Unable to run on Azure Function - CamundaCloudTokenProvider makes unauthorised writes to local file system

[matt-ankerson]

The CamundaCloudTokenProvider class maintains a local token cache, using a local file as a means to persist the token. Azure Functions and other Windows hosting environments, don't recommend writes, and may even prohibit writes, to the default file location.

The default location is Environment.SpecialFolder.UserProfile. Below is the description for the UserProfile enumeration:

The user's profile folder. Applications should not create files or folders at this level; they should put their data under the locations referred to by ApplicationData.
Source.

When I run with the default file location on an Azure Function, I observe the following exception.

Status(StatusCode="Unavailable", Detail="Getting metadata from plugin failed with error: Exception occurred in metadata credentials plugin. System.UnauthorizedAccessException: Access to the path 'C:\Program Files (x86)\SiteExtensions\Functions\4.5.1\32bit.zeebe' is denied.
at System.IO.FileSystem.CreateDirectory(String fullPath, Byte[] securityDescriptor)
at System.IO.Directory.CreateDirectory(String path)
at Zeebe.Client.Impl.Builder.CamundaCloudTokenProvider.RequestAccessTokenAsync()
at Grpc.Auth.GoogleAuthInterceptors.<>c__DisplayClass2_0.<b__0>d.MoveNext()

This issue is possibly more of a heads-up, as it may not be an objective of this project to maintain compatibility with Azure Functions, or any specific hosting platform for that matter.

Nevertheless, the CamundaCloudTokenProvider class could have a more agreeable default configuration, to avoid this trap for the uninitiated.

To Reproduce

1. Create a Zeebe client, using the default CamundaCloudTokenProvider class as the token supplier.
2. Supply a LoggingFactory and set the default log level to Trace.
3. Use the client to invoke a process.
4. Deploy process invocation as an HTTP-triggered Azure Function.
5. Trigger the HTTP Function several times over the course of a few hours.

Outcome
The call to invoke the process fails intermittently with an exception, owing to the Function's inability to write to the default file location.

Enviroment

• Azure Function (Windows)
• .NET 6