Microsoft Integration Product team announced this month on their monthly webcast (which you can see here) some of the new features that are now available in Logic Apps, like:
- “Run” any trigger now.
- HTTP Webhook in Designer.
- SQL Azure Connector now supports Stored Procedures.
- Azure Functions Integration and a few other features.
In my last blog posts, I talked about the new Azure Functions Integration (here and here). One of the features that they announced would soon be available was the Call nested workflow in Designer, and the good news is that it is now available to us to play.
This is a great feature that will allow us to:
- Create reusable pieces.
- Overcome some Logic Apps limitations, and what I mean by that is, for example:
- The ability to add more than one action inside the condition branch (this is actually a false statement).
- or the ability to add more than one action inside the loop.
Calling nested workflows, or Logic Apps, from another Logic App is actually not a new feature. We could previously achieve this, as you can see in this post: Using Nested Azure Logic Apps … or Invoking Flows from another Logic App. However, it was not a “first-class” experience, and we were forced to implement some workarounds to be able to achieve this goal…. Not anymore! Now it’s way simpler and with a good user experience for the designer!
📝 One-Minute Brief
This post explains how to call nested Logic Apps directly from the Logic Apps Designer, enabling reusable workflows and cleaner designs. It shows how to create parent and child Logic Apps, explains required triggers and responses, and demonstrates a practical real‑world scenario.
Creating the child Logic App
The first thing that you need to know is that, if you want to create a Logic App that you can call through another Logic App:
- The trigger of that Logic App needs to be Manual – When an HTTP request is received.
- And it should finish with a Response action.
If we don’t add the Response action in our child Logic App, what will happen is:
- The parent will call the child workflow.
- The child workflow will be executed.
- But the parent workflow will fail with the following error:
To wait on nested workflow ‘{Child Logic App Name}’, it must contain a response action.
Let’s create a simple scenario to demonstrate how we can call nested Logic Apps directly from Logic Apps Designer. In this sample, we want to create a child Logic App that:
- It’s triggered manually, which means through an HTTP post.
- In this case, let’s consider the following JSON message:
{
"Request": {
"text": "text that we want to put in file content"
}
}
- 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 content of the message is passed in the HTTP request that triggers this Logic App.
- And finally return an HTTP response based on the status of the file creation.
To accomplish that, we need:
- On the Azure Portal, click on the Logic Apps option and click Add to create a new Logic App.
- In the Create logic app panel, we need to give it:
- A Name, for example, AddFileToDropbox.
- Select the desired Subscription (if you have more than one).
- Select the desired Resource Group or create a new one.
- And finally, define the App Service Plan by choosing an existing plan or adding a new one.
- Click Create for the deployment process to start.
We have to wait a few seconds for the deployment process to finish, once it’s finished we will be notified in the notification area. You can check for more Logic Apps to create process details here.
If we select, from the Logic Apps list, the Logic App created above to open the Logic Apps Designer, we then need to:
- From the Show Microsoft management APIs option search box, click on the Manual – When an HTTP request is received trigger.
- Now, we need to give to the HTTP trigger the JSON message schema that will be sent, so that we can easily create steps.
- Unfortunately, for now, is still not possible to configure the schema directly from the designer.
- While the Product team is improving this feature, for now, we need to switch to Code view and configure the schema on the triggers > manual > inputs > schema property, which, for now, is an empty schema.
- To generate the JSON schema, we can use the JSONSchema.net online tool to easily do that task for us.
- We just need to paste our JSON message sample provided above and click Generate Schema.
- We then need to copy the JSON Schema from the website and paste it into our Logic App code view schema property.
- Now that we have set our trigger, let’s move to the next step of our Logic App.
- Select the plus sign, and then choose Add an action.
- When you select Add an Action, again, the search box will be presented, where all the connectors with their available actions are listed. But now, in the search box, you can select the option: Show Azure Functions in my subscription.
