Cases2 cases

1 to 2 of 2

1. IL-0244 A queued pull request destroyed the EKS subnet route table associations and Cloud Platform services went offline

   UK Ministry of Justice2024

   Symptoms

   On 20 September 2024 at 11:24 the Cloud Platform team received high priority Pingdom alerts for services on the live cluster, and from 11:26 teams reported in the #ask channel that services were unavailable. Users reported that services could not be resolved.

   Service outageNetwork unreachableResources deleted

   Trigger

   At 11:21 the infrastructure-vpc-live-1 pipeline was unpaused, and a pull request that had been waiting in its queue ran automatically.

   Root cause

   Operator error

   Component

   TerraformCI systemVPC route tables and firewall rules

   Contributing factor

   No safeguard on destructive change

   Detection

   High priority Pingdom alerts for live cluster services reached the Cloud Platform team at 11:24, and users reported that services could not be resolved.

   Remediation

   • Ran terraform apply locally to rebuild the subnet route table associations

   Action items

   • Review and update the process for pausing and resuming infrastructure pipelines so every team member knows its implications
   • Find a way to hold queued pull requests while manual infrastructure updates are under way
   • Find ways to isolate the plan and apply tasks of infrastructure pipelines better

   View case
2. IL-0091 Changing the worker node instance type through Terraform recycled all nodes at once and deleted users' production pods together

   UK Ministry of Justice2023

   Symptoms

   At 10:23 on 6 June 2023 a user of the Cloud Platform reported that all of their production pods had been deleted at the same moment. Several users received Pingdom alerts that their applications were down for a few minutes.

   Service outage

   Trigger

   The team changed the instance type of the cluster's worker nodes through Terraform.

   Root cause

   Configuration change

   Component

   Node poolTerraform

   Contributing factor

   Excessive blast radiusNo runbook

   Detection

   Users reported that their production pods had been deleted at once and that Pingdom alerts showed their applications down; the incident was declared at 11:00.

   Action items

   • Ask AWS, through a support ticket, for the steps to change the node instance type without an outage
   • Plan how to make instance type changes through Terraform without downtime and add a runbook with the steps for changing the node instance type

   View case

By root cause2