I have created a flow like
ExecuteSQL->putfile on success relation
if ExecuteSQL processor failed
I have to capture the error of ExecuteSQL processor and send email notification to user with error file
There is nothing available to the scripting processor itself to trigger output of the Error and stack trace.
What is available...
1. SiteToSiteBulletinReportingTask --- This Reporting task can be setup to send all processor produced bulletins over NiFi's S2S protocol to a target NiFi (Target could be same NiFi or NiFI cluster). You could then design a flow that filters out any bulletin with ExecuteScript in it an send that to a putEmail processor to send out a notification when any ExecuteScript processor produces a bulletin. These bulletins will not contain a stack trace if produced. But bulletin would provide necessary information on which node produced error and when that could be used to pull proper log to inspect for stack trace.
*** you may even be able to use bulletin content to parse nifi-app.log and grab the stack trace. Would need to use one of NiFi's scripting processor to do this part.
2. ScriptedReportingTask or scripted --- you may be able to build you own custom script that parses the nifi-app.log looking for ERROR log messages and capture and trailing stack trace. Then have the script send out the email notification. I am not a script writer, so not going to be very helpful here with specifics.