HTTP request rewriting

I'm not completely familiar with ProxyPass as I'm not an Apache admin.

 

 

But if you simply want to re-write HTTP Requests so they can be passed along to an HTTP proxy server you can do it this way:

 

 

 

when HTTP_REQUEST {

 

 

Rewrite the HTTP request so that a downstream proxy server will understand it

 

HTTP::uri "http://[HTTP::host][HTTP::uri]"

 

}

 

 

 

Obviously you will have to tell it what proxy server to send the request to so you could at this point choose a pool, a specific pool member or node.

Why don't you just add a rule that does a "HTTP::header replace Location 'new value'" in the HTTP_RESPONSE event.

I've got it half way workign by rewriting the HTTP::uri before sending the request to the pool, but I still need to rewrite the response from the server.

 

 

What I haven't figured out is: I only want to rewrite the responses from the pool that contains the search devices.

 

 

For the request, the code would be:

 

 

when HTTP_REQUEST {

 

if { [ HTTP::uri ] starts_with "/search" } {

 

HTTP::uri [ findstr [HTTP::uri] "/search" 7 ]

 

pool search_pool

 

}

 

pool static_pool

 

}

 

 

and the psuedo-code for the response would be:

 

 

when HTTP_RESPONSE {

 

if { response comes from pool search_pool } {

 

rewrite the Location header

 

}

 

}

One way of accomplishing this is to store the target pool in a local variable and check that on the response.

 

 

when HTTP_REQUEST {  
   if { [ HTTP::uri ] starts_with "/search" } {  
     HTTP::uri [ findstr [HTTP::uri] "/search" 7 ]  
     pool search_pool 
     set target_pool "search_pool"  
   } 
   else { 
     pool static_pool  
     set target_pool "static_pool" 
   } 
 }

 

 

and the psuedo-code for the response would be:

 

 

when HTTP_RESPONSE {  
   if { $target_pool == "search_pool" } { 
      rewrite the location header 
   } 
 }

 

 

-Joe

Instead of saving a string, I would recommend using an integer or boolean value.

For example, instead of:

  
  set target_pool "search_pool"  
  

use:

  
  set rewrite_reponse 1  
  

and then in the response event simply do

  
  if { $rewrite_reponse } {  
  

This is quite a bit faster than string comparing when you don't need to.

I would also suggest using [string range ...] instead of the findstr as you already know that the uri starts with /search.

For example:

 
 when HTTP_REQUEST { 
    if { [HTTP::uri] starts_with "/search" } { 
       HTTP::uri [string range [HTTP::uri] 7 end] 
       pool search_pool 
       set rewrite_response 1 
    } else { 
       pool static_pool 
       set rewrite_response 0 
    } 
 } 
 

 
 when HTTP_RESPONSE { 
    if { $rewrite_response } { 
        rewrite the location header 
    } 
 } 
 

Excellent, it's working now. It wasn't celar to me that a variable set during a HTTP_REQUEST even would still be set during the HTTP_RESPONSE.

 

 

I believe I encountered a bug in HTTP::uri though. With:

 

 

if { [HTTP::uri] starts_with "/search" } {

 

HTTP::uri [string range [HTTP::uri] 7 end]

 

 

if the value of HTTP::uri is "/search", then it's set equal to an empty string. When the request goes to the server, it's not valid.

 

 

So I added:

 

 

if { [string length [HTTP::URI] == 0 ] } {

 

HTTP::uri "/"

 

}

 

 

but the value of HTTP::uri remains an empty string. It seems that once it's zeroed out, it can't be set again.

 

 

At the very least, it should still be a valid function/variable, or ideally reset to "/" when the request is sent to the server.

Try this modification to take care of your empty string problem:

 
 when HTTP_REQUEST { 
    if { [HTTP::uri] starts_with "/search" } { 
       set new_uri [string range [HTTP::uri] 7 end] 
       if { not $new_uri starts_with "/" } { 
          set new_uri "/$new_uri" 
       } 
       HTTP::uri $new_uri 
       pool search_pool 
       set rewrite_response 1 
    } else { 
       pool static_pool 
       set rewrite_response 0 
    } 
 }