telemeter-client containers showing TelemeterClientFailures Warnings reporting "gateway server reported unexpected error code: 503:"

Issue

• TelemeterClientFailures Warning alerts noticed in multiple RHOCP 4.12.z & 4.13.z clusters.

  [
  {
    "labels": {
      "alertname": "TelemeterClientFailures",
      "namespace": "openshift-monitoring",
      "severity": "warning"
    },
    "annotations": {
      "description": "The telemeter client in namespace openshift-monitoring fails 900m of the requests to the telemeter service.\nCheck the logs of the telemeter-client pod with the following command:\noc logs -n openshift-monitoring deployment.apps/telemeter-client -c telemeter-client\nIf the telemeter client fails to authenticate with the telemeter service, make sure that the global pull secret is up to date, see https://docs.openshift.com/container-platform/latest/openshift_images/managing_images/using-image-pull-secrets.html#images-update-global-pull-secret_using-image-pull-secrets for more details.",
      "summary": "Telemeter client fails to send metrics"
    },
    "state": "firing",
    "activeAt": "2024-05-04T22:26:31.062424207Z",
    "value": "9e-01"
  }
  ]