Legacy Linux kernel defaults cap connection queues, causing 3-second API delays
Tactic · dev.to · stat: 128 cap Engineer Sergey Shinder traced hidden 3-second checkout delays during a 600,000-customer email blast to a Linux kernel mismatch. While Gunicorn requested a…
Tactic · dev.to · stat: 128 cap
Engineer Sergey Shinder traced hidden 3-second checkout delays during a 600,000-customer email blast to a Linux kernel mismatch. While Gunicorn requested a 2,048-connection backlog, Ubuntu 18.04 silently capped net.core.somaxconn at 128, dropping TCP SYN packets before server timing started. The team fixed the bottleneck by tuning sysctl parameters to 4,096.
Server APM metrics lie when queuing happens inside the kernel Audit legacy OS kernel parameters and track client-side TCP overflow metrics before scaling high-concurrency web applications.
dev.to post by Sergey Shinder
Per Sergey Shinder's post on dev.to detailing TCP connection queue debugging.
Legacy kernel defaults silently truncated TCP connection queues to a sixteenth of requested capacity, causing dropped SYN packets under load.
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