Incident Library
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  1. IL-0578 Static content behind an HAProxy load balancer in an OpenStack Octavia amphora was delayed by tens of seconds
    GMO Pepabo2020
    Symptoms

    In a GMO Pepabo production setup, delivery of static content was delayed by tens of seconds. The static content was served by nginx on upstream hosts behind HAProxy, which ran as the HTTP load balancer.

    High latency
    Root cause
    Capacity exhaustion
    Component
    HAProxyLinux kernelCloud load balancer
    Contributing factor
    Unreviewed defaults
    Remediation
    • Tuned net.ipv4.tcp_mem with sysctl on the HAProxy host, which ended the delays immediately
    Lessons

    On a VM with little RAM, the boot-time default of net.ipv4.tcp_mem can be low enough to push TCP into memory pressure. TCP out of memory is not the OOM killer, and net.ipv4.tcp_mem is a system-wide limit counted in pages, unlike the per-socket net.ipv4.tcp_rmem and net.ipv4.tcp_wmem counted in bytes. The values to watch are TCP mem in /proc/net/sockstat, press in /proc/net/protocols, and TCPMemoryPressures, TCPMemoryPressuresChrono and TCPAbortOnMemory in /proc/net/netstat.

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Check your cluster for this

This case involves Cloud load balancer and HAProxy. kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

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By root cause1

Capacity exhaustion1 case

Component
Cloud load balancerHAProxyLinux kernel
Contributing factor
Unreviewed defaults
Organisation
GMO Pepabo
  1. IL-0578 Static content behind an HAProxy load balancer in an OpenStack Octavia amphora was delayed by tens of seconds
    GMO Pepabo2020