App Service, App Settings, and Container Registry with Managed Identity
Managed Identities in Azure are a wonderful thing. No passwords to change, no keys to rotate. The biggest shame is that frequently they seem to be implemented as an afterthought. One example I recently ran into was the use of an App Service Managed Identity to pull a container from Azure Container Registry. While you can configure an App Service to pull from ACR with a Managed Identity, what the documentation doesn’t tell you is that you still need the DOCKER_REGISTRY_SERVER_USERNAME and DOCKER_REGISTRY_SERVER_PASSWORD App Settings to be configured on the App Service.