Crash (double free or corruption) on trying to proxy to localhost

[Stephen Weeks]

Apparently these crashed don't happen with the upstreamfair module, as far
as I've been able to tell so far.  That's probably good enough as a
workaround for me for now, and may be a clue when investigating this crash.

On Sun, May 1, 2011 at 5:54 PM, Stephen Weeks <sweeks at imvu.com> wrote:

> I've currently got a pool of systems running nginx proxying to a pool of
> systems running apache.  I'm trying to move to running nginx locally on the
> apache hosts instead of separate systems to avoid the extra network hop,
> make more-efficient use of resources, and enable some future development
> (including migrating to running our application on nginx via fastcgi instead
> of apache, ideally).  we've currently got some significant architecture
> built up around apache, so converting right now is uncomfortable.
>
> Ideally, I'd like nginx to just serve from localhost, but fail over to the
> rest of the pool when localhost in unavailable, so in my upstream I have
> every server except for localhost set as 'backup'.  I'm otherwise running
> identical configurations of apache and nginx on a single system together as
> used in the rest of the two pools.  This works exactly as expected, except
> that I get a few crashes of nginx workers every minute.  This only happens
> when proxying to the local system.  If I proxy anywhere else, it works
> fine.  Other proxies can serve from this system without trouble.  I see this
> same behaviour on other hosts when I build them the same way, so it's not an
> error with the host.  I see this crash on 0.7.65, 0.8.54, and 1.0.0, running
> on Ubuntu 10.04 LTS.  I see this crash whether I'm connecting to 127.0.0.1
> or the host's local IP.  I see this crash whether I'm listening on *:80 or
> <public ip>:80.  I see this crash whether I'm connecting to :80 or running
> apache on a different port and connecting to :81.  I see this crash whether
> I'm running ubuntu's "nginx-light" configuration, or their "nginx-full"
> configuration.  I see no errors logged from apache.
>
> 1) I'd really love to make this work, so if there's anything else I can
> try, any additional debugging information I can give, I'd appreciate it.
> 2) Nginx has been very useful to me so far, so I thought you'd appreciate a
> bug report.
>
> Posted on github, I have a problem description, section of a debug log, my
> (slightly edited: flattened includes and stripped an IP) nginx.conf, a gdb
> backtrace, and some additional information I was asked for when looking for
> help on IRC.  This is everything I've been able to come up with that sounds
> plausibly relevant.
>
> https://gist.github.com/1574dbaf3a3dcda920a2
>
> Any help?
>
> (Thanks to MTechnology and kolbyjack for helping me troubleshoot this on
> IRC)
>
>
>
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