is it possible to write an iRule redirecting http requrest based on URI, but doesn't require http/fasthttp profile support?

You could do something close with just a TCP profile. Something like:

 
 when CLIENT_ACCEPTED { 
   TCP::collect 
 } 
 when CLIENT_DATA { 
   set idx [string first " HTTP/1." [TCP::payload]] 
   if { $idx < 0 } { 
     if { [TCP::payload length] > 2048 } { 
        log local0. "ERROR! Could not find HTTP request in 2K! dropping..." 
        reject 
     } else { 
        Not enough data yet; collect more 
       TCP::collect 
     } 
     return 
   } 
   set request [string tolower [TCP::payload $idx]] 
   if { $request contains " /XXXXX" } { 
     pool Pool_XXXXX 
   } else { 
     pool Pool_WWWWW 
   } 
 } 
 

I have not even tested the above to see if it compiles, much less works, but it should be a good starting point. Basically, since HTTP requests start with " HTTP/", this just collects enough TCP data to find that "HTTP/1." string, and calls everything before that the "request".

Then, since you're doing starts_with and the request variable also contains the HTTP method, you'd need to do a contains " /XXXXX". In other words, that space in the string before the /XXXXX is important. If you prefer, you can (just after the string tolower line) find the first space in request and chop off all the characters up to it. Then, request should just have the URI and you can go back to starts_with.

Makes sense?

unfortunately, after i applied this iRule to our site, the whole site is not accessible. I checked the iRule line by line, but failed to figure out while line blocked the access.

 

the client just keeps connecting and then time out....

You may need a TCP::release at the end of the iRule

thanks for nmenant's reply, after adding 'tcp::release', users CAN be guided to the default pool pool_WWWWW, but the redirection to pool_XXXXX doesn't work, sorry i'm new to iRule, and can't figure out why...anybody could give me a hand?

Try throwing some logging in place:

 
 when CLIENT_ACCEPTED { 
   TCP::collect 
 } 
 when CLIENT_DATA { 
   set idx [string first " HTTP/1." [TCP::payload]] 
   if { $idx < 0 } { 
     if { [TCP::payload length] > 2048 } { 
        log local0. "ERROR! Could not find HTTP request in 2K! dropping..." 
        reject 
     } else { 
        Not enough data yet; collect more 
       TCP::collect 
     } 
     return 
   } 
   set request [string tolower [TCP::payload $idx]] 
   log local0. "Got request: $request" 
   if { $request contains " /XXXXX" } { 
     log local0. "Sending to Pool_XXXXX" 
     pool Pool_XXXXX 
   } else { 
     log local0. "Sending to Pool_WWWWW" 
     pool Pool_WWWWW 
   } 
 } 
 

This will log the each request right before checking it, so you can see if it you're getting what you expect.

One thing that I can think of that might be happening: the request is made all lowercase, so make sure your " /XXXXX" value in the if statement is also all lowercase.

the logging will be in /var/log/ltm.