How to troubleshoot "functions runtime is unreachable"

Error text

This doc is intended to troubleshoot the following error when displayed in the Functions portal.

Error: Azure Functions Runtime is unreachable. Click here for details on storage configuration

Summary

This issue occurs when the Azure Functions Runtime cannot start. The most common reason for this error to occur is the function app losing access to its storage account. Read more about the storage account requirements here

Troubleshooting

We'll walk through the four most common error cases, how to identify, and how to resolve each case.

  1. Storage Account deleted
  2. Storage Account application settings deleted
  3. Storage Account credentials invalid
  4. Storage Account Inaccessible

Storage account deleted

Every function app requires a storage account to operate. If that account is deleted your Function will not work.

How to find your storage account

Start by looking up your storage account name in your Application Settings. Either AzureWebJobsStorage or WEBSITE_CONTENTAZUREFILECONNECTIONSTRING will contain the name of your storage account wrapped up in a connection string. Read more specifics at the application setting reference here

Search for your storage account in the Azure portal to see if it still exists. If it has been deleted, you will need to recreate a storage account and replace your storage connection strings. Your function code is lost and you will need to redeploy it again.

Storage account application settings deleted

In the previous step, if you did not have a storage account connection string they were likely deleted or overwritten. Deleting app settings is most commonly done when using deployment slots or Azure Resource Manager scripts to set application settings.

Required application settings

Read about these application settings here

Guidance

  • Do not check "slot setting" for any of these settings. When you swap deployment slots the Function will break.
  • Do not set these settings when using automated deployments.
  • These settings must be provided and valid at creation time. An automated deployment that does not contain these settings will result in a non-functional App, even if the settings are added after the fact.

Storage account credentials invalid

The above Storage Account connection strings must be updated if you regenerate storage keys. Read more about storage key management here

Storage account inaccessible

Your Function App must be able to access the storage account. Common issues that block a Functions access to a storage account are:

Next Steps

Now that your Function App is back and operational take a look at our quickstarts and developer references to get up and running again!