'Azure functions Error: Error "SyntaxError: Unexpected token S in JSON at position 0" occurred while parsing the response body - Service Unavailable

I am getting the error while deploying the Azure function from the local system. I wen through some blogs and it is stating that my function is unable to connect with the Azure storage account which has the functions meta data.
Also, The function on the portal is showing the error as: Azure Functions runtime is unreachable
Earlier my function was running but after integrating the function with a Azure premium App service plan it has stooped working. My assumption is that my app service plan having some restriction for the inbound/outbound traffic rule and Due to this it is unable to establish the connection with the function's associated storage account.

Also, I would like to highlight that if a function is using the premium plan then we have to add few other configuration properties.

WEBSITE_CONTENTAZUREFILECONNECTIONSTRING = "DefaultEndpointsProtocol=https;AccountName=blob_container_storage_acc;AccountKey=dummy_value==;EndpointSuffix=core.windows.net"   
WEBSITE_CONTENTSHARE = "my-function-name"

For the WEBSITE_CONTENTSHARE property I have added the function app name but I am not sure with the value.
Following is the Microsoft document reference for the function properties Microsoft Function configuration properties link

Can you please help me to resolve the issue.

Note: I am using python for the Azure functions.



Solution 1:[1]

I have created a new function app with Premium plan and selected the interpreter as Python. When we select Python, OS will be automatically Linux.

Below is the message we get to create functions for Premium plan function App:

Your app is currently in read only mode because Elastic Premium on Linux requires running from a package.

PortalScreenshot

We need to create, deploy and run function apps from a package, refer to the documentation on how we can run functions from package.

Documentation

Make sure to add all your local.settings.json configurations to Application Settings in function app.

Solution 2:[2]

Not sure of what kind of Azure Function you are using but usually when there is a Storage Account associated, we need to specify the AzureWebJobsStorage field in the serviceDependencies.json file inside Properties folder. And when I had faced the same error, the cause was that while publishing the azure function from local, some settings from the local.settings.json were missing in the Application Settings of the app service under Configuration blade.

There can be few more things which you can recheck:

  • Does the storage account you are trying to use existing still or is deleted by any chance.
  • While publishing the application from local, using the web deploy method, the publish profile is correct or has any issues.
  • Disabling the function app and then stopping the app service before redeploying it.

Hope any of the above mentions help you diagnose and solve the issue.

Solution 3:[3]

The thing is that there is a difference in how the function deployed using Consumption vs Premium service plan.

Consumption - working out of the box.

Premium - need to add the WEBSITE_RUN_FROM_PACKAGE = 1 in the function Application settings. (see https://docs.microsoft.com/en-us/azure/azure-functions/run-functions-from-deployment-package for full details)

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 SaiKarri-MT
Solution 2 Naman Sinha
Solution 3 Oren