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  1. OpenShift Bugs
  2. OCPBUGS-30225

Excessive node status updates causing high control plane CPU


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      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:


      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:

            team-mco Team MCO
            openshift-crt-jira-prow OpenShift Prow Bot
            Rio Liu Rio Liu
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