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1. IL-0382 Linode Object Storage in Newark and Atlanta returned 503 Slow Down to all clients under very high inbound traffic

   Linode2022

   Symptoms

   On 19 and 20 October 2022, Linode Object Storage in Newark and Atlanta slowed down, became less available and rate limited many requests with "503 - Slow Down" HTTP responses, after the clusters received extremely high inbound traffic in both request count and bandwidth.

   High error rateMemory pressure

   Trigger

   Extremely high inbound traffic, in both total requests and throughput, reached the Newark and Atlanta Object Storage clusters on 19 and 20 October 2022.

   Root cause

   Capacity exhaustion

   Component

   Object storage

   Contributing factor

   Unpatched known bugExcessive blast radius

   Remediation

   • Fixed the edge rate limiting so it enforces the advertised 750 requests per second per bucket
   • Adjusted Ceph tunables to stop runaway memory use during high-pressure storage events
   • Moved internal Object Storage components hit by resource contention to less busy, higher-performance infrastructure
   • Adjusted performance tunables on internal components and back-end clusters so customers were not rate limited too early

   Action items

   • Refine throughput and bandwidth throttling
   • Scale up the internal Object Storage infrastructure to spread load more efficiently
   • Look for further hardware performance improvements for the internal Object Storage infrastructure
   • Tune the load balancing algorithms to avoid hotspots in the clusters

   Lessons

   Linode's per-bucket rate limiting at the edge is meant to keep excess load off the back end; when it works as intended, the back-end limits, which throttle every client alike, should never come into play.

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