Blob triggers stopped working on the 1st of March 2025

Question

Blob triggers have stopped triggering a Azure function. This function has been running for over a year without issue, the last code change was weeks ago and the stop in triggering was not related to any code changes.

The Azure function App is using Consumption service plan in Windows.

The Blob triggers all continue working if the portal page for the function is loaded (just on overview). Blob triggers then continue to work for a period of time (less than 1 hour). After this blob triggers do nothing until someone opens the overview page again. Once the overview page is opened all blob triggers are rapidly processed since the last active time.

What could have changed for blob triggers to no longer be waking a Consumption function app?

Answer 1

Hi @Alex Barber,

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

The issue with blob triggers not activating your Azure function app in the Consumption plan may be due to the app going idle when there are no requests.

This can prevent triggers from firing until you access the overview page, which wakes the app and allows it to process pending events.

Additionally, there can be delays of several minutes between a blob being added or updated and the function being triggered. If you need faster response times, consider switching to a different hosting plan for more immediate trigger responses.

For further clarification, please refer to the following documentations: Document1, Document2.

I hope this information helps you understand and resolve your issue. If you have any further concerns, please feel free to reach out.

Answer 2

hi Alex, The behavior you're describing with Blob triggers not working on your Azure Function app until the overview page is opened points to a potential issue with the Consumption Plan for the Function App, along with potential configuration or platform-related changes.

Here are some possible causes and explanations for why this might be happening:

1. Consumption Plan Scaling Issues:

• Cold Start: In the Consumption Plan, Azure Functions are subject to cold starts, meaning that if there has been inactivity (no requests or triggers), the Function App might scale down to zero, and when a trigger occurs, it takes longer to scale back up.
• Scaling Delays: If the app is not getting enough events (such as Blob uploads) to scale out and be available to handle those events, it might not respond promptly when a Blob trigger occurs. The fact that the trigger starts working when you open the portal might indicate that the app is being "woken up" by some sort of management operation.

Possible Fix:

• Check Scaling and Monitor Logs: Check the scaling settings and the monitoring logs to see if there are any issues with function app scaling (such as out-of-memory or timeouts). If there is a delay in scaling, consider moving to a Premium Plan or Dedicated (App Service) Plan, which do not face the same scaling issues as the Consumption Plan.
• Keep-Alive: If this issue persists, you may want to implement a keep-alive function that periodically hits your app to prevent it from going idle, thus preventing the cold start problem.

2. App Service Plan or Platform Maintenance:

• Platform Changes or Maintenance: Azure services sometimes go through platform updates or maintenance, which can temporarily affect the performance of resources in your app. This could be a cause for blob triggers not being processed properly. A specific issue could have occurred after March 1, 2025, due to a platform update.

Possible Fix:

• Review Service Health: Check the Azure Service Health for any incidents or planned maintenance during that time that might have impacted your Function App.
• Function App Logs: Look into the Function App Logs to see if there are any errors or anomalies around the time Blob triggers stopped working. The logs might provide more insight into why the triggers are not firing.

3. Event Grid or Storage Account Configuration:

• Event Grid Delays or Misconfiguration: Azure Blob Triggers rely on Event Grid to listen for changes in the storage account. If there’s an issue with the Event Grid or if there’s a misconfiguration, it could cause a delay in triggering the function.
• Storage Account Configuration: It's also possible that there was a configuration change in your Blob Storage or Event Grid settings that could have affected how events are delivered to your Function.

Possible Fix:

• Check Event Grid Subscriptions: Verify that your Event Grid subscription to the Blob Storage account is still active and properly configured. Sometimes, Event Grid subscriptions can expire or become misconfigured, which could prevent triggers from firing.
• Check Storage Account Logs: Review the logs in your Azure Storage Account and Event Grid to ensure that events are being triggered and sent correctly to your Function App.

4. Function App Idle Timeout:

• Idle Timeout and Shutdown: In the Consumption Plan, if your function app has not received any events for some time, it might go idle. If it's idle for an extended period, it might stop receiving triggers until you manually wake it up. This might explain why the triggers work when you open the portal (this might trigger an internal process to wake up the app).

Possible Fix:

• Keep Function App Active: You can create a ping function to make periodic calls to your function, keeping it active and preventing idle shutdowns. You can also configure a heartbeat or ping function that runs at intervals to keep your function app running.

5. New Resource or Policy Changes (Post-March 2025):

• Changes After March 1, 2025: If you haven’t made any recent code changes but the issue started on a specific date (March 1, 2025), it’s possible that there was a platform update, configuration change, or resource change that impacted your Function App.

Possible Fix:

• Azure Function Settings: Check the Azure Function App Settings to see if any new settings have been applied (e.g., new resource limits, idle timeouts, etc.).
• Review Logs and Updates: Check for any platform changes or updates that were rolled out on or after March 1, 2025, which could have affected Function Apps running in the Consumption Plan.

