How to change any occurrence of myhost.company.com to myhost-dr.company.com

The stream profile will not apply to HTTP headers but iRule commands could sort this out as you've suggested.

 

 

You can indeed use the stream profile to add text (through replacement).

 

 

HTTP Content-Length is automatically updated from v9.4.0.

 

 

Here's some sample code (note I'm searching for hostname/ not hostname so we don't get a match on hostname-dr;

 

You must assign a Stream profile (with no source or target strings specified) to the Virtual Server before you can use this iRule

when HTTP_REQUEST {
 We don’t want to rewrite requests, only responses
 STREAM::disable
 
 Prevent compressed responses from the server – not required if the 
 compression is offloaded to the BIG-IP
 HTTP::header remove Accept-Encoding
}

when HTTP_RESPONSE {
 Only modify body data if the response type is text
 if { [HTTP::header value Content-Type] contains "text" } {

 Search for instances of hostname/ and replace with hostname-dr/
 @ Is a delimiter at the start and end of each string
 STREAM::expression {@hostname/@hostname-dr/@}

 Apply and rewrite response
 STREAM::enable
 }
}