2021-09-02: Prometheus not connected to any Alertmanagers

Current Status

Each of our GKE clusters has 2 prometheus pods for scraping prometheus targets in that cluster. One of those GKE clusters (gprd-us-east1-c) lost one of its 2 pods, and it took 20 minutes for its replacement pod to reach a healthy state.

Timeline

View recent production deployment and configuration events / gcp events (internal only)

All times UTC.

2021-09-02

  • 16:44 - 1 of the 2 prometheus server pods dies in GKE cluster us-east1-c. A new pod is provisioned on a new k8s node, but it takes roughly 20 minutes for it to reach a healthy state. During this time, only the 1 surviving prometheus server is scraping targets in this GKE cluster and providing metrics.
  • 16:57 - @msmiley declares incident in Slack.
  • 17:05 - The replacement pod reaches a healthy state. Redundancy is restored.

This screenshot illustrates the timeline, showing when the old pod failed and when the new pod reached a healthy state:

Screenshot_from_2021-09-02_10-09-09

Corrective Actions

Corrective actions should be put here as soon as an incident is mitigated, ensure that all corrective actions mentioned in the notes below are included.

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Note: In some cases we need to redact information from public view. We only do this in a limited number of documented cases. This might include the summary, timeline or any other bits of information, laid out in out handbook page. Any of this confidential data will be in a linked issue, only visible internally. By default, all information we can share, will be public, in accordance to our transparency value.


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Incident Review
  • Ensure that the exec summary is completed at the top of the incident issue, the timeline is updated and relevant graphs are included in the summary
  • If there are any corrective action items mentioned in the notes on the incident, ensure they are listed in the "Corrective Action" section
  • Fill out relevant sections below or link to the meeting review notes that cover these topics

Customer Impact

  1. Who was impacted by this incident? (i.e. external customers, internal customers)
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  2. What was the customer experience during the incident? (i.e. preventing them from doing X, incorrect display of Y, ...)
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  3. How many customers were affected?
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  4. If a precise customer impact number is unknown, what is the estimated impact (number and ratio of failed requests, amount of traffic drop, ...)?
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What were the root causes?

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Incident Response Analysis

  1. How was the incident detected?
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  2. How could detection time be improved?
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  3. How was the root cause diagnosed?
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  4. How could time to diagnosis be improved?
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  5. How did we reach the point where we knew how to mitigate the impact?
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  6. How could time to mitigation be improved?
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  7. What went well?
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Post Incident Analysis

  1. Did we have other events in the past with the same root cause?
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  2. Do we have existing backlog items that would've prevented or greatly reduced the impact of this incident?
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  3. Was this incident triggered by a change (deployment of code or change to infrastructure)? If yes, link the issue.
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Lessons Learned

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Guidelines

Resources

  1. If the Situation Zoom room was utilised, recording will be automatically uploaded to Incident room Google Drive folder (private)
Edited by Matt Smiley