6. Known Issue or Bug in Azure Functions:

• It's also possible that there's a known bug affecting the Consumption Plan in Azure Functions, particularly for Blob triggers. If this is the case, Azure might be working on a fix, but it might take some time.

Possible Fix:

• Azure Support: If none of the above solutions work, it might be worth reaching out to Azure Support to investigate further. They might be able to provide details if there’s a bug or a recent change that could have caused this issue.The behavior you're describing with Blob triggers not working on your Azure Function app until the overview page is opened points to a potential issue with the Consumption Plan for the Function App, along with potential configuration or platform-related changes. Here are some possible causes and explanations for why this might be happening:
  1. Consumption Plan Scaling Issues:
  • Cold Start: In the Consumption Plan, Azure Functions are subject to cold starts, meaning that if there has been inactivity (no requests or triggers), the Function App might scale down to zero, and when a trigger occurs, it takes longer to scale back up.
  • Scaling Delays: If the app is not getting enough events (such as Blob uploads) to scale out and be available to handle those events, it might not respond promptly when a Blob trigger occurs. The fact that the trigger starts working when you open the portal might indicate that the app is being "woken up" by some sort of management operation.
  Possible Fix:
  • Check Scaling and Monitor Logs: Check the scaling settings and the monitoring logs to see if there are any issues with function app scaling (such as out-of-memory or timeouts). If there is a delay in scaling, consider moving to a Premium Plan or Dedicated (App Service) Plan, which do not face the same scaling issues as the Consumption Plan.
  • Keep-Alive: If this issue persists, you may want to implement a keep-alive function that periodically hits your app to prevent it from going idle, thus preventing the cold start problem.
  2. App Service Plan or Platform Maintenance:
  • Platform Changes or Maintenance: Azure services sometimes go through platform updates or maintenance, which can temporarily affect the performance of resources in your app. This could be a cause for blob triggers not being processed properly. A specific issue could have occurred after March 1, 2025, due to a platform update.
  Possible Fix:
  • Review Service Health: Check the Azure Service Health for any incidents or planned maintenance during that time that might have impacted your Function App.
  • Function App Logs: Look into the Function App Logs to see if there are any errors or anomalies around the time Blob triggers stopped working. The logs might provide more insight into why the triggers are not firing.
  3. Event Grid or Storage Account Configuration:
  • Event Grid Delays or Misconfiguration: Azure Blob Triggers rely on Event Grid to listen for changes in the storage account. If there’s an issue with the Event Grid or if there’s a misconfiguration, it could cause a delay in triggering the function.
  • Storage Account Configuration: It's also possible that there was a configuration change in your Blob Storage or Event Grid settings that could have affected how events are delivered to your Function.
  Possible Fix:
  • Check Event Grid Subscriptions: Verify that your Event Grid subscription to the Blob Storage account is still active and properly configured. Sometimes, Event Grid subscriptions can expire or become misconfigured, which could prevent triggers from firing.
  • Check Storage Account Logs: Review the logs in your Azure Storage Account and Event Grid to ensure that events are being triggered and sent correctly to your Function App.
  4. Function App Idle Timeout:
  • Idle Timeout and Shutdown: In the Consumption Plan, if your function app has not received any events for some time, it might go idle. If it's idle for an extended period, it might stop receiving triggers until you manually wake it up. This might explain why the triggers work when you open the portal (this might trigger an internal process to wake up the app).
  Possible Fix:
  • Keep Function App Active: You can create a ping function to make periodic calls to your function, keeping it active and preventing idle shutdowns. You can also configure a heartbeat or ping function that runs at intervals to keep your function app running.
  5. New Resource or Policy Changes (Post-March 2025):
  • Changes After March 1, 2025: If you haven’t made any recent code changes but the issue started on a specific date (March 1, 2025), it’s possible that there was a platform update, configuration change, or resource change that impacted your Function App.
  Possible Fix:
  • Azure Function Settings: Check the Azure Function App Settings to see if any new settings have been applied (e.g., new resource limits, idle timeouts, etc.).
  • Review Logs and Updates: Check for any platform changes or updates that were rolled out on or after March 1, 2025, which could have affected Function Apps running in the Consumption Plan.
  6. Known Issue or Bug in Azure Functions:
  • It's also possible that there's a known bug affecting the Consumption Plan in Azure Functions, particularly for Blob triggers. If this is the case, Azure might be working on a fix, but it might take some time.
  Possible Fix:
  • Azure Support: If none of the above solutions work, it might be worth reaching out to Azure Support to investigate further. They might be able to provide details if there’s a bug or a recent change that could have caused this issue.