Re: [users@httpd] Reverse Proxy and SSI from Back-End Apache (Apache Users)

On 11/9/05, Devendra Singh <dee.ess@xxxxxxxxx> wrote:

On 11/9/05, Joshua Slive <jslive@xxxxxxxxx > wrote:
On 11/8/05, Devendra Singh < dee.ess@xxxxxxxxx> wrote:
> But, the problem is that when I try to access
> http://ds.india.noida/dstest.html the SSI
> /mycomps/testsuccess.html also gets parsed from the Front Apache.

Or, in other words, subrequests are not getting proxied.

Yes, SubRequests are not getting Proxied from SSI calls.

>    RewriteEngine On
>    RewriteRule \.(gif|jpg|png|txt|css|js|ico|swf)$ [OR]
>    RewriteRule !\/mycomps\/.* - [last]
>    RewriteRule ^/(.*)$ http://ds.india.noida:8080/$1 [proxy]

This looks quite bogus to me.  As far as I know, there is no [OR]
option to RewriteRule.  And you shouldn't be escaping forward slashes
in your regex.  I'm surprised this works at all.

Yes, it works. However, if I comment the line:

#RewriteRule \.(gif|jpg|png|txt|css|js|ico|swf)$ [OR]

that also suits my purpose.

About escaping of forward slashes, point noted, Thanks.

On the original problem of subrequests and proxies, I don't recall
whether or not this works correctly.  I imagine it should.

But, the original problem still remains. How do I force the subrequest due to SSI call from within a request getting served from Front Apache to go to Back Apache?

Joshua.

Thanks Joshua for your response.

But, I am still waiting for more expert hints.

DS

Problem Diagnosis -->
If I access http://ds.india.noida/mycomps/testsuccess.html directly it works okay, i.e., gets served from Back Apache:
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (2) init rewrite engine with requested uri /mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (3) applying pattern '^/mycomps/testsuccess\.html$' to uri '/mycomps/testsuccess.html'
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (3) applying pattern '^/(.*)$' to uri '/mycomps/testsuccess.html'
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (2) rewrite /mycomps/testsuccess.html -> http://ds.india.noida:8080/mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (2) forcing proxy-throughput with http://ds.india.noida:8080/mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:12:52 +051800] [ds.india.noida/sid#8e829b8][rid#8f0bf78/initial] (1) go-ahead with proxy request proxy: http://ds.india.noida:8080/mycomps/testsuccess.html [OK]

If I access http://ds.india.noida/dstest.html which has  (dstest.html has to be served from Front and /mycomps/testsuccess.html should be served from Back Apache, but both are passed through):
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida/sid#8e829b8][rid#8f16740/initial] (2) init rewrite engine with requested uri /dstest.html
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida/sid#8e829b8][rid#8f16740/initial] (3) applying pattern '^/mycomps/testsuccess\.html$' to uri '/dstest.html'
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida/sid#8e829b8][rid#8f16740/initial] (1) pass through /dstest.html
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida /sid#8e829b8][rid#8f2e908/subreq] (2) init rewrite engine with requested uri /mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida/sid#8e829b8][rid#8f2e908/subreq] (3) applying pattern '^/mycomps/testsuccess\.html$' to uri '/mycomps/testsuccess.html'
10.216.204.64 - - [09/Nov/2005:12:13:27 +051800] [ds.india.noida/sid#8e829b8][rid#8f2e908/subreq] (1) pass through /mycomps/testsuccess.html

So, the Problem is that in case of "subreq" via SSI call, the mod_rewrite.c is simply refusing to deal with a proxied subrequest (and thus SSI).

I checked the modules/mappers/mod_rewrite.c and found the following around line 1828 (httpd-2.0.55):

        /*
         * Ignore this rule on subrequests if we are explicitly
         * asked to do so or this is a proxy-throughput or a
         * forced redirect rule.
         */
        if (r->main != NULL &&
            (p->flags & RULEFLAG_IGNOREONSUBREQ ||
             p->flags & RULEFLAG_PROXY          ||
             p->flags & RULEFLAG_FORCEREDIRECT    )) {
            continue;
        }

In my opinion (of limited knowledge of Apache internals) the line with "RULEFLAG_PROXY" may be the culprit. I commented the line:

and recompiled the Front Apache. Voila, now its giving the desired effect of rewriterule on subrequest via SSI.

So, now on accessing http://ds.india.noida/dstest.html, the result is:
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida /sid#99a29b8][rid#9a2bf68/initial] (2) init rewrite engine with requested uri /dstest.html
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a2bf68/initial] (3) applying pattern '^/mycomps/.*$' to uri '/dstest.html'
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a2bf68/initial] (1) pass through /dstest.html
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (2) init rewrite engine with requested uri /mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (3) applying pattern '^/mycomps/.*$' to uri '/mycomps/testsuccess.html'
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (3) applying pattern '^/(.*)$' to uri '/mycomps/testsuccess.html'
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (2) rewrite /mycomps/testsuccess.html -> http://ds.india.noida:8080/mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (2) forcing proxy-throughput with http://ds.india.noida:8080/mycomps/testsuccess.html
10.216.204.64 - - [09/Nov/2005:12:35:53 +051800] [ds.india.noida/sid#99a29b8][rid#9a3a150/subreq] (1) go-ahead with proxy request proxy: http://ds.india.noida:8080/mycomps/testsuccess.html [OK]

I would like to seek opinion of the expert list members / developers, whether this modification is okay and would it have any bad impact somewhere else?