How to fix Azure Functions Runtime is unreachable?

Question

How to fix Azure Functions Runtime is unreachable?

Bartosz Sulima 0

Hello, I've noticed yesterday that my Azure functions from region North Europe stopped working. I use Azure API management, and when testing the endpoint it smply returns "503 Site Unavailable" with body stating "The service is unavailable.". The Function App overview page looks fine (Status: Running and all functions are "Enabled"). First issues can be spoted when I try to test specific functions (going through Function App overview page -> Function page -> "Code + Test"), instead of code I see an error "Azure Functions Runtime is unreachable.Learn more".
I've tried steps suggested here: https://learn.microsoft.com/en-us/azure/azure-functions/functions-recover-storage-account, but my storage seems just fine. I've tried to restart whole Function App, and deploy functions (I deploy using vscode), but deploy fails trying to sync triggers, as You can see below:

12:06:48 AM app-test: Deployment successful. deployer = ms-azuretools-vscode deploymentPath = Functions App ZipDeploy. Extract zip. Remote build.
12:07:03 AM app-test: Syncing triggers...
12:07:09 AM app-test: Syncing triggers (Attempt 2/6)...
12:07:21 AM app-test: Syncing triggers (Attempt 3/6)...
12:07:42 AM app-test: Syncing triggers (Attempt 4/6)...
12:08:24 AM app-test: Syncing triggers (Attempt 5/6)...
12:09:44 AM app-test: Syncing triggers (Attempt 6/6)...
12:09:46 AM: Error: Encountered an error (ServiceUnavailable) from host runtime.

I've tried deployment on Function App in other region (West Europe) and it works just fine. As far as I can tell its connected to ongoing maintenance, "Routine Planned Maintenance in Progress for App Service in North Europe", tracking id NVZH-FPZ. My concern is that it's almost 24h since the error first occured. Is there anything I can do to fix it?

navba-MSFT 27,540 Reputation points Microsoft Employee Moderator

2023-11-13T05:22:27.1466667+00:00
@Bartosz Sulima Welcome to Microsoft Q&A Forum, Thank you for posting your query here!

I understand that you are getting the error Error: Azure Functions Runtime is unreachable

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This issue occurs when the Functions runtime can't start. The most common reason for this is that the function app has lost access to its storage account.
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Action Plan:

Please ensure that the Storage account requirements are met.

Also confirm if your Function App VNET is also added in the Azure Storage Account --> Networking section as shown below:
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Could you enable All networks access to your storage account and check if that helps ?
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If you are using a new storage account, Secure the new storage account in one of the following ways:

Create a private endpoint. When using private endpoint connections, the storage account must have private endpoints for the file and blob subresources. For Durable Functions, you must also make queue and table subresources accessible through private endpoints.

Enable a service endpoint from the virtual network. When using service endpoints, enable the subnet dedicated to your function apps for storage accounts on the firewall.
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4.Ensure that the Application Settings under Configuration for the function app are correct:

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You can set the vnetrouteallenabled property to true. This indicates whether all outbound traffic from the app is routed through the virtual network. The below CLI command helps to set this:

az resource update --resource-group <group-name> --name <app-name> --resource-type "Microsoft.Web/sites" --set properties.vnetRouteAllEnabled true

Please follow the steps mentioned here, which talks about troubleshooting the runtime unreachable issue.

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Sharing a few useful articles if that helps:
https://learn.microsoft.com/en-us/azure/azure-functions/configure-networking-how-to?tabs=portal#restrict-your-storage-account-to-a-virtual-network

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Please let me know if you are still face the issue after following this.
navba-MSFT 27,540 Reputation points Microsoft Employee Moderator

2023-11-15T05:08:57.18+00:00

@Bartosz Sulima Just following up to check if the below answer helped. If that answers your query, do click "Accept the answer” for the same, which might be beneficial to other community members reading this thread. And, if you have any further query do let us know. I would be happy to help.
Bartosz Sulima 0 Reputation points

2023-11-15T22:53:01.3966667+00:00

Thank You for your answer. My network settings are already set to "enable All networks". I haven't changed anything, but tried to deploy again and it worked. I've tried my other Function App that was down before and it works just fine right now (after no actions by me). Seems like some issue out of my scope (probably connected to maintenance by MS). Please advise if I could inform the Microsoft maintenance team responsible for hanling NVZH-FPZ, that "Azure App Service application(s) may have seen a brief drop in connectivity for a few seconds", was a bit of understatement as it was fully down for hours. Thank You very much for your answer.

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navba-MSFT 27,540 Reputation points Microsoft Employee Moderator

2023-11-15T05:08:57.18+00:00

@Bartosz Sulima Just following up to check if the below answer helped. If that answers your query, do click "Accept the answer” for the same, which might be beneficial to other community members reading this thread. And, if you have any further query do let us know. I would be happy to help.
Bartosz Sulima 0 Reputation points

2023-11-15T22:53:01.3966667+00:00

Thank You for your answer. My network settings are already set to "enable All networks". I haven't changed anything, but tried to deploy again and it worked. I've tried my other Function App that was down before and it works just fine right now (after no actions by me). Seems like some issue out of my scope (probably connected to maintenance by MS). Please advise if I could inform the Microsoft maintenance team responsible for hanling NVZH-FPZ, that "Azure App Service application(s) may have seen a brief drop in connectivity for a few seconds", was a bit of understatement as it was fully down for hours. Thank You very much for your answer.

Answer 1

@Bartosz Sulima Thanks for getting back. I'm glad to hear that the issue is resolved. Thanks for posting your solution so that others experiencing the same thing can easily reference this. Since the Microsoft Q&A community has a policy that the question author cannot accept their own answer, they can only accept answers by others, I'll repost your solution in case you'd like to Accept the answer.
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Issue:
You are getting the error Error: Azure Functions Runtime is unreachable.
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Resolution:
You re-deployed your azure function app code and that fixed the issue.
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Thanks for sharing the feedback on NVZH-FPZ service health alert event. If you want the error description Azure App Service application(s) may have seen a brief drop in connectivity for a few seconds to be improvised then, I would suggest you to please share the feedback directly with our Product group team and they will take this forward:
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Here is the Link: https://feedback.azure.com/d365community/forum/3887dc70-2025-ec11-b6e6-000d3a4f09d0

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Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.

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How to fix Azure Functions Runtime is unreachable?

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