You can schedule your job to be run once a day, once a week, etc. So if you want it to run only once I'd change the scheduling strategy. Otherwise, once your request has been sent you may want to just stop the processor. Another option is to use a second InvokeHttp to call the NiFi REST API to stop the first InvokeHttp.
But IMO, if you are using NiFi for a one time request, once it is done, stop the processor.