Hi!
I have a question about the impact of the max_fails and fail_timeout settings to the error pages which nginx is showing.

First, the God created an upstream:
upstream my_upstream {
server 192.168.104.58:81 max_fails=2 fail_timeout=30m;
server 192.168.104.58:82 max_fails=2 fail_timeout=30m;
}


I'm just checking the nginx behaviour to know what error pages will it display in case of different errors, so on the upstream server I have firewalled connections to the port 81 and 82 by iptables -I INPUT -p tcp --dport 81 -j DROP (and the same for port 82)

Testing:
a) First request - after timeout for backends Nginx's giving 504 error page (gateway timeout) which is correct (and it's 1st FAIL for max_fails)
b) Second request - as above, after timeout Nginx's giving 504 error page (2nd FAIL so the max_fails limit is reached) which is also correct
c) Third request - All backends are in fail state, so Nginx immediately gives 502 error page (bad gateway)

And here my doubts begin. With 4th,5th,6th, etc requests I thought I will be getting 502's unless the 30 minutes fail_timeout will end. And instead of that what I see is that Nginx's is resetting the max_fails value if all servers in upstream clause have reached the max_fails.

What I wanted to ask is if this a proper behaviour?
I think that there should be an another configuration parameter which would tell nginx what to do in such cases.

For me it's quite logical that nginx's resets this value, so it can try to check if the backend/upstream server is alive, instead of giving 502's for 30 minutes fail_timeout, but the world is big, and I think there are people that would like Nginx to throw 502's for fail_timeout period. What do you think about that ?


Best regards,
Rafal Sawer - satisfied Nginx user :)