Cases2 cases

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1. IL-0374 DigitalOcean creates and management actions failed globally when its service discovery datastore lost quorum

   DigitalOcean2024

   Symptoms

   From 16:30 UTC on 5 August 2024, DigitalOcean's internal services could not discover the other services they depended on. Creates, event processing and the management of DigitalOcean products failed in all regions through the Cloud Control Panel and the API, while existing customer resources such as Droplets stayed online.

   Service outageCluster or node provisioning stall

   Trigger

   During the rollout of a new datastore cluster in a new datacenter, a replication configuration was deployed against the datastore behind internal service discovery that gave the new datacenter, which held zero keys, 100% ownership of all keys.

   Root cause

   Configuration change

   Component

   Coordination and key-value storeService discoveryDatabase replication

   Contributing factor

   Excessive blast radius

   Detection

   Service discovery unavailability was first reported internally at 16:35 UTC, five minutes after the rollout of the new datastore cluster began.

   Remediation

   • Reverted the replication configuration and ran it against the region that had become the datastore owner
   • Applied the configuration by hand on the nodes of lagging regions and ran local data repairs
   • Cleaned up failed events and processed pending events that had not timed out

   Action items

   • Perform this kind of datastore extension inside a declared maintenance window, announced on the status page
   • Update the process documentation for this type of deployment, stage by stage
   • Automate the manual steps used in this deployment to reduce human error
   • Evaluate the internal datastore topology and whether to regionalise or layer it

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2. IL-0473 Jenkins infrastructure went fully down after a pod IP range fix deleted every AKS node pool and could not recreate them

   Jenkins project2023

   Symptoms

   On 7 July 2023 from 11:05 to 15:25 UTC many public Jenkins infrastructure services were completely down, including get.jenkins.io, plugins.jenkins.io, accounts.jenkins.io, javadoc.jenkins.io and incrementals.jenkins.io, while ci.jenkins.io, issues.jenkins.io, repo.jenkins-ci.org and www.jenkins.io were partly or completely disrupted.

   Network unreachableResources deletedCluster or node provisioning stallService outage

   Trigger

   After the upgrade to Kubernetes 1.25 changed the range of the pods' originating IP and LDAP access was blocked, a fix (Azure PR 431) deployed at 10:55 UTC to set a proper set of pod IP ranges removed all node pools of the cluster.

   Root cause

   Configuration change

   Component

   Node poolCNI pluginCloud load balancer

   Contributing factor

   Unverified assumptionNo staged rolloutNo safeguard on destructive change

   Detection

   After the upgrade, at 10:30 UTC, the team noticed that services inside the cluster, such as accounts.jenkins.io, could not reach the LDAP service.

   Remediation

   • Created the cluster again from scratch with a fixed network setup
   • Set a custom pod CIDR in a range separate from the virtual network
   • Moved the services and their DNS records to new public IPs
   • Pushed a pull request that recorded the manual rebuild, including the IP setup, in code

   Action items

   • Protect the public IPs from deletion with a Management Lock
   • Keep the public IPs in a separate resource group and point the Kubernetes-managed load balancers to it with the service.beta.kubernetes.io/azure-load-balancer-resource-group annotation
   • Improve network diagrams and documentation so possible overlaps are visible when preparing operations
   • Avoid changing the configuration of all AKS node pools at once

   Lessons

   The team said that changing one node pool at a time would have shown the problem after the first pool and avoided a full outage, and that the public IPs should change as little as possible because users behind corporate firewalls with allow-lists depend on them. The team also noted that it could rebuild, in under 4 hours, the cluster that hosts almost all public services.

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