I've been researching performance testing the large web application I develop at my job - mainly reading The Art of Application Performance Testing and using the web. It seems the best practice for generating test scripts (i.e., the things that simulate the user) is to use a "session recorder" while someone is using the application to capture all of the HTTP requests made, and then double check that those HTTP requests can be performed again (i.e., "replayed").
The problem I have is that the application I work on is write heavy - it's basically like Google Docs. Most interactions with the application involve users creating new entities, and then working on those entities.
A typical use case is that a user logs in to the system, creates a new Google doc, and then starts adding content. The problem is that every HTTP request sent after the user creates the document must contain a reference to the ID of the document. After performing session recording it seems I'd need to go over the record and manually substitute out the specific document ID with a variable name, so that I could replay the script with multiple users simultaneously. In my application's case we could be talking about hundreds of HTTP requests that would been to be edited.
This seems like it would take a very long time. It would also make it hard to deal with changing HTTP APIs - either the script would have to be manually changed, or the whole tedious recording process would have to be repeated.
Are there best practices around dealing with this kind of situation?