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From "Brian Hayward" <bhayw...@gmail.com>
Subject Re: mod proxy disabling workers after a single error
Date Sat, 05 May 2007 02:25:56 GMT
> With the following patch from trunk you are able to set retry to 0, which
> should fix your actual problem:

Thanks!

> But I think in general it is not advisable to do this at least if you are
> load balancing your backend / having a failover configuration. And even if
> you do not have such a configuration from my perspectivce it looks like to
> be important to find out why you get these connection timeouts.
> So what protocol do you speak with your backend? HTTP? What are the error
> messages you see in the error log?

BTW, I did test my patch when 1 host was down in a balancer
configuration.  It still seemed to work well.

I agree that there is a trade off for this.  If the remote system is
really slow or hung, connections can build up and overload Apache
(e.g. you run out of worker threads, run out of file descriptors,
etc).  As soon as we fix the network problem, we'll probably want to
use a higher retry value.

At this time, we lose one or two connections out of thousands.
According to the network sniffer for these connections, packets are
getting lost during the setup of the connection.  (For example - our
sniffer sees a SYN go out, get retransmitted a couple times, but the
SYN_ACK never returns for that one connection).  It could have
something todo with the HW load balancer, the NAT firewall between us
and the destination, remote web servers, or something else.  We're
still working on the analysis.

As requested, here is the error:

[Tue May 01 14:36:30 2007] [error] (145)Connection timed out: proxy:
HTTPS: attempt to connect to 1.2.3.4:443 (hostname.com) failed
[Tue May 01 14:36:30 2007] [error] ap_proxy_connect_backend disabling
worker for (hostname.com)

Thanks again for your help!
Brian

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