Re: Check if external url exists with standard Apache directives (Apache Users)

Hi Yehuda,

Thanks for your answer and... yep, I can't change the 'destination' server.

Nevertheless this is an interesting answer, because it is first one near the solution I was looking for.

Anyway, may be there is a problem with the order of execution.

I mean, as far as I read, this solution is based on an apache "load balancer" feature and I'm not sure we can define the order wherewith origin and destination servers will be used.

I must execute the first request on 'destination' server and, only if the resource is not found, I could try with 'origin'.

Just for sake of curiosity I'll try to implement it in my test env.

Thanks again for your answer,

Vincenzo

2013/5/21 Yehuda Katz <yehuda@xxxxxxxxxx>

Your question looks similar to this StackOverflow question: http://serverfault.com/questions/83099/apache2-mod-proxy-w-multiple-reverse-proxies

I am guessing from your question that you can't even change that much on the 'destination' server.
I have also looked for a way to do this and come up empty.

- Y

On Tue, May 21, 2013 at 4:17 AM, Vincenzo D'Amore <v.damore@xxxxxxxxx> wrote:

Hi all,

I'm moving a big directory of images from an HTTP server to another and I cannot change any configuration. I would like my users don't even suppose there is a moving in progress. So I thought to add a new Apache httpd server 2.2 configured as reverse proxy in front of both of those servers.

Let me say, we can call those servers 'origin' and 'destination'.
Apache when a resource does not exists in the destination should try to get it in the origin server.
I suppose to do this check, I mean if the resource exist or not in 'destination' server, using mod_rewrite, I mean RewriteCond -U option.

Actually my tentative has failed, it seems impossible check the existence of external resource using only standard apache 2.2 directives.
This is my tentative:

RewriteCond %{IS_SUBREQ} true

RewriteCond %{REQUEST_FILENAME} ^/destination
RewriteRule . http://destination-server%{REQUEST_FILENAME} [P,L]

# Check "destination" requests

RewriteCond %{IS_SUBREQ} false
RewriteCond "/destination%{REQUEST_FILENAME}" -U
RewriteRule . http://destination-server%{REQUEST_FILENAME} [P,L]

RewriteCond %{IS_SUBREQ} false
RewriteRule . http://origin-server%{REQUEST_URI} [P,L]

Is there any way to do this using mod_rewrite or some standard Apache httpd module?

Ciao,
Vincenzo

Vincenzo D'Amore
email: v.damore@xxxxxxxxx
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