How to fix function app stopped triggering on Blob Trigger?

Question

Hello! I've been using Azure Function APPs to process files uploaded into a Storage Account. 

I am using the default Storage Polling mechanism described here https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-trigger?tabs=python-v2%2Cisolated-process%2Cnodejs-v4%2Cextensionv5&pivots=programming-language-python

It does tell that it can take up to 10 minutes to detect the changes, but this is not a problem for my use case. 

I use Consumption Plan and have two Function apps written in Python and Node, both are Linux.

Lately - approximately a week both of the function apps stopped triggering completely, even though new files were being added to the storage container.

I can't see any Errors in the Logs or in Applicationinsights.

!!! Both function apps start processing straight away when I only connect to a log streaming or function app console. 

I understand the issue with the cold start and can cause delays, but not triggering completely. The times we are talking are in Days and Weeks. 

I've seen in similar issues the recommendation is to switch to a Premium plan, but that will ruin the purpose of using an event-driven system. I don't need a function app running all the time. 

Appreciate any advice or workarounds.

Answer 1

Hi ,

Thanks for reaching out to Microsoft Q&A.

Fixes i would suggest trying for blob trigger not firing in function app (consumption plan)

• Keep the function "warm" using a Timer Trigger to prevent idling.
• Reset blob trigger leases by deleting $AzureWebJobsStorage/blobtriggerlease.
• Restart the function app to refresh the host runtime.
• Ensure correct logging levels in Application Insights and check Log Streaming.
• Verify host.json settings for correct timeout and logging configurations.
• Check FUNCTIONS_EXTENSION_VERSION in application settings.
• Consider switching to Event Grid Trigger for more reliable event-driven execution.

Please feel free to click the 'Upvote' (Thumbs-up) button and 'Accept as Answer'. This helps the community by allowing others with similar queries to easily find the solution.