Error "Web Deploy cannot modify the file on the destination because it is locked by an external process" in Octopus deploy

Question

We are deploying into azure using Octopus deploy. We are using it since more than a year, and suddenly we started (about 3 weeks ago) to get errors on few deployments.

Microsoft.Web.Deployment.DeploymentDetailedClientServerException: Web Deploy cannot modify the file 'msvcr120.dll' on the destination because it is locked by an external process. In order to allow the publish operation to succeed, you may need to either restart your application to release the lock, or use the AppOffline rule handler for .Net applications on your next publish attempt. Learn more at: http://go.microsoft.com/fwlink/?LinkId=221672#ERROR_FILE_IN_USE

We have the webapp running and always on and we have the app setting 'MSDEPLOY_RENAME_LOCKED_FILES' to 1 that in theory prevents this.

Does anyone knows if something was changed in azure or octopus?

Answer 1

There are a number of reasons files may be locked during deployment. You should be able to get an idea of what may be locking files by using the kudu process explorer, which you can access using the url {yoursite}.scm.azurewebsites.net.

In order to avoid the locking issue altogether, you could make use of slots to achieve a zero downtime deployment if that's an option for you. In this case you could stop the site or enable App Offline which should unlock any files and allow the deployment to succeed after which a slot swap will make the deployment live. App Offline is preferred over using MSDEPLOY_RENAME_LOCKED_FILES, but will take the application offline during the deployment. Octopus also has support for this as an option on the Deploy an Azure Web App step itself, so may be worth a try even without slots.

You can use custom pre/post deployment scripts as part of your Deploy an Azure Web App to make use of the Stop-AzureRmWebAppSlot, Start-AzureRmWebAppSlot and Switch-AzureRmWebAppSlot Powershell commands Azure commandlets to achieve the above.

An alternative may be to use zip deployments, however, the Deploy an Azure Web App Octopus step doesn't have first class support for this quite yet. It can still be achieved using a Run an Azure PowerShell Script along with a package references if this is what you are wanting to do.