Nginx - 56 day old reverse-proxy suddenly unable to connect upstream.

[bdarbro]

Sure.  "valid=3s" This probably can be relaxed, yes.  The intent was to
prevent grouping too many connections on the same 8 or so IP's we get in a
single DNS query.

> ssl_session_cache shared:SSL:1m;
> ssl_session_timeout 86400;

This is a nice pointer, thank you.  From nginx.org documentation "One
megabyte of the cache contains about 4000 sessions."  This should definitely
be higher.  Don't know if it will play into the outage I had, but good to
get this set properly going forward.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,287081,287097#msg-287097