Blob Trigger for Python Function App in Flexible Consumption Mode

When working with Azure Functions in flexible consumption mode, developers may encounter challenges setting up a Blob Trigger for Python function apps. This article outlines the solution to ensure the Blob Trigger works as expected and provides additional resources for implementation.

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Issue Overview

The problem arises when attempting to configure a Blob Trigger for a Python function app deployed in flexible consumption mode. Despite correct deployment, the trigger may fail to activate when a blob is uploaded to the specified container. Common symptoms include:

• The Blob Trigger does not fire.
• Monitoring in Application Insights does not show any requests.
• Documentation and examples for Blob Triggers in flexible consumption mode are limited or unclear.

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Root Cause

Blob Triggers in flexible consumption mode require Event Grid-based triggers to function properly. This differs from the default Blob Trigger behavior in the standard consumption plan. Misconfiguration or reliance on outdated documentation can lead to deployment failures.

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Solution

The issue was resolved by switching to an Event Grid-based trigger for Blob storage. Below are the steps to implement the solution:

Steps to Configure Blob Trigger in Flexible Consumption Mode

• Use Event Grid for Blob Storage
  Azure Blob storage triggers rely on Event Grid notifications to function in flexible consumption mode. Follow the official documentation here: Azure Blob storage trigger for Azure Functions.
• Update Your Function Code
  Ensure your Python function app is configured to handle Event Grid events. Below is an example of the function code:

import logging
import azure.functions as func

def main(event: func.EventGridEvent):
    logging.info('Event received: %s', event.get_json())

• Configure Blob Storage and Event Grid
  • Create a Blob Storage account and enable Event Grid notifications.
  • Set up an Event Grid subscription to forward events to your Azure Function.
• Deploy Using Bicep or ARM Templates
  Below is a sample Bicep template for deploying the function app with Event Grid integration:

resource blobStorage 'Microsoft.Storage/storageAccounts@2022-09-01' = {
    name: 'myBlobStorage'
    location: 'East US'
    kind: 'StorageV2'
    sku: {
        name: 'Standard_LRS'
    }
}

resource eventGridSubscription 'Microsoft.EventGrid/eventSubscriptions@2022-06-15' = {
    name: 'myBlobEventSubscription'
    scope: blobStorage
    properties: {
        destination: {
            endpointType: 'AzureFunction'
            properties: {
                functionAppResourceId: '<FunctionAppResourceId>'
            }
        }
        filter: {
            includedEventTypes: [
                'Microsoft.Storage.BlobCreated'
            ]
        }
    }
}

• Verify Deployment
  • Upload a blob to the specified container in Blob Storage.
  • Check Application Insights for the incoming requests.

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Additional Notes

• If you are using GitHub Actions or Azure DevOps for deployment, ensure the correct settings for flexible consumption mode are applied.
• For troubleshooting, refer to Azure Functions Monitoring for insights into trigger activity.

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Conclusion

The issue of configuring a Blob Trigger for Python function apps in flexible consumption mode can be resolved by utilizing Event Grid-based triggers. By following the steps outlined above, you can ensure your Blob Trigger works seamlessly with Azure Functions.

For more information, refer to the official documentation: Azure Blob storage trigger for Azure Functions.