Bug 1894666

Summary: [release 4.5] cluster-policy-controller: Fix bug in reflector not recovering from "Too large resource version"
Product: OpenShift Container Platform Reporter: Lukasz Szaszkiewicz <lszaszki>
Component: kube-controller-managerAssignee: Maciej Szulik <maszulik>
Status: CLOSED ERRATA QA Contact: RamaKasturi <knarra>
Severity: high Docs Contact:
Priority: high    
Version: 4.5CC: aos-bugs, knarra, mfojtik, palonsor, yinzhou
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Target Release: 4.5.z   
Hardware: Unspecified   
OS: Unspecified   
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Last Closed: 2020-11-17 16:06:00 UTC Type: Bug
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Bug Depends On: 1880369    
Bug Blocks: 1879901    

Description Lukasz Szaszkiewicz 2020-11-04 18:04:22 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-policy-controller 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 3 RamaKasturi 2020-11-09 09:47:11 UTC 
Verified with the payload below and i see that fix is present

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

[knarra@knarra cluster-policy-controller]$ oc adm release info --commits registry.svc.ci.openshift.org/ocp/release:4.5.0-0.nightly-2020-11-07-002125 | grep cluster-policy
  cluster-policy-controller                      https://github.com/openshift/cluster-policy-controller                      f2c27800b9b7b4691829b06951aa2db4195c3837

[knarra@knarra cluster-policy-controller]$ grep 'k8s.io/client-go ' go.mod
	k8s.io/client-go v0.18.10
	k8s.io/client-go => k8s.io/client-go v0.18.10

[knarra@knarra cluster-policy-controller]$  git log --date local --pretty="%h %an %cd - %s" f2c27800 | grep "#46"
f2c27800 OpenShift Merge Robot Thu Nov 5 20:12:47 2020 - Merge pull request #46 from soltysh/bug1894666

Based on the above moving bug to verified state
Comment 6 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