One of the common patterns we get asked about often is how to handle exceptions with a Logic App. If something fails during the flow, there are often exception policies or actions you want to make to correctly handle failures. This is a pattern we plan to make simpler and more powerful in the coming months, but for now there are ways to work with it.
First is to understand that every action within a Logic App flow has certain properties passed along with it. The most commonly accessed is @actions().outputs, where the outputs of the action are stored (e.g. the results of a SQL query). There are also more top-level attributes that are helpful in debugging and exception management. @actions().status (Succeeded, Failed, or Skipped), @actions().starttime (timestamp of when action started), and @actions().endtime (timestamp of when action completed) can all be useful.
The most common scenario is to create a log or a message whenever a failure occurs (this could be any action). At the end of your workflow you would add the step you want to be your "exception handler." In this instance I will say if a failure occurs, I want to add a message into a Service Bus Queue that will contain the status of each action within the workflow. I would add the Service Bus Queue action, and for the condition I would put:
@or(equals(actions('laststep').status, 'Failed'), equals(actions('laststep').status, 'Skipped'))
Where 'laststep' is the action ID for the last step in my workflow.
In simple terms, this condition is saying: "If the last step in my workflow fails, or if it was skipped (meaning something upstream failed), then execute this action."
We could then have the message to the queue be something like "Action 1: @{actions('step1').status}, Action 2: @{actions('step2').status}" and so on (where step1 and step2 are the action IDs of the steps in your workflow. That way if something fails, you'd have a message in a queue that you could read to find out where the failure occurred, and potentially take necessary actions. Not to mention you could expand on this to build a second Logic App that triggers whenever an item is added in the failure queue to execute a series of steps. Hopefully you get the idea.
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