not caching on stream_matched problem

I have an interesting problem I'm hoping can be solved with an iRule:

 

I have a cgi that proxies to a back-end verity cluster to retreive search results. Occasionally, (because of a problem on the verity servers) I get a bogus reply with 0 results. This ends up getting cached on WA and served to subsequent requests for the same search.

 

Here is an example of one of the bogus search results:

 

 
 { 
   "gutter_url" : "", 
   "sort_order" : "popularity", 
   "sort_by" : "album", 
   "num_results" : 0, 
   "status" : "SUCCESS", 
   "type" : "BROWSE", 
   "elapsed" : 10.086959 
 } 
 

 

 

I'd like to have rule that follows this basic logic:

 

 

1. Identify search request by uri starts_with "/search-cgi"

 

2. Look for above string '"num_results" : 0,' in response to above request.

 

3. Tell WA to not cache this response.

 

 

I have the basic shell of the iRule as follows, but it's not working: The WAM is still caching the response and serving the next request with X-Pvinfo code S10102. Another thing I cannot figure out how to do is send a no-cache header on the response so the client browser does not cache it locally.

 

 

I'd appreciate any help with this.

 

 

 
 when HTTP_REQUEST { 
   set searchreq 0 
   if { [HTTP::uri] starts_with "/search-cgi" } { 
     set searchreq 1 
     log local0. "SEARCH REQUEST: [HTTP::uri]" 
   } 
 } 
  
 when HTTP_RESPONSE { 
   STREAM::disable   
   if {$searchreq == 1} { 
      STREAM::expression {@"num_results" : 0,@} 
      STREAM::enable 
   } 
 } 
  
 when STREAM_MATCHED { 
   set badreq 1 
   log local0. "BAD SEARCH RESULT: [STREAM::match]" 
    not working for WAM: 
   CACHE::disable  
 }