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  1. OpenShift Bugs
  2. OCPBUGS-30285

Excessive node status updates causing high control plane CPU

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       * Previously, the `nodeStatusUpdateFrequency` mechanism for the Machine Config Operator (MCO) had its default value changed from `0` seconds to `10` seconds. This caused the mechanism to increase node status reporting, `nodeStatusReportFrequency`, and this impacted control plane CPU resources. Now, the `nodeStatusReportFrequency` default value is set to `5` minutes so the CPU resource issue no longer occurs.
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       * Previously, the `nodeStatusUpdateFrequency` mechanism for the Machine Config Operator (MCO) had its default value changed from `0` seconds to `10` seconds. This caused the mechanism to increase node status reporting, `nodeStatusReportFrequency`, and this impacted control plane CPU resources. Now, the `nodeStatusReportFrequency` default value is set to `5` minutes so the CPU resource issue no longer occurs.
    • Bug Fix
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      This is a clone of issue OCPBUGS-30225. The following is the description of the original issue:
      —
      This is a clone of issue OCPBUGS-29797. The following is the description of the original issue:
      —
      This is a clone of issue OCPBUGS-29713. The following is the description of the original issue:
      —
      Description of problem:

      OCPBUGS-29424 revealed that setting the node status update frequency in kubelet (introduced with OCPBUGS-15583) causes a lot of control plane CPU. 

The reason is the increased frequency of kubelet node status updates will trigger second order effects in all control plane operators that usually trigger on node changes (api server, etcd, PDB guard pod controllers, or any other static pod based machinery).

Reverting the code in OCPBUGS-15583, or manually setting the report/status frequency to 0s causes the CPU to drop immediately.

      Version-Release number of selected component (if applicable):

      any version that OCPBUGS-15583 was backported to, 4.16 down to 4.11 AFAIU

      How reproducible:

      always

      Steps to Reproduce:

      1. create a cluster that contains a fix for OCPBUGS-15583
2. observe the apiserver metrics (eg rate(apiserver_request_total[5m])), those should show abnormal values for pod/configmap GET
    alternatively the rate of node updates is increaed (rate(apiserver_request_total{resource="nodes", subresource="status", verb="PATCH"}[1m])) 

    

      Actual results:

      the node status updates every 10s, which causes high CPU usage on control plane operators and apiserver

      Expected results:

      the node status should not update that frequently, meaning the control plane CPU usage should go down again

      Additional info:

      slack thread with the node team:
https://redhat-internal.slack.com/archives/C02CZNQHGN8/p1708429189987849
    

              team-mco Team MCO
              openshift-crt-jira-prow OpenShift Prow Bot
              Sergio Regidor de la Rosa Sergio Regidor de la Rosa
              Darragh Fitzmaurice Darragh Fitzmaurice
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                Created:
                Updated:
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