Cases2 cases

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1. IL-0530 Virtual router controllers in us-central1 ran out of memory in a loop, cutting networking for new and migrated VMs

   Google Cloud2023

   Symptoms

   On 5 October 2023 in us-central1, newly created VMs waited a long time before their networking worked, and VMs that had been live migrated lost connectivity for a long time after the migration. Networking telemetry showed cross-region packet loss to and from us-central1 from 03:08 US/Pacific. Health check state of VMs reached load balancers late.

   Packet lossNetwork unreachableOOMKilledStale endpoint routingCluster or node provisioning stall

   Trigger

   A management plane behaviour change, meant to decouple the processing of API updates to Instance Groups and Network Endpoint Groups used as load balancer backends, was deployed in us-central1 after rolling out to several other regions without incident.

   Root cause

   Faulty deployment

   Component

   Network control plane (SDN)Cloud load balancer

   Contributing factor

   Excessive blast radiusNo alert on limit

   Detection

   Engineers were alerted to slowness in the virtual network control plane in us-central1 at 21:45 US/Pacific on 4 October, before the packet loss started, and to controller failures from memory exhaustion at 02:11 on 5 October. Networking telemetry showed cross-region packet loss from 03:08.

   Remediation

   • Increased the memory allocated to the virtual network router controllers
   • Rolled back the management plane change in us-central1
   • Restarted by hand the routers that were still not accepting updates

   Action items

   • Alert proactively on memory risks and unexpected memory increases
   • Refactor the deployment configuration so engineers can reallocate memory much faster
   • Re-evaluate existing practices and add safety mechanisms for API reconciliation
   • Make management plane changes more visible across teams so the changes can be correlated faster
   • Adjust the deployment footprint so a regional API change is less likely to exhaust memory across the region at once
   • Optimise memory use in the traffic routers and their controllers

   View case
2. IL-0142 GKE clusters on 1.24 and later wrote unexpected fluentbit error entries such as "Failed to get record: decoder: failed to decode payload: EOF" that used up the Logging API write quota for some customers

   Google Cloud2023

   Symptoms

   From 07:13 US/Pacific on 6 July 2023, GKE customers saw unexpected additional error and warning entries in their cluster logs, written to the Cloud Logging project that holds the clusters. Standard and Autopilot clusters at GKE 1.24.x and later were affected.

   Log flood

   Trigger

   Google rolled out a new version of the GKE component that processes logs (preliminary analysis).

   Root cause

   Faulty deployment

   Component

   Telemetry agent

   Contributing factor

   –

   Remediation

   • gave customers a workaround: request a Logging API quota increase, or apply a log exclusion for the fluentbit-gke messages
   • rolled out a fix gradually to the affected clusters between 10 and 18 July 2023

   Lessons

   Log messages written by a managed logging agent count against the customer's own Logging API write quota and logging bill, so a faulty agent release can drop a customer's other logs. A log exclusion on the agent's container name and the message patterns keeps the noise out of storage until a fix arrives.

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