Cases2 cases

1 to 2 of 2

1. IL-0364 A quarter of Cloud Platform ingress traffic was slow because an AWS NLB stopped health-checking targets in one zone

   UK Ministry of Justice2022

   Symptoms

   On 11 July 2022 users reported in the #ask-cloud-platform Slack channel that their applications on the Ministry of Justice Cloud Platform were slow some of the time. About 25% of ingress traffic was affected: after an AWS incident the day before, one of the three network interfaces of the 'default' ingress controllers performed slowly, and clients timed out when they tried to connect to one of the Elastic IPs of the Network Load Balancer (NLB) in front of them.

   High latencyIntermittent timeouts

   Trigger

   Some instances of the AWS NLB health checking subsystem were restarted, which set off a latent software race condition in that subsystem.

   Root cause

   Cloud provider outage

   Component

   Cloud load balancerIngress controller

   Contributing factor

   –

   Detection

   Users reported slow performance of their applications in the #ask-cloud-platform Slack channel.

   Remediation

   • AWS restarted the NLB health checking subsystem, which refreshed its list of targets and recovered the NLB in the affected Availability Zone

   Action items

   • Raised mitigation tickets after a post-incident review, filed as post-aws-incident issues in the ministryofjustice/cloud-platform repository

   View case
2. IL-0089 A test cluster deletion script run with the kube context pointing at the live-1 production cluster deleted its ingress controller, monitoring, logging, cert-manager, kiam and external-dns

   UK Ministry of Justice2020

   Symptoms

   At 18:27 on 21 September 2020 the Cloud Platform team detected that some services running on the live-1 production cluster had gone down, and some users could not reach them. The incident was declared at 18:40.

   Service outageResources deletedMonitoring outageStale endpoint routing

   Trigger

   A script for deleting a test cluster was triggered while the kube context was pointing at the live-1 production cluster instead of the test cluster.

   Root cause

   Operator error

   Component

   Ingress controllerCredential broker for podsexternal-dnsCloud load balancerPrometheus

   Contributing factor

   No safeguard on destructive change

   Detection

   The first detection was at 18:27, and the incident was declared 13 minutes later, at 18:40.

   Remediation

   • restored the default ingress controller together with external-dns and kiam, which it depends on
   • corrected the owner field in the Formbuilder Route 53 TXT records so external-dns pointed their A records at the new NLB
   • restored the remaining components with a targeted apply
   • ran the apply pipeline to restore all certificates, ServiceMonitors and Prometheus rules from the environment repository

   View case

By root cause2