prefix based pool selection with content rewriting

Hi Marek,

As Hamish suggested, you should be able to add debug logging to the iRule to figure out what's happening and why. When the third response isn't rewritten to the server1 condition, do you see the prior request being parsed as server1?

Also, it would be more efficient to use a blank stream profile and STREAM::expression based iRule to rewrite the response content compared with having LTM buffer the response payload. You can check the STREAM::expression wiki page for details and examples: http://devcentral.f5.com/wiki/default.aspx/iRules/stream__expression

If you do stick with the HTTP::collect version of the iRule, I'd suggest you limit the payload collection to a maximum of 2Mb regardless of what the server Content-Length header is set to. If TMM collects more than 4Mb of payload it will crash:

SOL6578: TMM will crash if an iRule collects more than 4MB of data

https://support.f5.com/kb/en-us/solutions/public/6000/500/sol6578.html

The creditcard scrubber Codeshare example demonstrates a good way to limit payload collection to 4Mb:

when HTTP_RESPONSE {

   Only check responses that are a text content type (text/html, text/xml, text/plain, etc).
  if { [HTTP::header "Content-Type"] starts_with "text/" } {

     Get the content length so we can collect the data (to be processed in the HTTP_RESPONSE_DATA event)
     Limit collection to 1Mb (1048576 minus a little to spare) - See SOL6578 for details
    if { [HTTP::header exists "Content-Length"] } {
      if { [HTTP::header "Content-Length"] > 1048000 }{
         Content-Length over 1Mb so collect 1Mb
        set content_length 1048000
      } else {
         Content-Length under 1Mb so collect actual length
        set content_length [HTTP::header "Content-Length"]
      }
    } else {
       Response did not have Content-Length header, so use default of 1Mb
      set content_length 1048000
    }
     Don't collect content if Content-Length header value was 0
    if { $content_length > 0 } {
       HTTP::collect $content_length
    }
  }
}
 ...

Aaron