Azure Logic App Condition does not work in loop if based on changing values

Question

I need to write a simple LogicApp that connects to a http endpoint, receives some JSON, loops though the JSON message and submits it to a different http endpoint in chunks based on a value in the message.

In doing this I've come to the conclusion that Conditions inside For Each loop always evaluate the conditions before the loop and executes the path that matched the result before the loop, even though the result should have changed as the some variables have been updated in the loop.

I've managed to illustrate the problem with the below example.

{
    "definition": {
        "$schema": "https://schema.management.azure.com/providers/Microsoft.Logic/schemas/2016-06-01/workflowdefinition.json#",
        "actions": {
            "Compose": {
                "inputs": "@variables('TestStr')",
                "runAfter": {
                    "Compose_3": [
                        "Succeeded"
                    ]
                },
                "type": "Compose"
            },
            "Compose_3": {
                "inputs": "@variables('TestArray')",
                "runAfter": {
                    "For_each": [
                        "Succeeded"
                    ]
                },
                "type": "Compose"
            },
            "For_each": {
                "actions": {
                    "Compose_2": {
                        "inputs": "@variables('TestArray')",
                        "runAfter": {
                            "Condition": [
                                "Succeeded"
                            ]
                        },
                        "type": "Compose"
                    },
                    "Condition": {
                        "actions": {
                            "Append_to_array_variable": {
                                "inputs": {
                                    "name": "TestArray",
                                    "value": "@items('For_each')"
                                },
                                "runAfter": {},
                                "type": "AppendToArrayVariable"
                            },
                            "Set_variable_2": {
                                "inputs": {
                                    "name": "TestStr",
                                    "value": "XXXX"
                                },
                                "runAfter": {
                                    "Append_to_array_variable": [
                                        "Succeeded"
                                    ]
                                },
                                "type": "SetVariable"
                            }
                        },
                        "else": {
                            "actions": {
                                "Set_variable": {
                                    "inputs": {
                                        "name": "TestStr",
                                        "value": "not"
                                    },
                                    "runAfter": {},
                                    "type": "SetVariable"
                                }
                            }
                        },
                        "expression": {
                            "and": [
                                {
                                    "equals": [
                                        "@variables('TestStr')",
                                        "BlankValue"
                                    ]
                                }
                            ]
                        },
                        "runAfter": {},
                        "type": "If"
                    }
                },
                "foreach": "@variables('FullArray')",
                "runAfter": {
                    "Initialize_variable_3": [
                        "Succeeded"
                    ]
                },
                "type": "Foreach"
            },
            "Initialize_variable": {
                "inputs": {
                    "variables": [
                        {
                            "name": "TestStr",
                            "type": "String",
                            "value": "BlankValue"
                        }
                    ]
                },
                "runAfter": {},
                "type": "InitializeVariable"
            },
            "Initialize_variable_2": {
                "inputs": {
                    "variables": [
                        {
                            "name": "TestArray",
                            "type": "Array"
                        }
                    ]
                },
                "runAfter": {
                    "Initialize_variable": [
                        "Succeeded"
                    ]
                },
                "type": "InitializeVariable"
            },
            "Initialize_variable_3": {
                "inputs": {
                    "variables": [
                        {
                            "name": "FullArray",
                            "type": "Array",
                            "value": [
                                {
                                    "key": "value1"
                                },
                                {
                                    "key": "value2"
                                },
                                {
                                    "key": "value3"
                                }
                            ]
                        }
                    ]
                },
                "runAfter": {
                    "Initialize_variable_2": [
                        "Succeeded"
                    ]
                },
                "type": "InitializeVariable"
            }
        },
        "contentVersion": "1.0.0.0",
        "outputs": {},
        "parameters": {},
        "triggers": {
            "Recurrence": {
                "recurrence": {
                    "frequency": "Month",
                    "interval": 3
                },
                "type": "Recurrence"
            }
        }
    }
}

I would expect the below LogicApp to execute the loop three times, every time evaluate the condition and execute array insert only once, with the TestArray containing one entry of

{
  "key":"value1"
}

and string TestStr having value of 'not'

But the actual results seem to differ - TestArray contains all three entries from FullArray and TestStr is 'XXXX'

What am I missing here? Are there any workarounds?

Toms Jansons Toms Jansons · Accepted Answer · 2019-05-15T12:53:41

I've discovered the reason for this behaviour. Posting here if anyone comes across this in the future.

For_each loops are executed in parallel by default. That is why the conditions are evaluated for all iterations before the loop starts.

There is a way of switching this off - in the Settings you can switch on concurrency control and set parallelism to 1

Azure Logic App Condition does not work in loop if based on changing values

1 Answers