Why isn't Azure App Service Deploy copying files to my Web App's wwwroot?

February 20, 2019
[ azure  azure-devops  pipelines  ]


I was recently working with a collegue to deploy a Sitecore app to Azure via Pipelines. The release was running successfully, but the deployed files didn’t seem to be overlaying the required, pre-loaded Sitecore files. When we viewed /site/wwwroot from Kudu, we were seeing only the files from the build artifacts; when we viewed the same directory from FTP, we were seeing only the Sitecore files. What gives?

The cause: Azure App Service Deploy task version

Sometime over the past few months, the Azure App Service Deploy release task versioned to 4.*. In that release, the Microsoft team created an auto-detect feature that tries to guess the best method for code deployment to your Web App. In our case, it chose the new preferred method called Run From Package, which has a few quirks.

What’s new in version 4.*

These are the new features in 4.* per the Azure DevOps UI at the time of writing:

  • Supports Zip Deploy, Run From Package, War Deploy
  • Supports App Service Environments
  • Improved UI for discovering different App service types supported by the task
  • Run From Package is the preferred deployment method, which makes files in wwwroot folder read-only
  • Click here for more information.

Most relevant for us is the Run From Package feature.

How does that work?

When the release task deploys using Run From Package, it does a few things:

  • Zips build artifacts and uploads to /data/SitePackages/.
  • Creates a /data/SitePackages/packagename.txt file whose contents point to the deployed zip filename.
  • Sets a new Application Setting to the app of WEBSITE_RUN_FROM_PACKAGE=1.

The effect of the WEBSITE_RUN_FROM_PACKAGE setting is that the /site/wwwroot/ directory now vitually points to the deployed zip file, not to the actual underlying file system. Try it: download the package zip from /data/SitePackages/ and compare contents with /site/wwwroot/ in Kudu. If you extract FTP credentials from the publish profile and access /site/wwwroot/, there is a completely different site of files. Here’s what I’m seeing from a fresh .NET Core MVC deployment:





The solution

When Microsoft updated the release task, they made a major change to the default behavior of the task and hid the option under the Additional Deployment Options section.


When the Select deployment method option is not checked, the task appears to prefer the Run From Package option. Since I want to overlay my deployment files over existing files, the solution for us was to select the option and choose Web Deploy as our deployment method.


Web Deploy matches the previous behavior of the release task in that it overlays my build artifacts without removing any of the destination files:


I also noted that when I switched the deployment method to Web Deploy, the release task automatically set the WEBSITE_RUN_FROM_PACKAGE setting to 0, which disabled the /site/wwwroot/ mismatch we observed.

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