Handling Errors8% of the exam
On Error Continue versus On Error Propagate
Predict what a caller, an HTTP Listener and a parent flow see when an error is handled by On Error Continue (the owner succeeds with the handler's result) or On Error Propagate (the error is re-thrown), including transactions and default error logging.
Apply correct processors/syntax to implement on-error continue and on-error propagate handlers, and predict outcomes.
~7 min read · 6 practice questions ·
What the exam expects
- Write an Error Handler with
<on-error-continue>or<on-error-propagate>and predict the status code and body an HTTP Listener returns with its default responses. - Predict what a parent flow does after a Flow Reference when the referenced flow's error is continued or propagated.
- State what each On-Error component does to a transaction its owner handles.
- Explain why a handled error still appears in the log, and how to switch that off.
Key terms:
- Owner: the Flow or Try scope whose Error Handler contains the On-Error component.
- On Error Continue: runs its processors and uses their result as the owner's result, as if the owner succeeded.
- On Error Propagate: runs its processors, then re-throws the error to the next level up.
- Default responses: the HTTP Listener's 200-with-payload success response and 500-with-error-description error response.
Key facts
On Error Continue
- Detail
- Owner completes successfully with the handler's result
On Error Propagate
- Detail
- Runs, then re-throws; the owner fails
HTTP Listener default success response
- Detail
- 200 with the payload as body
HTTP Listener default error response
- Detail
- 500 with the flow error's description as body
Default handling
- Detail
- Behaves like On Error Propagate
Error in a referenced flow
- Detail
- Its own handler runs; a propagated error goes to the flow holding the Flow Reference
Flow Reference without
target- Detail
- Payload and variable changes in the referenced flow persist
Transactions
- Detail
- Continue commits, Propagate rolls back, only for a transaction the owner handles
logException- Detail
- Default
true: logs the matched error at ERROR before handling
enableNotifications- Detail
- Default
true: fires anExceptionNotification
- Why does a Flow Reference with a
targetleave the parent's payload unchanged after the referenced flow runs? - What are the HTTP Listener's default responses for success and for failure?
- What does
enableNotificationsdefault to on an On-Error component, and what does it fire? - Why does a flow with no Error Handler return the same browser result as one with On Error Propagate?
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