2.x
threading.Condition.wait() implementation busy-waits by calling
sleep() with very small values (0.0005..0.05s).  Because sleep() is
monkey-patched by eventlet, this results in many very short timers
being added to the eventlet hub, and forces eventlet to constantly
epoll_wait looking for new data unecessarily.

This utilizes a new Event from eventletutils which conditionalizes the
event primitive depending on whether or not eventlet is being used.
If it is, eventlet.event.Event is used instead of threading.Event.
The eventlet.event.Event implementation does not suffer from the same
busy-wait sleep problem.  If eventlet is not used, the previous
behavior is retained.

For Newton backport, this bundles the Event from eventletutils
directly in oslo.messaging under the _utils module.  It is taken from:

https://review.openstack.org/#/c/389739/

combined with the followup fix:

https://review.openstack.org/#/c/394460/

Change-Id: I5c211092d282e724d1c87ce4d06b6c44b592e764
Depends-On: Id33c9f8c17102ba1fe24c12b053c336b6d265501
Closes-bug: #1518430
(cherry picked from commit a6c193f3eba62cdcbfe04d0fa93e95352bcfb1c3)


** Changed in: cloud-archive/newton
   Status: New => Fix Committed

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Also affects: cloud-archive
   Importance: Undecided
   Status: New

** Also affects: cloud-archive/newton
   Importance: Undecided
   Status: New

** Also affects: cloud-archive/icehouse
   Importance: Undecided
   Status: New

** Also affects: cloud-archive/liberty
   Importance: Undecided
   Status: New

** Also affects: cloud-archive/mitaka
   Importance: Undecided
   Status: New

** Also affects: nova (Ubuntu Zesty)
   Importance: Undecided
   Status: Invalid

** Also affects: python-oslo.messaging (Ubuntu Zesty)
   Importance: Undecided
   Status: New

** Also affects: nova (Ubuntu Xenial)
   Importance: Undecided
   Status: New

** Also affects: python-oslo.messaging (Ubuntu Xenial)
   Importance: Undecided
   Status: New

** Also affects: nova (Ubuntu Trusty)
   Importance: Undecided
   Status: New

** Also affects: python-oslo.messaging (Ubuntu Trusty)
   Importance: Undecided
   Status: New

** Also affects: nova (Ubuntu Yakkety)
   Importance: Undecided
   Status: New

** Also affects: python-oslo.messaging (Ubuntu Yakkety)
   Importance: Undecided
   Status: New

** No longer affects: nova (Ubuntu Trusty)

** No longer affects: nova (Ubuntu Xenial)

** No longer affects: nova (Ubuntu Yakkety)

** No longer affects: nova (Ubuntu Zesty)

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[OpenStack Infra]

Reviewed:  https://review.openstack.org/386656
Committed: 
https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=a6c193f3eba62cdcbfe04d0fa93e95352bcfb1c3
Submitter: Jenkins
Branch:master

commit a6c193f3eba62cdcbfe04d0fa93e95352bcfb1c3
Author: John Eckersberg 
Date:   Fri Oct 14 11:02:47 2016 -0400

rabbit: Avoid busy loop on epoll_wait with heartbeat+eventlet

Calling threading.Event.wait() when using eventlet results in a busy
loop calling epoll_wait, because the Python 2.x
threading.Condition.wait() implementation busy-waits by calling
sleep() with very small values (0.0005..0.05s).  Because sleep() is
monkey-patched by eventlet, this results in many very short timers
being added to the eventlet hub, and forces eventlet to constantly
epoll_wait looking for new data unecessarily.

This utilizes a new Event from eventletutils which conditionalizes the
event primitive depending on whether or not eventlet is being used.
If it is, eventlet.event.Event is used instead of threading.Event.
The eventlet.event.Event implementation does not suffer from the same
busy-wait sleep problem.  If eventlet is not used, the previous
behavior is retained.

Change-Id: I5c211092d282e724d1c87ce4d06b6c44b592e764
Depends-On: Id33c9f8c17102ba1fe24c12b053c336b6d265501
Closes-bug: #1518430


** Changed in: oslo.messaging
   Status: In Progress => Fix Released

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[John Eckersberg]

** Changed in: oslo.messaging
 Assignee: (unassigned) => John Eckersberg (jeckersb)

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Gevorg Davoian]

** Changed in: oslo.messaging
 Assignee: Gevorg Davoian (gdavoian) => (unassigned)

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[OpenStack Infra]

** Changed in: oslo.messaging
 Assignee: John Eckersberg (jeckersb) => Gevorg Davoian (gdavoian)

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[John Eckersberg]

Copy/paste from https://bugzilla.redhat.com/show_bug.cgi?id=1384183#c10:

In the oslo.messaging rabbit driver, there is a thread for heartbeats:

https://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/_drivers/impl_rabbit.py?id=293084f9b5ef59c4b2dcd8c7180f7053b47337a9#n968

specifically, the three methods, _heartbeat_start, _heartbeat_stop,
and _heartbeat_thread_job.

