Azure function not able to write files to its fileshare

Question

Hey

So I'm deploying using Visual Studio Code.
Other colleagues use Visual Studio but behavior of deployment is similar.

The function then tries to create and save information into a file. But I always run into exceptions. Not listing them here but to my understanding, it seems that the Function doesn't have read/write access to the local fileshare that is created during initial deploy of the application.

For the file and directory path I have used code like this:

string startPath = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString());

this:
string startPath = System.IO.Path.GetTempPath(); -> points to /local/temp directory that doesnt really exists when looking into the FileShare using the Azure Portal

this:
string startPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location); -> points to it's "bin" directory

even hardcoding like this:
string startPath = "C:\site\wwwroot\result"; or string startPath = "C:\home\site\wwwroot\result";

I do get different error messages, but in the end it never allows the Function to save into its local fileshare directory under "wwwroot", which is what I think it can read/write to.

Any ideas on how to enable the Function to be able to save/create files? What is the best practice when trying to use the file directory access and the correct "paths" to use?

Is it any deployment setting I need to be aware of?
Have tried playing around with the WEBSITE_RUN_FROM_PACKAGE setting, but not sure I should modify that.

Many thanks for your feedback.
Best Regards
/Antonios

Answer 1

@antonios peris ,

Thanks for reaching out to Q&A.

Every Azure Web App has a home directory stored/backed by Azure Storage. This network share is where applications store their content. This directory is available for the sandbox with read/write access. The file directory is either D:\ or C:\ , you can check this by opening the Kudu site of the function app (site is not available for Linux consumption app)

Functions Sandbox restrictions : https://github.com/projectkudu/kudu/wiki/Azure-Web-App-sandbox#file-system-restrictionsconsiderations

You should be able to write the files to the site folder directory (in my case D:\Home\Site\wwwroot) however its not recommended to write files in this directory. I would strongly recommend you to write the files to a storage account either using Storage SDK or functions storage output binding

I hope this helps!

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