Bug 1880301

Summary: [release 4.5] cloud-credential-operator: Fix bug in reflector not recovering from "Too large resource version"
Product: OpenShift Container Platform Reporter: Lukasz Szaszkiewicz <lszaszki>
Component: Cloud Credential OperatorAssignee: Devan Goodwin <dgoodwin>
Status: CLOSED CURRENTRELEASE QA Contact: wang lin <lwan>
Severity: high Docs Contact:
Priority: high    
Version: 4.5CC: arane, lwan
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Target Release: 4.5.z   
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Last Closed: 2020-10-02 14:54:37 UTC Type: Bug
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Bug Depends On: 1880369    
Bug Blocks: 1879901    

Description Lukasz Szaszkiewicz 2020-09-18 09:13:33 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 cloud-credential-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 Akhil Rane 2020-09-30 15:03:47 UTC
we are using client-go version v0.18.6 which includes the fix. Check here -> https://github.com/openshift/cloud-credential-operator/blob/release-4.5/vendor/k8s.io/client-go/tools/cache/reflector.go#L259