Access On-Prem files from your logic app (On-Premises Data gateway)

Accessing and reading files from On-Prem are still required in many integrations/applications, there are many ways to access them, On-Premises data gateway is one of them, it allows accessing the files on file shares or local files on the server the gateway is installed on.

For a quick guide how to setup on-prem data gateway, click here

On-Prem data gateway can be used with logic apps (function apps are not supported), for this guide, we will use a consumption logic app (this can be implemented also for standard logic apps, since on-prem data gateway’s connectors are not built-in, extra cost will be charged for your standard logic app).

Create a consumption logic app, note that the region for your logic app must match your gateway’s region, after the logic app created, select Blank Logic App, then you will be asked to select the type of the trigger for your logic app, type ‘File System’ in the search box, a list of triggers will appear, select ‘When a file is created (properties only)’

Provide the required parameters:

• Connection name: a name referring to the connection.
• The root folder can be a UNC path, or a local path on the server hosting the gateway
• Authentication Type: Windows, this is the only option for File System triggers and actions.
• A username that has permissions to access the root folder.
• The account’s password
• select the subscription underwhich the data gateway was created (your account must have access to that subscription if it is different from the subscription you are creating the logic app under).
• the gateway name.

Once you have created the connection, you can setup the trigger, make sure you have entered the correct information, you will not receive any error message if the information was not correct during creating the connection.

Now, click on the folder icon to select the folder you want the logic app to monitor for file creation, only the folder you select will be monitored, any file creation under subfolders will not trigger the logic app, if you want to monitor a subfolder, you need to create another logic app with another trigger.

If the connection parameters were wrong, you get the error shown below.

You can fix the error by going to the api conneciton under the same resource group your logic app is created in, and you can edit the connection parameters as shown in the following image.

Remember to set the interval for checking the added files, when the trigger fires, the payload is only the properties of the file(s) added to the folder being monitored

{
    "headers": {
        "Pragma": "no-cache",
        "Transfer-Encoding": "chunked",
        "Retry-After": "15",
        "Vary": "Accept-Encoding",
        "Cache-Control": "no-store, no-cache",
       ....
       ....
       ....
        "x-ms-connection-gateway-object-id": "c103d613-98cd-4062-9ac3-ef58cbf79ad6",
        "Timing-Allow-Origin": "*",
        "x-ms-apihub-cached-response": "true",
        "x-ms-apihub-obo": "false",
        "Date": "Mon, 01 Mar 2023 19:50:41 GMT",
        "Content-Type": "application/json",
        "Expires": "-1",
        "Content-Length": "381"
    },
    "body": {
        "Id": "XFx3aW4yMDE2LWRldlxTaGFyZWRcSW5cU3dlZGlzaC50eHQ=",
        "Name": "Hello.txt",
        "DisplayName": "Hello.txt",
        "Path": "\\\\win2016-dev\\Shared\\DataIn\\Hello.txt",
        "LastModified": "2023-03-01T12:20:50Z",
        "Size": 28,
        "MediaType": "text/plain",
        "IsFolder": false,
        "ETag": "\"MDUvMDEvMjAyMyAxMjoyMDo1MHwyOA==\"",
        "FileLocator": "XFx3aW4yMDE2LWRldlxTaGFyZWRcSW5cU3dlZGlzaC50eHQ=",
        "LastModifiedBy": null
    }
}

To read the content of the file added, let’s add an action under file system called ‘Get file content using path’ (or ‘Get file content’ but you provide file Id instead of the path)

If you plan to receive files with an encoding other than UTF8, it is recommended to set Infer Content Type to No, this way the connector will not predict the type of the data being read, and the file will be read as binary (application/octet-stream), you may need to stream it to a function app as base64 in terms of changing the encoding before you can use it further.

Thus, you have read the file contents from on-prem shared location, and can proceed with further actions, you may also want to delete the file at the end of the process, if so, you can use Delete file action, the following link contains full explanation of file system connectors File System – Connectors | Microsoft Learn