Cases2 cases

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1. IL-0522 An ingress-nginx chart upgrade deleted the jenkins.io Ingress and Fastly served HTTP/503 errors for hours

   Jenkins project2021

   Symptoms

   At 11:32 UTC on 18 November 2021, a user reported in the jenkinsci/jenkins Gitter channel that https://www.jenkins.io/doc/pipeline/steps/ was answering HTTP/503 errors with the message "Guru meditation" from Fastly's varnish.

   Service outageResources deleted

   Trigger

   The ingress-nginx Helm chart was upgraded from 4.0.6 to 4.0.8 at 10:42 UTC, and the new chart added an admission webhook rule that forbids Nginx configuration blocks in Ingress annotations.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerAdmission webhookHelmCDN and edge network

   Contributing factor

   Unverified assumptionCache-masked failureMonitoring blind spotHarmful manual action

   Detection

   A user reported in the jenkinsci/jenkins Gitter channel at 11:32 UTC that a jenkins.io page answered HTTP/503 errors, and status.jenkins.io reported the incident at 11:49 UTC.

   Remediation

   • Disabled the automated systems, rolled the ingress-nginx chart back to 4.0.6 and deleted the admission webhook by hand
   • Removed the forbidden annotations from the jenkins.io configuration
   • Upgraded the jenkins.io Helm chart to the last version known to work with ingress-nginx 4.0.8
   • Redeployed the jenkins.io Helm chart through the automated system and told Fastly to drop all cached pages

   Action items

   • Always read the changelog in depth when updating the ingress controllers, with two people pairing in real time
   • Add custom Datadog monitoring for www.origin.jenkins.io so that such an outage is detected
   • Make the monitor send the Host header www.jenkins.io so it is not redirected to Fastly
   • Check a set of pages, such as the pipeline steps page, not only the front page
   • Consider an ephemeral k3s end-to-end test before deploying to production

   Lessons

   Trusting a patch version of a Helm chart for the Ingress controller without reading its changelog in depth let a new admission rule remove the jenkins.io Ingress in production. Without monitoring on origin.jenkins.io, a user found the outage. A complete staging cluster with the same DNS setup would have caught the problem before production.

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2. IL-0521 AKS pods could not mount volumes and new nodes got no CNI network interface after the cluster service principal expired

   Jenkins project2021

   Symptoms

   From 18:02 UTC on 2 June 2021, the Jenkins infrastructure AKS cluster logged errors about pods that were unable to mount volumes and about scaled-up nodes that were unable to obtain a network virtual interface from the CNI.

   Credentials unavailablePods stuck in ContainerCreating

   Trigger

   The Azure Service Principal credential of the AKS cluster expired at 17:53 UTC on 2 June 2021.

   Root cause

   Certificate or credential expiry

   Component

   Cluster cloud identityPersistent volumes and stateful setsCNI pluginNode pool

   Contributing factor

   Monitoring blind spot

   Detection

   The error behind the failures was found in the AKS UI console while the team investigated the root cause of the LTS 2.289.1 release problem.

   Remediation

   • Renewed the AKS cluster's Azure Service Principal credential, which made AKS restart all nodes automatically

   Action items

   • Add an automatic PagerDuty check that alerts a week before the service principal expires, as is done for certificates
   • Keep a team-level calendar for manual operations such as resetting a credential
   • Consider managed identities, which renew automatically, instead of the service principal

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