Bug 1880327

Summary:	[release 4.5] cluster-kube-storage-version-migrator-operator: Fix bug in reflector not recovering from "Too large resource version"
Product:	OpenShift Container Platform	Reporter:	Lukasz Szaszkiewicz <lszaszki>
Component:	kube-storage-version-migrator	Assignee:	Lukasz Szaszkiewicz <lszaszki>
Status:	CLOSED ERRATA	QA Contact:	Ke Wang <kewang>
Severity:	high	Docs Contact:
Priority:	high
Version:	4.5	CC:	aos-bugs, sanchezl
Target Milestone:	---
Target Release:	4.5.z
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:	Cause: A watch cache (in Kube API) is initialized from the global revision (etcd) and might stay on it for an undefined period if no changes were (add, modify) made. Consequence: It might lead to a situation in which a client gets a resource version (RV) 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. Fix: Fix the reflector so that it can recover from "Too large resource version" errors Result: Operators that use client-go library for getting notifications from the server can recover and make progress upon receiving "Too large resource version" error	Story Points:	---
Clone Of:
Clones:	1881819 1893637 (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, 1881819
Bug Blocks:	1879901

Description Lukasz Szaszkiewicz 2020-09-18 10:00:07 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-storage-version-migrator-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 3 Ke Wang 2020-09-27 06:44:27 UTC

- cluster-kube-storage-version-migrator-operator checking, as expected version.so move the bug verified.

$ git clone https://github.com/openshift/cluster-kube-storage-version-migrator-operator.git

$ cd cluster-kube-storage-version-migrator-operator

$ oc adm release info --commits registry.svc.ci.openshift.org/ocp/release:4.5.0-0.nightly-2020-09-26-194704 | grep cluster-kube-storage-version-migrator-operator
  cluster-kube-storage-version-migrator-operator  https://github.com/openshift/cluster-kube-storage-version-migrator-operator   e0ca98802ac9c5b6a76ed039bf91fa17187c4286

$ $ git checkout -b 4.5.0-0.nightly-2020-09-26-194704 e0ca9880
Switched to a new branch '4.5.0-0.nightly-2020-09-26-194704'

$ grep -i 'k8s.io/client-go v' go.mod
	k8s.io/client-go v0.18.6

Comment 6 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