Bug 1880344

Summary:	[release 4.5] cluster-machine-approver: Fix bug in reflector not recovering from "Too large resource version"
Product:	OpenShift Container Platform	Reporter:	Alberto <agarcial>
Component:	Cloud Compute	Assignee:	Joel Speed <jspeed>
Cloud Compute sub component:	Other Providers	QA Contact:	Milind Yadav <miyadav>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	high
Priority:	high	CC:	lszaszki, zhsun
Version:	4.5
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:	1880331	Environment:
Last Closed:	2020-10-26 15:11:50 UTC	Type:	---
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:	1880331
Bug Blocks:	1879901, 1880369

Description Alberto 2020-09-18 10:26:58 UTC

+++ This bug was initially created as a clone of Bug #1880331 +++

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-machine-approver 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 1 Joel Speed 2020-09-30 16:04:56 UTC

I will verify if we need to do anything for this during the next sprint

Comment 3 Milind Yadav 2020-10-15 09:05:04 UTC

VALIDATED repo version updated to use 18.9 as expected .

4.5.0-0.nightly-2020-10-15-034441 and 4.5.0-0.nightly-2020-10-14-095539 , regression results look good ....

Comment 6 errata-xmlrpc 2020-10-26 15:11:50 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 4.5.16 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-2020:4268