"502 Bad Gateway" on first request in a setup with Apache 2.4-servers as upstreams

maltris nginx-forum at forum.nginx.org
Fri Jul 15 17:22:16 UTC 2016

The error I am getting in the logs:

"upstream prematurely closed connection while reading response header from

After the first request it works for 10-15 seconds without any problem. 
According to tcpdump in the first request (the failing one) the upstream is
receiving one GET and nothing more.

I found one workaround
which is adding the same upstream twice and adding the "backup"-option. The
first request then fails but the second in all of my cases succeeds (checked
via logs and tcpdump).

Any ideas (also some comments that could lead me to the solution would be

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,268306,268306#msg-268306

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