Bug 1880368

Summary: [release 4.5] cluster-samples-operator: Fix bug in reflector not recovering from "Too large resource version"
Product: OpenShift Container Platform Reporter: Lukasz Szaszkiewicz <lszaszki>
Component: SamplesAssignee: Gabe Montero <gmontero>
Status: CLOSED ERRATA QA Contact: XiuJuan Wang <xiuwang>
Severity: high Docs Contact:
Priority: high    
Version: 4.5   
Target Milestone: ---   
Target Release: 4.6.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: No Doc Update
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2020-10-27 16:42:21 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, 1881068    

Description Lukasz Szaszkiewicz 2020-09-18 11:12:46 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-samples-operator and its operands are 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 Gabe Montero 2020-09-21 13:41:08 UTC 
Yeah per OCP BZ process a 4.5.z bz is going to need a 4.6 bz.  But since the problem does not exist in 4.6 
that will make BZ mechanics tricky.

I suspect the path of least resistance will be to target this bz to 4.6, mark it verified without any change, and then 
clone it for the 4.5.z work.
Comment 3 Gabe Montero 2020-09-21 13:42:21 UTC 
Confirmed 4.6 / master has the upstream k8s fix:  see https://github.com/openshift/cluster-samples-operator/blob/master/vendor/k8s.io/apimachinery/pkg/apis/meta/v1/types.go#L908
Comment 6 errata-xmlrpc 2020-10-27 16:42:21 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