Bug 1880326 - [release 4.5] cluster-kube-scheduler-operator: Fix bug in reflector not recovering from "Too large resource version"
Summary: [release 4.5] cluster-kube-scheduler-operator: Fix bug in reflector not recov...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: kube-scheduler
Version: 4.5
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: ---
: 4.5.z
Assignee: Maciej Szulik
QA Contact: RamaKasturi
URL:
Whiteboard:
Depends On: 1880369
Blocks: 1879901
TreeView+ depends on / blocked
 
Reported: 2020-09-18 09:58 UTC by Lukasz Szaszkiewicz
Modified: 2021-08-25 07:26 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2020-11-17 16:06:00 UTC
Target Upstream Version:
Embargoed:


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System ID Private Priority Status Summary Last Updated
Github openshift cluster-kube-scheduler-operator pull 287 0 None closed [release-4.5] Bug 1880326: fix bug in reflector not recovering from "Too large reso… 2020-12-04 12:00:57 UTC
Github openshift origin pull 25603 0 None closed [release-4.5] Bug 1880326: Backport disruption test improvements 2020-12-04 12:00:57 UTC
Red Hat Product Errata RHBA-2020:5051 0 None None None 2020-11-17 16:06:29 UTC

Description Lukasz Szaszkiewicz 2020-09-18 09:58:06 UTC
A recent fix in the reflector/informer https://github.com/kubernetes/kubernetes/pull/92688 prevents components/operators from entering a hotloop and stuck.

There are already reported cases that have run into that issue and were stuck for hours or even days. For example https://bugzilla.redhat.com/show_bug.cgi?id=1877346.

The root cause of the issue is the fact that a watch cache is initialized from the global revision (etcd) and might stay on it for an undefined period (if no changes were (add, modify) made). 
That means that the watch cache across server instances may be out of sync. 
That might lead to a situation in which a client gets a resource version from a server that has observed a newer rv, disconnect (due to a network error) from it, and reconnect to a server that is behind, resulting in “Too large resource version“ errors.

More details in https://github.com/kubernetes/kubernetes/issues/91073 and https://github.com/kubernetes/enhancements/tree/master/keps/sig-api-machinery/1904-efficient-watch-resumption


It looks like the issue only affects 1.18. According to https://github.com/kubernetes/kubernetes/issues/91073#issuecomment-652251669 the issue was first introduced in that version by changes done to the reflector. 
The fix is already present in 1.19.


Please make sure that cluster-kube-scheduler-operator is using a client-go that includes https://github.com/kubernetes/kubernetes/pull/92688 if not please use this BZ and file a PR.
In case you are using a framework to build your operator make sure it uses the right version of the client-go library.

Comment 2 Maciej Szulik 2020-10-01 14:18:50 UTC
PR in the queue.

Comment 3 Maciej Szulik 2020-10-23 10:30:09 UTC
PR in the queue.

Comment 5 RamaKasturi 2020-11-09 09:52:53 UTC
Verified with payload below and i see that fix is present

4.5.0-0.nightly-2020-11-07-002125


[knarra@knarra cluster-kube-scheduler-operator]$ oc adm release info --commits registry.svc.ci.openshift.org/ocp/release:4.5.0-0.nightly-2020-11-07-002125 | grep cluster-kube-scheduler-operator
  cluster-kube-scheduler-operator                https://github.com/openshift/cluster-kube-scheduler-operator                a8218a72d631f93990c46f1337873954b2e66d88
[knarra@knarra cluster-kube-scheduler-operator]$ grep 'k8s.io/client-go ' go.mod
	k8s.io/client-go v0.18.9
[knarra@knarra cluster-kube-scheduler-operator]$ git log --date local --pretty="%h %an %cd - %s" a8218a7 | grep "#287"
c419f3bd OpenShift Merge Robot Thu Oct 15 07:09:40 2020 - Merge pull request #287 from soltysh/bug1880326

Based on the above moving bug to verified state.

Comment 8 errata-xmlrpc 2020-11-17 16:06:00 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (OpenShift Container Platform 4.5.19 bug fix update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:5051

Comment 9 RamaKasturi 2021-08-25 07:26:22 UTC
Setting qe_test_coverage flag to '+' as i see that regression test coverage would be sufficient to test this bug.


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