Bug 1880329

Summary: [release 4.6] machine-api-operator: Fix bug in reflector not recovering from "Too large resource version"
Product: OpenShift Container Platform Reporter: Lukasz Szaszkiewicz <lszaszki>
Component: Cloud ComputeAssignee: Alberto <agarcial>
Cloud Compute sub component: Other Providers QA Contact: sunzhaohua <zhsun>
Status: CLOSED ERRATA Docs Contact:
Severity: high    
Priority: high    
Version: 4.5   
Target Milestone: ---   
Target Release: 4.6.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1880343 (view as bug list) Environment:
Last Closed: 2020-10-27 16:42:20 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:    
Bug Blocks: 1880343, 1880369    

Description Lukasz Szaszkiewicz 2020-09-18 10:02:37 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 machine-api-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 1 Alberto 2020-09-18 12:16:06 UTC 
Please lets leave this targeting 4.6. The clone for 4.5.z is https://bugzilla.redhat.com/show_bug.cgi?id=1880343 you can see that in the "Blocks" section.
Comment 3 sunzhaohua 2020-09-24 05:11:16 UTC 
Verified 
clusterversion: 4.6.0-0.nightly-2020-09-23-022756
Checking client-go for machine-api-operator,
$ git clone git:openshift/machine-api-operator.git
$ cd machine-api-operator/
$ git checkout -b 4.6.0-0.nightly-2020-09-23-022756 e0db6b
$ grep 'k8s.io/client-go' go.mod 
	k8s.io/client-go v0.19.0
this is as expected version.
Comment 6 errata-xmlrpc 2020-10-27 16:42:20 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 4.6 GA Images), 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-2020:4196