Possable Rule crashing Unit

Have you put any logging in place to determine which part of your rules is the culprit. The one thing that sticks out at first glance is that you are using regsub to build an entire new copy of the payload which could be quite memory intensive depending on the size of your response. My guess is it's either the regsub or HTTP::payload replace but there's now way to know without some logging.

There are alternates to using regsub on the entire payload. You could use regexp with the "-indices" argument to return the indices in the source content, then call the HTTP::payload replace command for each index of matched content. This is illustrated in this post on my blog:

http://devcentral.f5.com/weblogs/joe/archive/2005/07/27/1398.aspx

Click here

The processing of the response data would look something like this:

when HTTP_RESPONSE_DATA {
  set find "http://cfwctest3.deere.com"
  set replace "https://cfwctest3.deere.com"
  set offset 0
  set diff [expr [string length $replace] - [string length $find]]
   Get indices of all instances of find string in the payload
  set indices [regexp -all -inline -nocase -indices $find [HTTP::payload]]  
  foreach idx $indices {
    set start [expr [lindex $idx 0] + $offset]
    set end [expr [lindex $idx 1] + $offset]
    set len [expr {$end - $start + 1}]
     replace the instance of find with the contents of replace
    HTTP::payload replace $start $len $replace
     modify offset if the replace string is larger or smaller
     than find.
    incr offset $diff
  }
}

But, unless the regsub or HTTP::payload replace commands are the culprit, this solution won't help you (aside from optimizing memory usage).

-Joe