Error message, event UPDATE arrived but resourceVersions are the same - ignoring

Solution Verified - Updated -

Environment

  • Red Hat OpenShift Service Mesh
    • 2.2+

Issue

  • One of Istiod pods sometimes show the following error messages.
error ior event UPDATE arrived but resourceVersions are the same - ignoring

Resolution

  • The message is just a harmless informative message, not real error. The message notifies you that it can ignore kindly by itself.
  • Sometimes UPDATE events with the new object being equal to the old one without any real changes can be received. It can cause triggering Routes delete and recreate as always wrongly. For guarding the wrong behavior when received the events, if it's the same with old one after compairing the "resourceVersion" field of new object with old one, the error message displayed without any actual changes. As a result, the message just shows us only UPDATE event with no changes is there.
    • Refer IOR for more details of IOR component.
  • IOR is handled by one of istiod elected as a leader if you have multiple replicas of istiod pods. So the message is shown at just one istiod pod, not all pods.
// you can see the current leader pod as follows.
$ oc get cm/ior-leader -n istio-system
apiVersion: v1
kind: ConfigMap
metadata:
  annotations:
    control-plane.alpha.kubernetes.io/leader: '{"holderIdentity":"istiod-basic-xxx-xxx","holderKey":"basic","leaseDurationSeconds":30,"acquireTime":"2022-09-14T05:16:41Z","renewTime":"2022-09-16T07:50:09Z","leaderTransitions":0}'
:

Root Cause

  • The cause of UPDATE events with the new object being equal to the old one are not known unfortunately. But the events likely happen when forced the reflector to resync by dropping the WATCH on Routes or etcd leader changes at some points.

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