Bug 1880366 - [release 4.5] cluster-storage-operator: Fix bug in reflector not recovering from "Too large resource version"
Summary: [release 4.5] cluster-storage-operator: Fix bug in reflector not recovering ...
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: Storage
Version: 4.5
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: ---
: 4.5.z
Assignee: Jan Safranek
QA Contact: Qin Ping
URL:
Whiteboard:
Depends On: 1880369
Blocks: 1879901
TreeView+ depends on / blocked
 
Reported: 2020-09-18 11:08 UTC by Lukasz Szaszkiewicz
Modified: 2020-09-22 11:24 UTC (History)
2 users (show)

Fixed In Version:
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Last Closed: 2020-09-22 11:19:10 UTC
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Description Lukasz Szaszkiewicz 2020-09-18 11:08:42 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-storage-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 Jan Safranek 2020-09-22 11:19:10 UTC
cluster-storage-operator in 4.5.z uses client-go from kubernetes-1.12.5 (yes, that old. We rebased it in 4.6)

Comment 3 Jan Safranek 2020-09-22 11:24:18 UTC
Reading https://bugzilla.redhat.com/show_bug.cgi?id=1880309, there is no way we're updating k8s.io/client-go to 1.18.* in 4.5.z. The operator is really old, it uses "go dep", old operator-sdk and whatnot. On the positive side, it just creates one default storage class.


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