Python function suddenly stopped working without any code or resource changes

Question

Python function suddenly stopped working without any code or resource changes

Dennis Admin 0

This durable function app runs on a Flex Consumption plan. The troubleshooting tool return the error below. There were no changes made to the code or resources. Also, the same issue occurs to the functions with the same code base in 2 other resource groups. Suspect there is a platform compatibility issue that started today. Just need help pinpointing where the compatibility issue is.

Exception Type	Total Occurrences	Exception Message	Latest Timestamp
`[Tag=''] Process reporting unhealthy: Unhealthy. Health check en`	`21`	[Tag=''] Process reporting unhealthy: Unhealthy. Health check entries are {'azure.functions.web_host.lifecycle':{'status':'Healthy','description':null},'azure.functions.script_host.lifecycle':{'status':'Unhealthy','description':'No script host available','errorCode':'NoScriptHost'},'azure.functions.webjobs.storage':{'status':'Healthy','description':null}}	5/7/2026 8:22:07 AM
`[Tag=''] Process reporting unhealthy: Unhealthy. Health check en`	`21`	[Tag=''] Process reporting unhealthy: Unhealthy. Health check entries are {'azure.functions.web_host.lifecycle':{'status':'Healthy','description':null},'azure.functions.script_host.lifecycle':{'status':'Unhealthy','description':'No script host available','errorCode':'NoScriptHost'},'azure.functions.webjobs.storage':{'status':'Healthy','description':null}}	5/7/2026 8:22:07 AM
`[Tag='azure.functions.readiness'] Process reporting unhealthy: U`	`15`	[Tag='azure.functions.readiness'] Process reporting unhealthy: Unhealthy. Health check entries are {'azure.functions.script_host.lifecycle':{'status':'Unhealthy','description':'No script host available','errorCode':'NoScriptHost'}}	5/7/2026 8:22:07 AM

Pravallika KV 14,640 Reputation points Microsoft External Staff Moderator

2026-05-07T09:41:37.5966667+00:00
Hi @Dennis Admin ,

Thanks for reaching out to Microsoft Q&A.

It looks like your Python Durable Function host isn’t coming up and in your health checks you see

“azure.functions.script_host.lifecycle”: {“status”: “Unhealthy”, “description”: “No script host available”}

That means the Functions runtime worker never actually started.

Here’s a structured way to pinpoint what’s going on:

Check host‐startup exceptions

If you have Application Insights enabled, run this query to see if the host is failing at startup:
exceptions | where customDimensions.Category == "Host.Startup"

If you’re using a Log Analytics workspace, pull your Function App console logs:
AppServiceConsoleLogs_CL | where AppName_s =~ "*<YourFunctionAppName>*" | where Log_s contains "ErrorOccuredDuringStartupOperation"

Look for errors or stack traces that indicate the Python worker crashed (e.g. WorkerProcessExitException, python exited with code 139).

Verify your runtime and Python versions

On a Flex Consumption plan, only certain Python versions and Functions runtime versions are supported.

In the Azure portal go to Configuration → General settings and confirm: • FUNCTIONS_EXTENSION_VERSION (should be ~4 for Python 3.9) • Python version (3.9 is generally the supported default right now on Flex)

If Azure rolled out an update that bumped you to a newer worker (e.g. v4 host targeting Python 3.10) and your code or native dependencies aren’t ready, the host can fail immediately.

Look for segmentation faults or native‐library issues

If your logs show a python exited with code 139, that’s typically a SIGSEGV in a C extension.

Check your requirements.txt for any unpinned packages that might have auto-upgraded overnight. Pin versions or temporarily remove suspect packages to see if the worker starts.

Confirm storage connectivity

The script host needs an AzureWebJobsStorage connection. If your storage account has new firewall rules or the connection string was rotated outside of your resources, the host can’t initialize.

Double-check that the AzureWebJobsStorage setting in Configuration is still valid and that the storage account is reachable.

Restart and redeploy

Sometimes forcing a redeploy or doing a manual restart (Platform features → Development Tools → Restart) can clear a hung worker.

If you suspect a platform bug, you can pin the host version in host.json:
{ "version": "2.0", "extensionBundle": { "id": "Microsoft.Azure.Functions.ExtensionBundle", "version": "[2.*, 3.0.0)" } }

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Python function suddenly stopped working without any code or resource changes

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