I use http-type check to trace health of upstreams. Sometimes module wrongly marks upstream as failed although it gets 200 OK. By checking dump I noticed the following things:
if check is marked as failed (recorded to error.log as check time out with peer) (even it gets 200 OK from remote host) then nginx sends RST immediately after getting reply
if check is marked as passed then normal session close is happened (with FIN/ACK)
if I lower number of nginx workers from auto (40) to 5-10 then false negatives become very rare
if I raise timeout from 2-3 seconds to 20-30 seconds then false negatives become very rare too
Does each nginx worker run its own checks for upstream(s) or there's one 'process' which manages these checks?
yaoweibin
commented
3 years ago
I use http-type check to trace health of upstreams. Sometimes module wrongly marks upstream as failed although it gets 200 OK. By checking dump I noticed the following things:
check time out with peer) (even it gets 200 OK from remote host) then nginx sends RST immediately after getting replyDoes each nginx worker run its own checks for upstream(s) or there's one 'process' which manages these checks?