Following my latest posts, where I talked about the new The ability to call nested Logic Apps directly from Logic Apps Designer. Let’s look at how a nested Logic App can help us overcome the current Logic Apps limitation regarding for each’ operations, in particular, the ability to add more than one action inside the loop.
📝 One-Minute Brief
This article explains how to overcome early Azure Logic Apps limitations when working with loops and ForEach actions. By using nested Logic Apps, it shows how to execute multiple actions per iteration, enabling cleaner workflows, better reuse, and more maintainable looping patterns.
Using/Implementing Looping inside Logic Apps
If you are used to working with BizTalk Server, we have certain shapes and behaviors inside BizTalk Orchestrations that we would love to have in Logic Apps, at a first glimpse, we may be surprised the lack of features/shapes to perform certain operations…however, that doesn’t mean that they are missing, most of the times we still can do those things… but in a different manner, so we may need to look the “problem” from another angle.
Looping is one of those things!
We don’t have any Looping shape, action, or operation that we can use in the Logic App Designer, similar to what we have with Conditions.
In the previous designer (v1), we had an option in the connectors, Repeat over the list, that allowed us to iterate over an array of items and run an action for each item in that list.
The current design doesn’t have this option anymore, but again, that doesn’t mean that you can’t. In this new Logic App version or designer, if it detects that the input from the previous action or trigger is an array, and if you try to use this input in a subsequent action, it will, almost every time, automatically put you on a for each operation. Which means that you are running this action for each item in that list.
Let’s look at and use the basic scenario that we are using in the last posts, were:
- The Logic Apps is triggered by a new tweet containing the hashtag we are listening.
- And then create a file.
For now, let’s ignore the dynamic creation of the file name using Azure Functions. So we have this basic Logic App.
Because each tweet will generate a new execution of this Logic App, the trigger input will be a simple single message and not an array. If we switch to code view, we will see that the Create file action will only be executed once, and it’s not inside any loop operation.
So let’s make some changes!
We will use a similar scenario, but this time we want our Logic App:
- To be triggered every hour.
- Retrieve the last 20 tweets with the hashtag #LogicApp.
- And then create a file for each tweet in our Dropbox.
For that, we will create a new Logic App called LoopingInsideLogicApps.
- Add a Recurrence trigger, and set the:
- Set the Frequency property to Hour.
- And the Interval property to 1.
- Select the plus sign, and then choose Add an action.
- From the search box, select Show Microsoft managed APIs, type Twitter, and select the Twitter – Search tweet action.
- Set the Query text property with #LogicApps hashtag.
- You can expand the action to see all the properties if you click “…” in the lower-left corner.
- And see and define the number of results you want to return.
- Select the plus sign, and then choose Add an action.
- From the search box, select Show Microsoft managed APIs, type Dropbox, and select the Dropbox – Create file action.
- Set the Folder path property, let’s say the root by typing: /.
- On the File name property, set the parameter Tweet id from the output of Search tweet action as input, followed by the string .txt.
- On the File Content property, set the parameter Tweet text from the output of the Search tweet action as input.
If we Save our Logic App, we will notice that 20 new files will be created in our Dropbox without us having defined any parameter or configuration inside the actions that would tell it to iterate over a list/array.
This happened because the designer “was smart” to understand that the input from the Search Tweet action is an array and automatically told the Create file action to work inside a for each so that it could iterate over all the items in the array.
Trying to add several actions inside a for each
Let’s say now that we want to call our Azure Function to generate the file name and create the filename in our Dropbox with it.
At first glance, we might say:
- After the Twitter – Search tweet action, we need to call our Azure Function: CreateFileName, because it doesn’t need inputs, so we set the input as an empty JSON message.
- And reconfigure the Dropbox – Create file action so that the File name property is set with the Filename parameter from the output of CreateFileName function as input.
If we once again Save our Logic App and this time, execute it manually to make it to run. You will notice that:
- The CreateFileName function is successfully executed.
- But the Create file action failed. If you see the output, you will notice that the first file was created successfully, but the following ones got the following error:
File ‘/NewTweet_6785b86d-4dda-4119-968f-c189416f22bc.txt’ already exists. Use the Update operation to update an existing file.
Maintaining the run history, but selecting the CreateFileName action to see what the output of the function was, we will notice that it was a simple output:
{
"statusCode": 200,
"headers": {
"pragma": "no-cache",
"cache-Control": "no-cache",
"date": "Wed, 20 Apr 2016 15:01:18 GMT",
"set-Cookie": "ARRAffinity=9b8e91fd330bc5b8e4bdd3e129b0412d5daca54f6c2ff8a25f773cd80fad03aa;
Path=/; Domain=functionssandromsdn.azurewebsites.net",
"server": "Microsoft-IIS/8.0",
"x-AspNet-Version": "4.0.30319",
"x-Powered-By": "ASP.NET"
},
"body": {
"FileName": "NewTweet_6785b86d-4dda-4119-968f-c189416f22bc.txt"
}
}
If we go back to our Logic App designer and switch to Code View, we will notice why this happened. By setting the input of our function to an empty JSON message, we are not telling the Logic App to iterate over the output array from the Search Tweet action and call the function to generate a different file name for each item.
