Logic Apps do not provide a native way to detect which specific iteration inside a foreach has failed. There’s no built-in “index tracker” for failures, and using counters can quickly become messy.
So, to solve this, we built a pattern that logs every failed iteration cleanly using only native Logic Apps features, and with a simple Design:
To better understand it, let’s break it down.
We begin our workflow Request-Response workflow with a variable that will be responsible to catch our failed iterations.
Then let’s say that we receive an array like this:
[
{ "item": 0 },
{ "item": 2 },
{ "item": 3 },
{ "item": 4 },
{ "item": 5 },
{ "item": 6 },
{ "item": 0 },
{ "item": 8 },
{ "item": 0 },
{ "item": 10 }
]
Instead of looping directly over the array, we use:
range(0, length(triggerBody()))
This gives us full control over the iteration index (0, 1, 2, etc).
Then all we need to do is to force the failure, and to do that we create a Scope Try and inside a Compose with the expression:
div(100, triggerBody()[items('For_each')]?['item'])
This divides by 100 the current item value.
If the value is 0, it throws a division by zero error which is exactly what we want to simulate failure scenarios.
Then we add a Scope Catch that will only be triggered if the previous scope fails, and inside Scope Catch, we log the failure in a Append to array variable using the expressions:
string(add(items('For_each'), 1))
result('Scope_Try')[0]['error']['message']
How does it work?
items(‘For_each’) – Returns the current index of the iteration inside the foreach loop, for example 0, 1, 2…
add(…, 1) – Adds 1 to the index since iterations on a foreach start on 1 and not on 0
string(…) – Converts the number into a string, to return it properly in the JSON response.
result(‘Scope_Try’)[0][‘error’][‘message’] – Retrieves the exact error message from the failed division.
At the end of the workflow we add a Response action, with the variable content as a response:
The result of this solution perfectly log which iterations failed without the need to use a counter to perform it.
{
"failedIterations": [
{
"iteration": "1",
"error": "Unable to process template language expressions in action 'Simulate_division' inputs at line '0' and column '0': 'Attempt to divide an integral or decimal value by zero in function 'div'.'."
},
{
"iteration": "7",
"error": "Unable to process template language expressions in action 'Simulate_division' inputs at line '0' and column '0': 'Attempt to divide an integral or decimal value by zero in function 'div'.'."
},
{
"iteration": "9",
"error": "Unable to process template language expressions in action 'Simulate_division' inputs at line '0' and column '0': 'Attempt to divide an integral or decimal value by zero in function 'div'.'."
}
]
}
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