How to throw an exception in Azure Logic Apps? - exception

Question

Is it possible to throw an exception in a Logic App?
Specifically, I'm trying to throw an exception inside of a scope. Then in the run after of the scope I'd check if it failed and inspect it for errors. I tried using a terminate inside of a scope, but that terminates the entire logic app run.

Answer 1

As an updated solution we can use Terminate control, Terminate control has 3 status: Failed, Canceled, and Succeeded.

Answer 2

Quick Answer (TL;DR)
Problem: MSFT Azure logic app throwing exceptions
Workaround: Use logic app Scope element to simulate throwing exceptions
Create a scope element to use as your "try-catch" block
Force the scope element to fail with an invalid command to simulate an exception
Allow the scope element to fail naturally and that will count as an exception too
Detailed Answer
Context
MSFT Azure logic app workflows
live version as of 2020-06-14
Problem
Scenario: Developer wishes to throw an exception or use try-catch semantics in a logic app
Solution
As of this writing, the live version of the product does not support this feature. There is a workaround.
Workaround
Use logic app scope element
add a conditional statement inside the scope element
If the conditional statement meets the failure condition, force an exception with a deliberately invalid command
for example create a variable assignment with the value int('__ERROR__')
If the conditional statement does not meet the failure condition, do nothing
The rest of the logic app consists of two paths
The first path runs on the success of the scope element
The second path runs on the failure of the scope element (failed, skipped, timed out)
Example
Create a scope element as a "try-catch" block
Create a variable compose element with an invalid command
int('__ERROR__') ## this will cause the enclosing scope to fail
## the string __ERROR__ cannot be cast to integer
Respond to exit status of the Scope element enclosing your exception
See also
related SO answer about forcing exceptions https://stackoverflow.com/a/61101945/42223

Answer 3

No, there is no Action or Connector directly analogous to something like a throw in C#.
The closest you can get right now would be to do something like use another LogicApp instead of a scope from which you can return a specific status code.

Answer 4

It seems like there still is no option for this inside Logic App or its little brother Power Automate / Microsoft Flow.
The way I have come up with and have used in some flows, is I simply add an action for something I know for a fact will fail.
The simplest (and probably the cheapest as the built-in actions cost less in Logic Apps, even if we are talking fractions of a dollar here either way) is probably to initialize a variable, e.g. called ThrowException with type of integer.
Then a "Set variable" action is added wherever I want my flow to fail, where I set the value (remember it is of type integer) to any string expression. I simply use the expression string('Exception').
Simple example screenshot
Since the value is set via an expression this is still a valid template, but will fail upon runtime when the value is actually being set.
After this, simply use parallel branches, with appropriate Run After settings, as usual.