nginx reverse proxy proxies subset of requests slowly

anonymous_coward nginx-forum at
Tue Feb 21 06:23:35 UTC 2012

I have now done exhaustive tests on a larger instance that yields higher
throughput (>1000 #/s). The  /proc/sys/net/ipv4/tcp_syncookies setting
seems to have an effect on how much this subset of requests hang (it's
worse with the setting enabled). I'm seeing "TCP: Possible SYN flooding
on port 80. Dropping request." (or "Sending cookies") in kern.log.

Posted at Nginx Forum:,222724,222760#msg-222760

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