Instead, if we analyze the code, we will see that the CreateFileName function is only called one time, and we will send to the connector Dropbox this same value to all the tweets.
Trying to add several actions inside a for each (second shoot)
Ok, that didn’t work well. So what if we try to force the call to the Azure Function to be inside the for each statement?
Let’s make some changes to our Logic App flow:
- First, delete the File Name property from the Dropbox – Create file action.
- Leave it empty.
- Second, let’s send a dummy JSON message to our Azure Function, forcing this action to iterate over the Search tweet output array of items by setting the following JSON message:
{ "dummy": ['Tweet text'] }
If we switch to Code view, you will notice that now this action is under a for each:
"foreach": "@body('Search_tweet')"
The problem with this approach is that
- CreateFileName action.
- And Dropbox – Create file action.
Are in two different formats for each statement and if we try to use both in the same action, for example, trying to set the Body parameter from the output CreateFileName function, we will receive the following error:
Basic workaround to solve this problem
So, one of the workarounds that you have is to modify your Azure Function, or create a new one to be able to receive one parameter:
- the twitter message
and return two parameters:
- The filename was generated.
- And the Twitter message that was passed as input.
For example:
module.exports = function (context, data) {
var Tweet = data.Tweet;
var d = new Date().getTime();
var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = (d + Math.random()*16)%16 | 0;
d = Math.floor(d/16);
return (c=='x' ? r : (r&0x3|0x8)).toString(16);
});
// Response of the function to be used later.
context.res = {
body: {
Msg: Tweet.text,
FileName: 'TweetMsg_' + uuid + ".txt"
}
};
context.done();
};
If we are using this strategy, we then need to configure the input of the function as:
{ "Text": ['Tweet text'] }
This will iterate over the list of tweets and will create another list containing all the information that we need to send to the Dropbox connector.
We then need to change all the parameters of the Dropbox – Create file action, and instead of configuring with values from the Search tweet action that will force it to iterate, we will bind it to the output provided by the Azure function output.
This will tell to this action to iterate over the function output array to create all the files in Dropbox.
Once again, if we Save our Logic App and run it, we will see that now everything will work fine.
However, in this basic workaround, we are not adding several actions to a for each statement; instead, we avoid it, go around it, and duplicate the content in another list/array… but is there another way?
How to add several actions inside a for each
Indeed, there is a better way to accomplish that, and the solution is to call another Logic App (at least until this functionality is in the design).
Still remember the Logic App that we created in my previous posts called “AddFileToDropbox” that:
- It’s triggered manually via an HTTP post, allowing it to be invoked by other Logic Apps.
- Then it will call an Azure Function to dynamically generate a filename.
- Create a Dropbox file.
- The filename is provided by the Azure Function.
- And the message content is passed in the HTTP request that triggers this Logic App.
- And finally, return an HTTP response based on the file creation status.
We will reuse this “child” Logic App in this demo now.
So what we need to do now is delete the last two actions from our current Logic App:
- Dropbox – Create file action.
- And call the CreateFileName function action.
And then call our “child” Logic App AddFileToDropbox. To accomplish that, we need:
- Select the plus sign, and then choose Add an action.
- When you select Add an Action, the search box will be presented, where all the available actions are. But now, in the search box, you can select the option: Show Logic Apps in the same region.
- And then select AddFileToDropbox.
- On the Text property, we need to set the parameter Tweet text from the output of the Search tweet action as input.
If we now Save our Logic App and run it manually, we instantly see that:
- The Search tweet action was successfully executed.
- and the AddFileToDropbox action is being executed.
We can go to our “child” Logic App to see its runs (the historic), and you probably see that some of them are already finished, and others are still running
Once all the child runs caused by the action of the parent are finished, the parent Logic App will receive the knowledge and will terminate successfully, also (if all the runs finish successfully).
How is the behavior of calling a nested Logic App inside a for each statement?
You may ask yourself how that works, it will execute on iteration one by one, in other words, in other words, will it call the child Logic App synchronously and wait for it to finish returning the response to call another one? Or it will be asynchronous?
Well, in BizTalk terms, it would be like using a Parallel Actions shape, where all the actions will be executed concurrently but independently, but the parent Logic App processing does not continue until all have completed. The parent Logic App, in this case, will receive an array containing all the responses of the child executions.
Explore more on: Tracking Message Properties
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Hi team,
I need help for logic app…how to use break condition in for each loop using logic app designer.(inside the for each loop i’m going to use IF condition once IF condition succeed then have to exit the loop at the time )…
please advise me…