How to upload a file through my Api connector using multipart/form-data request in Logic App?

Question

Hi,

I have a custom Api connector that I am trying to use in a Logic App to upload a *.mpp file into my endpoint. I keep getting an internal 500 error when submitting my PUT request.

To explain my Logic App, I have a reoccurrence trigger that is followed by an action to get the file content from my *.mpp file in OneDrive. Then, that content is stored in a temporary blob. Followed by the get blob content action so I can input that into my API. (I saw a lot of people used temporary blobs for file uploads)

I have ensured that the file can upload, I know I also noticed that some characters were corrupted so I had to mess around to fix that issue to preserve data. So, I'm really stuck on how to pass this file in my multipart/form-data request.

My API is using a multipart/form-data content type for the upload. Here's a snippet of my PUT request in my Logic App. I would love to use a connector rather than just using individual http actions in my app since I'm using OAuth credentials that utilize refresh tokens.

{
    "inputs": {
        "host": {
            "connection": {
                "name": "@parameters('$connections')['Name_of_Connection']['connectionId']"
            }
        },
        "method": "put",
        "headers": {
            "Company-Id": 00000
        },
        "path": "/rest/v1.0/schedule_integration",
        "queries": {
            "project_id": 00000
        },
        "body": {
            "$content-type": "multipart/form-data",
            "$multipart": [
                {
                    "headers": {
                        "Content-Disposition": "form-data; name=\"schedule_integration\"; filename=\"file.mpp\""
                    },
                    "body": "@body('Get_blob_content_(V2)')"
                }
            ]
        }
    },
    "operationOptions": "DisableAsyncPattern",
    "runtimeConfiguration": {
        "staticResult": {
            "name": "name",
            "staticResultOptions": "Disabled"
        }
    }
}

Answer 1

The initial body as part of the inputs seems off to me, unless your API is looking for $multipart parameter as part of the request. I suggest using a tool like Fiddler to observe how the traffic from the request is hitting your API. Also review Create a custom connector from a Postman collection | Microsoft Learn if you haven't done so already. Use Postman to draft your request and import the request to your custom connector. I think this will give you a better framework to craft your connection. I don't see anything wrong with @body('Get_blob_content_(V2)') but just in case, you can also append .value() to be more explicit if you're not seeing contents in the Fiddler trace.