- From the search box, select Show Azure Functions in my subscription. Let’s select (if you already have it) or create a new WebHook Node function call: CreateFileName.
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: {
FileName: 'NewTweet_' + uuid + ".txt"
}
};
- This function doesn’t need any input, so we will set the “Input payload object” as an empty JSON message:
{}
- Once again, select the plus sign, and then choose Add an action.
- From the search box, type Dropbox and select the Dropbox – Create file action.
- Set the Folder path, let’s say the root by typing: /
- Note: You can also use the “…” button to navigate to your Dropbox folders.
- Click on the Filename and set the parameter Body from the output of the CreateFileName function as input.
- You don’t need to do this step, but the reason why I do it is that I am a little lazy and I want the designer to do half of the work for me.
- And then click on the File content text box, and set the parameter Text from the output of When an HTTP request is received as input.
- On top of the Logic Apps Designer, click in Code view option, for us to fix the File Name input parameter.
- Then we need to edit the Create file inputs to have the expected values
- Change the inputs > queries > name property to:
@{body('CreateFileName')['FileName']}
- Now, if we change to the Logic Apps Designer by clicking the Designer option, we will notice that the designer already renders this property and sets the expected parameter.
- Once again, select the plus sign, and then choose Add an action.
- From the search box, type Response and select the Response action.
- Set the Status Code to the value 200.
- And set the Body as “The file created was ” and the filename parameter from the output of the CreateFileName function as input.
- Save your Logic App, and we are now ready to use/call this workflow from other Logic Apps.
Creating the parent Logic App
If we now create another Logic App – the parent – let’s call it “CallNestedLogicAppDemo”.
- Add a Twitter – When a new tweet appears trigger to look for a new tweet containing the hashtag #LogicApps.
- 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.
- This will show you all the available Logic Apps that you can call from your current Logic App.
- Let’s select the AddFileToDropbox that we created earlier.
How cool is that! Yeh!
- Don’t change the Trigger name. This should be set to: Manual.
- Why? Because this is the default trigger type from your previous child Logic App.
- And the Text property we need to set the parameter Tweet text from the output of When a new tweet appears.
Once again, Save your logic app and wait to a tweet to appear, we will see that a new file was added in your Dropbox:
You can also check the runs of the Logic App to see if it runs successfully or if an error occurred, what, how long it took to run, inputs, and outputs, among others.
Unfortunately, here we don’t have similar functionality that we have on BizTalk Orchestration Debugger, the ability to View Called orchestration. It would be great to have here a similar one, View Called workflow runs.
If you want to achieve this, you need to go to the child Logic app, see the execution runs, and check if all steps are properly executed.
You can now reuse this AddFileToDropbox in several Logic Apps that you have or will create in the future.
The parent will always execute successfully because you are always returning status 200 from your child Logic App!
Well, yes indeed my last step is returning a status 200 for the parent Logic App, but this will only happen if all previous steps of the flow will be executed successfully, otherwise an error status will be received.
To put this scenario to the test, I changed the Dropbox – Create file action in my AddFileToDropbox Logic App to always create a file named Demo1.txt. I then waited for two different tweets to appear. The result:
- The first execution was executed successfully.
- And the subsequent executions failed.
With the following error:
{
"statusCode": 502,
"headers": {},
"body": {
"error": {
"code": "NoResponse",
"message": "The server did not received a response from an upstream server. Request tracking id '08587405217965861441'."
}
}
}
If we check the child execution, we will see that the Logic App is failing in the Dropbox – File Create action, and the Response action will be aborted.
Hope you find this helpful! If you liked the content or found it useful and would like to support me in writing more, consider buying (or helping to buy) a Star Wars Lego set for my son.
Great article Sandro!
Is it possible to create the equivalent to a “SOAP HTTP manual trigger” based on a WSDL using Logic Apps (to replace BizTalk orchestrations exposed as SOAP Web Services)?