`CloudPlatform` determination does not work correctly in Azure App Service (Windows)

[shibayan]

CloudPlatform for Azure App Service was added in Pull Request #25829, but the environment is not correctly identified on App Service (Windows) because the WEBSITES_ENABLE_APP_SERVICE_STORAGE environment variable, which exists only on App Service (Linux), was used to identify the environment.

#25829 (comment)

Therefore, if you are running a Spring boot application on Windows, you may need to configure additional settings for handling Forwarded headers.

There are a number of environment variables that exist on both Windows and Linux, but the following three are probably unique to Azure App Service.

• WEBSITE_INSTANCE_ID
• WEBSITE_RESOURCE_GROUP
• WEBSITE_SKU

Hello @jdubois, I would like to know if you have any opinions on this.

[wilkinsona]

Thanks for raising this, @shibayan. When the original support was added, I shared @cuspymd's concern that WEBSITE_SITE_NAME was too generic to use on its own. I have similar concerns about WEBSITE_INSTANCE_ID, WEBSITE_RESOURCE_GROUP, and WEBSITE_SKU. Ideally we'd find another environment variable that's more Azure-specific while also being present on Windows.

Let's wait for the opinion of @jdubois before we change anything here.

[jdubois]

Thank you! I’ll have a look next week, when I’m back from holidays.

[jdubois]

I just had a talk with @ccompy who knows this far better than I do, and those three environment variables look good.
I'm going to do a PR to fix this in the next couple of days, if that's fine with everyone.

[wilkinsona]

Thanks, @jdubois. I'm still a bit concerned about false positives as those three are all rather generic. If there's no single alternative that's more Azure-specific, I guess my concerns could be alleviated somewhat by looking for all three in combination.

[jdubois]

Unfortunately there isn't one... And yes I believe the combination of all 3 variables makes it pretty unique.