NonRetryableExecutorException

If you are having an exception while processing the executor that is not temporally occurred (The exceptions that have not any point of executing again), you can throw a NonRetryableExecutorException. Then the StackSaga engine will stop the execution forward, and start reverting back, according to the configuration.

IF you were unable to catch the exception properly, the execution might throw RuntimeException s. That kind of unhandled exception will be caught as non-retryable exception by the StackSaga engine as well. But if you want to have proper error handling, you have to catch exceptions properly.

Non-Retryable Executor Exceptions are allowed for the following executors.

Executor DoProcess() Method doRevert() Method

Query Executor

✔

✖

Command Executor

✔

✖

Revert Before Executor

✖

Revert After Executor

✖
You can see in the summary table, all the revert executions are not allowed NonRetryableExecutorException s. The reason for that is according to the StackSaga architecture, any command-execution can have revert execution (Compensating execution). But all the revert-executions can have retryable-exception only. Because, even though the process can be failed, the revert execution cannot be failed at all. If the process is failed, there is a revert execution to have a Compensating. But if the revert is failed, there are any other executions to have Compensating for the reverting fail.
The summary is that only forward execution can have non-retryable-exception. 
@SagaExecutor(
        executeFor = "user-service",
        liveCheck = true,
        value = "CheckUserExecutor"
)
@AllArgsConstructor
public class CheckUserExecutor implements QueryExecutor<PlaceOrderAggregator> {

    private final UserService userService;

    @Override
    public ProcessStepManager<PlaceOrderAggregator> doProcess(
            ProcessStack processStack,
            PlaceOrderAggregator aggregator,
            ProcessStepManagerUtil<PlaceOrderAggregator> stepManagerUtil
    ) throws RetryableExecutorException, NonRetryableExecutorException {

        try {

            ResponseEntity<UserDetailDto> userDetail = this.userService.getUserDetail(aggregator.getUsername());
            ...
        } catch (FeignException.ServiceUnavailable unavailableException) {
            throw RetryableExecutorException
                    .buildWith(unavailableException)
                    .build();
        } catch (FeignException.BadRequest badRequestException) {
            (1)
            throw NonRetryableExecutorException
                    .buildWith(badRequestException)
                    .put("time", LocalDateTime.now())  (2)
                    .put("reason", "BadRequest") (2)
                    ...
                    .build();
        }
    }

}
1 NonRetryableExecutorException is thrown due to the exception is a BadRequest. specially NonRetryableExecutorException provides a way to add the metadata regarding the exception.
2 Put the metadata regarding exception as a key and value.
In java, we usually pass the data regarding the exception with the exception object. But in the StackSaga it is not recommended. Because, any time any object can be serialized (even Exceptions) for saving to the event-store. Serializing an exception object (like Json or XML) is not easy, and it might be a performance issue without any benefit. And also most of the time if you pass a complex exception, it might throw an exception when it is serialized. Therefore, StackSaga engine just saves your exception as a string in the event-store(Only for seeing through the Admin-Dashboard). If you want to put some metadata to the backward regarding the exception, NonRetryableExecutorException has a method to put the data as key and value pare called put(key, value). You can put any number of key/value pare into that by using the put method.
There is nothing like you can throw an exception when some exception is occurred. If you don’t want to continue the execution of the transaction to forward, and if you decide that the transaction should be stopped at some point, due to a condition is not met, you can throw a NonRetryableExecutorException exception as well. See the full implementation