max_fails for 404s?

[Antoine Bonavita]

Hello,

>From my understanding you don't even want to set max_fails. From the
wiki (http://wiki.nginx.org/HttpUpstreamModule#server):
"max_fails = NUMBER - number of unsuccessful attempts at communicating
with the server within the time period (assigned by parameter
fail_timeout) after which it is considered inoperative"

While you hot-deploy server1 it will return 404. Because of
"proxy_next_upstream http_404", nginx will try server2 (which is
assumed to work). So, client sees response from server2.

When you're done with hot-deploying on server1, it should start
returning non-404 and you can safely hot-deploy server2.

Of course, as you are asking, this might be the configuration you
already have and it might not have this (expected) behavior. If you
have proxy_next_upstream http_404 in your configuration and it's not
working this way, you'll have to provide logs corresponding to the
hot-deployment if you want people here to give you a hand.

A.

--
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On Wed, May 18, 2011 at 9:35 PM, Steven Deobald <steven at deobald.ca> wrote:
> Hey folks,
> We've got the following scenario occurring in production. The solution is
> non-obvious... to me, at least.
> [client] ==> [nginx] ==> [service S]
> * nginx fronting 2 application servers which provide a service S. (Primary
> and backup, both running Trinidad. Trinidad is a JRuby/Rails wrapper for
> Tomcat.)
> * hot-deploying a rails (jruby) app into Trinidad causes Trinidad to return
> a 404 to nginx
> * nginx returns the 404 to the application. In this particular case, the
> client is another service which expects service S to remain live during
> deployments
> So, nginx does provide an "http_404" case for the "proxy_next_upstream"
> directive. However, this would require the "max_fails" setting to pertain to
> 404s, which it doesn't... otherwise legitimate 404s produce an infinite
> loop.
> Is there something like "max_fails" for 404s?
> Is there another solution to this problem?
> Is it Trinidad's fault for returning 404s and not 503s? (I would say it is
> but I can't find a solution to that problem just yet.)
> Thanks!
> -steven
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