Is it possible to monitor the fair proxy balancer?

[Alexander Staubo]

On Sat, Jun 28, 2008 at 2:23 AM, Robbie Allen <lists at ruby-forum.com> wrote:
> Periodically one or more of my mongrel instances will stop getting
> requests from nginx (via upstream fair).  The mongrel process is still
> running, but not getting any requests.

Our experience is that the "fair" load balancer is unstable under
heavy load, and tends to gradually pull upstreams out of the pool.
This may be what you are experiencing.

> How can I verify if nginx has taken it out of service?  Is it possible
> to get details on the current status of the fair proxy?

Not at the moment. If you want this kind of information, I recommend
HAProxy. In addition to providing machine-readable per-backend stats,
it also renders the same information as an HTML page:

  http://www.igvita.com/posts/05-08/haproxy-large.png

> I also see the following error in syslog, but I'm unsure if it is
> related....
>
> nginx[17280]: segfault at 00007fffa0869fd0 rip 00002ac509ea61e3 rsp
> 00007fffa0869ed0 error 6

That's a segment fault -- ie., Nginx is crashing on you.

Alexander.