Bug 1880309

Summary:	[release 4.5] cluster-csi-snapshot-controller-operator: Fix bug in reflector not recovering from "Too large resource version"
Product:	OpenShift Container Platform	Reporter:	Lukasz Szaszkiewicz <lszaszki>
Component:	Storage	Assignee:	Jan Safranek <jsafrane>
Storage sub component:	Operators	QA Contact:	Wei Duan <wduan>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	high
Priority:	high	CC:	aos-bugs, jsafrane
Version:	4.5	Keywords:	Reopened
Target Milestone:	---
Target Release:	4.5.z
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	No Doc Update
Doc Text:		Story Points:	---
Clone Of:
Clones:	1881134 (view as bug list)		Environment:
Last Closed:	2020-10-12 15:47:56 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1880369
Bug Blocks:	1879901, 1881134

Description Lukasz Szaszkiewicz 2020-09-18 09:32:29 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-csi-snapshot-controller-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 Jan Safranek 2020-09-22 11:12:08 UTC

cluster-csi-snapshot-controller-operator in 4.5.z uses k8s.io/client-go v0.17.1. According to https://github.com/kubernetes/kubernetes/pull/92537, 1.17 is not affected. And I checked that there is no DefaultWatchErrorHandler to fix.

Comment 3 Lukasz Szaszkiewicz 2020-09-22 11:16:40 UTC

(In reply to Jan Safranek from comment #2)
> cluster-csi-snapshot-controller-operator in 4.5.z uses k8s.io/client-go
> v0.17.1. According to https://github.com/kubernetes/kubernetes/pull/92537,
> 1.17 is not affected. And I checked that there is no
> DefaultWatchErrorHandler to fix.

The OpenShift API servers in 4.5 are affected. They can send an error msg that the informers must understand and recover from. Please update client-go in 4.5 at least to 1.18.6

Comment 5 Wei Duan 2020-09-27 08:51:27 UTC

Verified on 4.5.0-0.nightly-2020-09-26-194704

In go.mod, the k8s.io/client-go and releated k8s.io version are set to v0.18.6.

Comment 6 Wei Duan 2020-09-27 10:47:26 UTC

Did some snapshot basic test, no issue found.
Updated status to "VERIFIED"

Comment 9 errata-xmlrpc 2020-10-12 15:47:56 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 4.5.14 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-2020:3843