Best way to log API calls that create records

If you have access to core code you can add logging to ~/include/api/RestService.php just below the comment that has "// This looks like the post contents are JSON".

Something like:

                    // This looks like the post contents are JSON
                    // Note: If we want to support rest based XML, we will need to change this

@$GLOBALS['log']->fatal("POSTED DATA:$postContents");

Add extra code to filter out unwanted requests based on $this->getRequest()->getRequestURI().

If it is sugarondemand then you may be able to create a ~/custom/include/api/RestService.php, derive from the core code RestService and override getRequestArgs(). I've not tried that though.

Please don't make any changes to the core files.. this is not upgrade save. Always make changes using the custom dataframework. 

I can't agree with you on this. Adding temporary logging to core code is often the only way to diagnose complex issues. Esp. SugarBPM issues (which there have been many). If OP has access to the core code then this is a quick way to prove what a client is sending.

You should be able to identify issue on SugarBPM via apache or nginx  Logs, I just create a application logichook to check when SugarBPM run and logs the bean IDs and Some parts of the arguments. Change core files are always a critical change and normally it will be overwriting. 

You should be able to identify issue on SugarBPM via apache or nginx  Logs, I just create a application logichook to check when SugarBPM run and logs the bean IDs and Some parts of the arguments. Change core files are always a critical change and normally it will be overwriting.