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From Plüm, Rüdiger, VF-Group <ruediger.pl...@vodafone.com>
Subject Re: ping for http in mod_proxy
Date Wed, 13 Feb 2008 17:59:31 GMT
 

> -----Ursprüngliche Nachricht-----
> Von: Jim Jagielski 
> Gesendet: Mittwoch, 13. Februar 2008 18:52
> An: dev@httpd.apache.org
> Betreff: Re: ping for http in mod_proxy
> 
> 
> On Feb 13, 2008, at 12:27 PM, Plüm, Rüdiger, VF-Group wrote:
> 
> >
> >
> >> -----Ursprüngliche Nachricht-----
> >> Von: Akins, Brian
> >> Gesendet: Mittwoch, 13. Februar 2008 18:23
> >> An: dev@httpd.apache.org
> >> Betreff: Re: ping for http in mod_proxy
> >>
> >> On 2/13/08 11:07 AM, "Jim Jagielski" <jim@jaguNET.com> wrote:
> >>
> >>> I've started looking at adding "ping" support for
> >>> mod_proxy_http to complement whats in mod_proxy_ajp...
> >>> The idea is to send a simple OPTIONS * to the backend
> >>> and hope for a reply.
> >>
> >>
> >> Would it be more useful to have active healthchecking to
> >> backend servers?
> >
> > This does not help with race conditions on HTTP keepalive 
> connections.
> 
> We will never be able to completely avoid race conditions...
> whether keepalives are in place or not.

But at least the one that comes from the keepalive timer expiring on
the backend at the same time I sent the request to it. If the
backend answered to OPTIONS * on a keepalive connection it is
reasonable to assume that the keepalive timeout will not expire
until the real request hit the backend.
Regarding other races I agree, but I think the above one is the
one that is hit most frequently.


Regards

Rüdiger 

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