Re: TCP default settings (bugzilla)

plantegg ren
2026-04-17T05:58:26Z

Hi Stephen,

I'm the reporter of those two bugs. I'm a DBA and Linux SRE with over
10 years at Alibaba Cloud (Aliyun).

These come from real production pain, not just theory. During my time at
Alibaba Cloud, I pushed to change the default tcp_retries2 from 15 to 7
in Alibaba Cloud Linux 3 (ALinux3) — our in-house distro serving millions
of ECS instances. That change alone eliminated a whole class of prolonged
outages across the fleet.

The most memorable case: MySQL crashed and restarted in seconds, but the
application tier stayed down for ~16 minutes because all existing
connections were stuck in retransmission. After changing tcp_retries2 from
15 to 5, recovery time dropped from 957s to about 20s.

The tcp_keepalive_time issue bit us through LVS — connections silently
dropped after 900s of idle time, but TCP didn't notice until 7200s later.
We spent days chasing "random" Connection Reset errors across dozens of
services before tracing it to this mismatch.

Every ops team I've talked to ends up applying these tweaks independently
after getting burned. If a major cloud distro already ships tcp_retries2=7,
maybe it's time for upstream to reconsider the default too.

I did use AI to help format the bug reports (guilty as charged), but the
problems and the data are from years of production experience.

Thanks for forwarding to the list.

Xijun Ren