In _heartbeat_start, it creates a threading.Event (this event ends up
being the root of the problem), a threading.Thread for the heartbeat
thread, and then starts the heartbeat thread.

The heartbeat thread does work, and then at the end executes:

self._heartbeat_exit_event.wait(
timeout=self._heartbeat_wait_timeout)

The _heartbeat_stop method sets the exit event when the connection is
stopped, this is where it receives that and shuts down.

With the default heartbeat configuration, _heartbeat_wait_timeout ends
up being 15.0 seconds.  This sounds reasonable, but explodes under the
hood.

Event.wait() ultimately calls Condition.wait(), which runs this gem[1] of
code:

# Balancing act:  We can't afford a pure busy loop, so we
# have to sleep; but if we sleep the whole timeout time,
# we'll be unresponsive.  The scheme here sleeps very
# little at first, longer as time goes on, but never longer
# than 20 times per second (or the timeout time remaining).
endtime = _time() + timeout
delay = 0.0005 # 500 us -> initial delay of 1 ms
while True:
gotit = waiter.acquire(0)
if gotit:
break
remaining = endtime - _time()
if remaining <= 0:
break
delay = min(delay * 2, remaining, .05)
_sleep(delay)

Now, the problem is that _sleep here is time.sleep, which has been
previously monkey-patched by eventlet to be eventlet.greenthread.sleep
instead.

When you call sleep() in eventlet, it adds a timer onto an internal
heap that it maintains[2].  When the main event loop runs, it checks
whatever the shortest timer is, and uses that delta as the argument
for waiting (this ultimately ends up to epoll_wait).  Here's the
crucial part of the code[3]:

wakeup_when = self.sleep_until()
if wakeup_when is None:
sleep_time = self.default_sleep()
else:
sleep_time = wakeup_when - self.clock()
if sleep_time > 0:
self.wait(sleep_time)
else:
self.wait(0)

Because Condition.wait() uses such small sleep times between
0.0005..0.05, these tiny timers are almost always the next timer to
fire, and sleep_time above ends up being negative (or small enough to
practically be zero anyways).  The self.wait() call propagates down to
epoll_wait() and you get the behavior we're seeing.

So, the root of the problem is that using threading.Event inside of
eventlet is bad.

[1] https://hg.python.org/cpython/file/v2.7.12/Lib/threading.py#l344
[2] 
https://github.com/eventlet/eventlet/blob/7343f2e817fbc09d07c36727dfb2e4655a37901f/eventlet/hubs/hub.py#L389-L392
[3] 
https://github.com/eventlet/eventlet/blob/7343f2e817fbc09d07c36727dfb2e4655a37901f/eventlet/hubs/hub.py#L340-L348

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[John Eckersberg]

** Changed in: oslo.messaging
 Assignee: (unassigned) => John Eckersberg (jeckersb)

** Changed in: oslo.messaging
   Status: Incomplete => In Progress

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[John Eckersberg]

@sileht, looks like it is still valid -
https://bugzilla.redhat.com/show_bug.cgi?id=1384183

** Bug watch added: Red Hat Bugzilla #1384183
   https://bugzilla.redhat.com/show_bug.cgi?id=1384183

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Mehdi Abaakouk]

Is this still valid on Newton/Mitaka ?

** Changed in: oslo.messaging
   Status: New => Won't Fix

** Changed in: oslo.messaging
   Status: Won't Fix => Incomplete

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Chuck Short]

** Changed in: nova (Ubuntu)
   Status: Confirmed => Invalid

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Sean Dague]

This is really an oslo.messaging issue. Not valid for Nova upstream.

** Changed in: nova
   Status: New => Invalid

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[JuanJo Ciarlante]

For experimenting purposes / measuring the difference against
what would be a (better) behaving epoll_wait usage, I created:
https://github.com/jjo/dl-hack-lp1518430
,  which implements hooking epoll_wait() and select() 
(via LD_PRELOAD) to limit the rate of calls with zero timeouts.

WfM'd on an experimental stack, on one node hosting all OS
API LXCs and nova-compute, I measured a 
700K/s -> 120K/s reduction of epoll_wait calls (as shown
by: sysdig -c topscalls).

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Description changed:

  Context: openstack juju/maas deploy using 1510 charms release
  on trusty, with:
    openstack-origin: "cloud:trusty-liberty"
    source: "cloud:trusty-updates/liberty
  
  * Several openstack nova- and neutron- services, at least:
  nova-compute, neutron-server, nova-conductor,
  neutron-openvswitch-agent,neutron-vpn-agent
  show almost busy looping on epoll_wait() calls, with zero timeout set
  most frequently.
  - nova-compute (chose it b/cos single proc'd) strace and ltrace captures:
    http://paste.ubuntu.com/13371248/ (ltrace, strace)
  
  As comparison, this is how it looks on a kilo deploy:
  - http://paste.ubuntu.com/13371635/
  
  * 'top' sample from a nova-cloud-controller unit from
-this completely idle stack:
+    this completely idle stack:
    http://paste.ubuntu.com/13371809/
  
  FYI *not* seeing this behavior on keystone, glance, cinder,
  ceilometer-api.
  
