Continuous Delivery with Containers – Amending a VSTS / Docker Hub Deployment Pipeline with Azure Container Registry

In this blog series on Continuous Delivery with Containers I'm documenting what I've learned about Docker and containers (both the Linux and Windows variety) in the context of continuous delivery with Visual Studio Team Services. It's a new journey for me so do let me know in the comments if there is a better way of doing things!

In the previous post in this series I explained how to use VSTS and Docker to build and deploy an ASP.NET Core application to a Linux VM running in Azure. It's a good enough starting point but one of the first objections anyone working in a private organisation is likely to have is publishing Docker images to the public Docker Hub. One answer is to pay for a private repository in the Docker Hub but for anyone using Azure a more appealing option might be the Azure Container Registry. This is a new offering from Microsoft -- it's still in preview and some of the supporting tooling is only partially baked. The core product is perfectly functional though so in this post I'm going to be amending the pipeline I built in the previous post with Azure Container Registry to find out how it differs from Docker Hub. If you want to follow along with this post you'll need to make sure  you have a working pipeline as I describe in my previous post.

Create an Azure Container Registry

At the time of writing there is no PowerShell experience for ACR so unless you want to use the CLI 2.0 it's a case of using the portal. I quite like the CLI but to keep things simple I'm using the portal. For some reason ACR is a marketplace offering so you'll need to add it from New > Marketplace > Containers > Container Registry (preview). Then follow these steps:

1. Create a new resource group that will contain all the ACR resources -- I called mine PrmAcrResourceGroup.
2. Create a new standard storage account for the ACR -- I called mine prmacrstorageaccount. Note that at the time of writing ACR is only available in a few regions in the US and the storage account needs to be in the same region. I chose West US.
3. Create a new container registry using the resource group and storage account just created -- I called mine PrmContainerRegistry. As above, the registry and storage account need to be in the same location. You will also need to enable the Admin user:
   

Add a New Docker Registry Connection

This registry connection will be used to replace the connection made in the previous post to Docker Hub. The configuration details you need can be found in the Access key blade of the newly created container registry:

Use these settings to create a new Docker Registry connection in the VSTS team project:

Amend the Build

Each of the three Docker tasks that form part of the build need amending as follows:

• Docker Registry Connection = <name of the Azure Container Registry connection>
• Image Name = aspnetcorelinux:$(Build.BuildNumber)
• Qualify Image Name = checked

One of the most crucial amendments turned out to be the Qualify Image Name setting. The purpose of this setting is to prefix the image name with the registry hostname, but if left unchecked it seems to default to Docker Hub. This causes an error during the push as the task tries to push to Docker Hub which of course fails because the registry connection has authenticated to ACR rather than Docker Hub:

It was obvious once I'd twigged what was going on but it had me scratching my head for a little while!

Final Push

With the amendments made you can now trigger a new build, which should work exactly as before except now the docker image is pushed to -- and run from -- your ACR instance rather than Docker Hub.

Your next question is probably going to be how can I get a list of the repositories I've created in ACR? Don't bother looking in the portal since -- at the time of writing at least -- there is no functionality there to list repositories. Instead one of the guys at Microsoft has created a separate website which, once authenticated, shows you this information:

If you want to do a bit more you can use the CLI 2.0. The syntax to list repositories for example is az acr repository list -n <Azure Container Registry name>.

It's early days yet however the ACR is looking like a great option for anyone needing a private container registry and for whom an Azure option makes sense. Do have a look at the documentation and also at Steve Lasker's Connect(); video here.

Cheers -- Graham