From the doc: http://wiki.nginx.org/HttpUpstreamModule#server
It said when the upstream reached
fail_timeout and it will become dead. What if my server is up sometimes after?
If a upstream server failed, will nginx retry with another server in the pool?
Any variable I can configure so that they will join the pool automatically when they are up?
The documentation you linked to states that nginx will try the upstream again after
fail_timeout seconds, to see if it has come back up.
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