Two Ways To Build a Recursive Logic App

Mostly everything is possible. It's always a question of how much time and energy we have. The other day I was building an Azure Logic App, and need it to make it recursive. First, I thought that couldn't be a problem because we can easily call a Logic APP from another one. This is right, nested Logic App is possible, but it's only possible to call another one. The "compilator" doesn't allow to do recursive call. I quickly found a workaround, but the day after I came to a cleaner solution.

In this post, I will share both ways to create a recursive call of a Logic App.

Commun Parts

Let's assume that our goal is to crawl a folder structure. It could be in any file connector: DroxBox, OneDrive, Google Drive, etc. For this post, I will use Sharepoint Online connector.

First, let's create our Logic App. Use the Http Request-Response template.

1. Our Logic App will receive the folder path, that it needs to process, as a parameter. This is easily done by defining a JSON schema in the Request trigger.
   

   {
       "$schema": "http://json-schema.org/draft-04/schema#",
       "properties": {
           "FolderName": {
           "type": "string"
           }
       },
       "type": "object"
   }

2. To list all the content of the current folder. Add an action List folder from the SharePoint Online connector. The File identifier should be the trigger parameter: FolderName.
   
   

   Note: You need to edit the code behind for this action. I notice a strange behavior with space in the folder path.

   
   The current code should look like this:
   

   "path": "/datasets/@{encodeURIComponent(encodeURIComponent('https://mysharepoint.sharepoint.com/sites/FrankSiteTest'))}/folders/@{encodeURIComponent(triggerBody()?['FolderName'])}" 

   
   Change it by doubling the encodeURIComponent
   

   "path": "/datasets/@{encodeURIComponent(encodeURIComponent('https://mysharepoint.sharepoint.com/sites/FrankSiteTest'))}/folders/@{encodeURIComponent(encodeURIComponent(triggerBody()?['FolderName']))}" 

3. For each element returned we need to check if it's a folder. One property of the returned object is IsFolder, we just need to use it in our condition:
   

   @equals(bool(item()?['IsFolder']), bool('True'))

   1. If it's a folder, we need to do some recursive call passing the path of the current folder to FolderName.
      
   2. Otherwise, when it's a file, do some process.

Method 1: The quick and easy

Since we are forced to call a different Logic App, let's clone our Logic App. Close the editor and click the Clone button, name it FolderCrawler2.



Now we need to edit both Logic apps by adding a call to the other one. FolderCrawler is calling FolderCrawler2 and FolderCrawler2 calls FolderCrawler.



This method is really just a workaround, but it works perfectly. What I like about it is that it uses all the Intellisense at our disposal in the editor. Obviously, the big disadvantage is the code duplication.

Method 2: The Clean and light

The real way to do a recursive call is to use the URL from the Request in an HTTP POST call. Than in the body pass a JSON matching the schema containing the Path value.



I hope you enjoy this little post. If you think of another way to do recursive call or if you have some questions, let me know!