Azure Blob Trigger Python Function to Write To CosmosDB Error

Question

I have JSON documents being uploaded into an Azure Blob Container and I have written an Azure Python Function to write the JSON into CosmosDB. The triggering works fine, but I get an error. Here is the Python function:

import logging
import azure.functions as func

def main(myblob: func.InputStream, doc: func.Out[func.Document]):
    logging.info(f"Python blob trigger function processed blob \n"
                 f"Name: {myblob.name}\n"
                 f"Blob Size: {myblob.length} bytes")
    
    json_data = myblob.read()
    try:
        # Store output data using Cosmos DB output binding
        doc.set(func.Document.from_json(json_data))
    except Exception as e:
        logging.info(f"Error: {e}")
        print('Error:')
        print(e)

Here is the function.json file:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "name": "myblob",
      "type": "blobTrigger",
      "direction": "in",
      "path": "cloud-save-blob-container/{name}",
      "connection": "cloudsavestorage_STORAGE"
    },
    {
      "type": "cosmosDB",
      "name": "userJson",
      "databaseName": "ToDoList",
      "collectionName": "Items",
      "createIfNotExists": false,
      "connectionStringSetting": "MyCosmosDBConnectionString",
      "direction": "out"
    }
  ],
  "disabled": false
}

This the error I see in the Azure Portal:

Result: Failure Exception: FunctionLoadError: cannot load the JsonBlobTrigger1 function: the following parameters are declared in Python but not in function.json: {'doc'} Stack: File "/azure-functions-host/workers/python/3.8/LINUX/X64/azure_functions_worker/dispatcher.py", line 290, in _handle__function_load_request self._functions.add_function( File "/azure-functions-host/workers/python/3.8/LINUX/X64/azure_functions_worker/functions.py", line 112, in add_function raise FunctionLoadError(

Thanks for assistance.

Brian G Brian G · Accepted Answer · 2021-03-30T19:41:04

I have fixed the problem and my Python Function gets triggered and puts data into Cosmos DB just like I want. The problem was with my Python code. I had "doc" in two places where it should have been "userJson". One, in the "def main(...):" line and again in the "try:" block, "doc.set(...)", which didn't match the Output binding name in function.json. Once I changed the two occurrences of "doc" to "userJson" it worked.

Azure Blob Trigger Python Function to Write To CosmosDB Error

1 Answers