To call the subflow, I am using a call using a Java HTTP connector (rather than the built-in Camunda Call Activity)
That make sense, as you don’t want to wait for completion of the sub process. I wonder, why you use REST and not simply the Java API if you are in Spring boot? But this is actually a minor thing.
I want to get a message back at the START of the subflow so the main looping flow can trigger the next subflow.
Still don’t understand this. You want to have your thread back, so it should not block until the long running thing is completed?
Why exactly would a “asyncBefore=true” on the start event of the subflow not work for you?
And I try to understand if your main process needs to know when all subflows are finished?