Start Process Smart Service failing though Process Instance is being triggered

Question

I am triggering a Process Instance by using 'Start Process Smart Service'. A weird behavior I have noticed is, the Process Instance is being triggered but the Start Process Smart Service is crashing with an error. The target process model has just two parameters out of which one is of type CDT(single) and other is of type Date (single). I can also clearly see the triggered instances, the parameterised variables in triggered instances populated with values configured in the Start Process Smart Service node.

Content from logs is as follows:
UnattendedJavaActivityRequest] ERROR com.appiancorp.process.engine.UnattendedJavaActivityRequest - An error occurred while executing activity: id=536936184, classname=com.appiancorp.process.runtime.activities.StartProcessSmartService2
12:39:25,568 INFO [stdout] (Appian Work Item - 6406 - Proce...

chetany · Answer

Yes, the documentation does not mention the effect of chaining in target process model on the start process smart service. My theory about what is happening is as follows: The start process smart service will block (i.e not proceed further execution) until it gets the response that the process model which it targeted either started successfully or failed to start. Although the smart service is asynchronous, it needs feedback - if the process model it targetted started successfully or not. It seems that - internally the start process smart service maybe having some timeout. i.e it will wait for the response from the target process model for some pre-determined time. If it does not get any response in that time, it will timeout and crash. Activity Chaining maybe blocking longer than the internal timeout of that smart service and causing it to crash. The nature of Activity chaining is synchronous while the smart start process smart service is asynchronous. The interaction between these maybe causing it to fail. Of course this is just my theory and I could be wrong.

Dan · Answer

This is apparently a known issue on some versions of the platform and a fix will be distributed in due course, it is being tracked under - AN-74826