  As this issue is present on several components, it likely comes
  from common libraries (oslo concurrency?), fyi filed the bug to
  nova itself as a starting point for debugging.
+ 
+ Note: The description in the following bug gives a good overview of the
+ issue and points to a possible fix for oslo.messaging:
+ https://bugs.launchpad.net/mos/+bug/1380220

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Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Description changed:

  Context: openstack juju/maas deploy using 1510 charms release
  on trusty, with:
    openstack-origin: "cloud:trusty-liberty"
    source: "cloud:trusty-updates/liberty
  
  * Several openstack nova- and neutron- services, at least:
  nova-compute, neutron-server, nova-conductor,
  neutron-openvswitch-agent,neutron-vpn-agent
  show almost busy looping on epoll_wait() calls, with zero timeout set
  most frequently.
  - nova-compute (chose it b/cos single proc'd) strace and ltrace captures:
    http://paste.ubuntu.com/13371248/ (ltrace, strace)
  
  As comparison, this is how it looks on a kilo deploy:
  - http://paste.ubuntu.com/13371635/
  
  * 'top' sample from a nova-cloud-controller unit from
-this completely idle stack:
+    this completely idle stack:
    http://paste.ubuntu.com/13371809/
  
  FYI *not* seeing this behavior on keystone, glance, cinder,
  ceilometer-api.
  
  As this issue is present on several components, it likely comes
  from common libraries (oslo concurrency?), fyi filed the bug to
  nova itself as a starting point for debugging.
+ 
+ Note: The description in the following bug gives a good overview of the
+ issue and points to a possible fix for oslo.messaging:
+ https://bugs.launchpad.net/mos/+bug/1380220

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Also affects: oslo.messaging
   Importance: Undecided
   Status: New

** Also affects: python-oslo.messaging (Ubuntu)
   Importance: Undecided
   Status: New

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Corey Bryant]

** Also affects: oslo.messaging
   Importance: Undecided
   Status: New

** Also affects: python-oslo.messaging (Ubuntu)
   Importance: Undecided
   Status: New

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Dina Belova]

For MOS it's tracked separately -
https://bugs.launchpad.net/mos/+bug/1380220 - removing from this bug

** No longer affects: mos

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Aleksandr Shaposhnikov]

** Attachment added: "Resource usage"
   
https://bugs.launchpad.net/mos/+bug/1518430/+attachment/4640861/+files/Screen%20Shot%202016-04-20%20at%2010.38.42.png

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Aleksandr Shaposhnikov]

Here is some graphs of resources usage by neutron-server even after full
cleanup (no networks presents in DB)

** Attachment added: "Resourse usage after full cleanup"
   
https://bugs.launchpad.net/mos/+bug/1518430/+attachment/4640860/+files/Screen%20Shot%202016-04-20%20at%2010.38.22.png

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  liberty: ~busy loop on epoll_wait being called with zero timeout

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Roman Podoliaka]

I believe, this is https://bugs.launchpad.net/mos/+bug/1380220

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Aleksandr Shaposhnikov]

I could confirm that I could observe this bug definitely on Liberty on 
following services: neutron-server, nova-conductor. I couldn't confirm that for 
other because it requires additional monitoring/debugging. 
Steps to reproduce for neutron-server:

1.Deploy new cloud.
2. Measure CPU and MEM usage by neutron-server and take a look on strace of any 
pid which is associated with RPC worker.
3. Create 200-400 networks with routers.
4. Spawn 1 vms (not at once, you could just spawn and delete them by 10-20 
pcs).
5. Delete everything (networks, routers, vms).
6. Measure CPU/MEM usage and take a look on strace of neutron-server RPC worker.

Expected behavior:
Everything should be the same as at step 2 with non-significant changes in 
CPU/MEM.

Observer behavior:
Huge CPU load (1-2 cores), huge MEMORY load (6-7Gb) without doing anything 
useful at the moment ;) Stracing of RPC thread will show ~1k per second of 
EPOLL_WAITs with 0 timeout.

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Aleksandr Shaposhnikov]

** Also affects: nova
   Importance: Undecided
   Status: New

** Also affects: mos
   Importance: Undecided
   Status: New

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: nova (Ubuntu)
   Status: New => Confirmed

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[Bug 1518430] Re: liberty: ~busy loop on epoll_wait being called with zero timeout

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: nova (Ubuntu)
   Status: New => Confirmed

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