ASP.NET Core Apps In Docker Swarm Deployed To Azure

Note

Please read the previous post on Docker Swarm before continuing with this one.

Problem

How to deploy a cluster of ASP.NET Core applications using Docker Swam mode in Azure.

Solution

In the previous post, I deployed a Docker Swarm on VMs setup on my local PC, which is fine for testing. In this post, I’ll deploy the same services on a Docker Swarm hosted in Azure, using “Docker EE for Azure”. Let’s start!

Create Public/Private Key

First, we’ll create a public/private key pair, open Git Bash and use the following command (from the directory where you want the key files to be generated). Provide a filename when prompted,

ssh-keygen -t rsa

Note - You may already have Git installed on your PC; if not, you could do it from here.

This will generate two files, file with .pub extension is the public key and we’ll need its content when setting up the Docker for Azure. The Private key will be used when using SSH to connect to Azure,

Create Azure AD Service Principal

In order to setup resources on Azure via scripts Docker provide, we need to set up an application in the AD and use its service principal. Docker provides the required scripts in an image, pull the image and run scripts inside it:

docker pull docker4x/create-sp-azure

docker run -ti docker4x/create-sp-azure fiverswarmapp fiverswarmrg northeurope

Here, fiverswarmapp is the name of application created in Azure AD; fiverswarmrg is the resource group, under which, I want all the resources deployed; northeurope is the region. This will prompt you to authorize access to Azure. Follow the steps and select a subscription:

Once the script finishes executing, you’ll be given your access credentials. Make a note of App ID and App Secret, we’ll need these when setting up Azure for Docker.

Add Docker for Azure (Basic)

Login to Azure Portal and add a new service, search for “docker” and select “Docker EE for Azure (Basic)”.

Configure the basic details using App ID, App Secret and public key created earlier. Select the resource group specified when creating Azure AD Service Principal.

Configure the number of manager and worker nodes.

Review the summary and create the resource. It may take several minutes to set up the resources. Once done, go to your resource group,

Go to “externalSSHLoadBalancer” > Inbound NAT Rules and make a note of Public IP Address and TCP port, we’ll need this to access the master node (to manipulate Docker),

Go to “externalLoadBalancer” and make a note of Public IP Address, we’ll need this to access the deployed application,

Access Master Node via SSH

Open Git Bash and SSH into the master nodes via load balancer,

ssh -i docker-for-azure -p 50000 docker@52.169.94.178

Here, -i specified the file with private key, -p TCP port for load balancer and [email protected] the username/hostname,

Note

The prompt has changed to “swarm-manager”, verifying that we’re now connected to Azure.

Run docker node ls command to list all the nodes,

Tunnel into Master Node via SSH

We want to tunnel into master node so that we can use our local PC as context for Docker commands. Open Git Bash and run,

ssh -i docker-for-azure -p 50000 -fNL 127.0.0.1:2374:/var/run/docker.sock docker@52.169.94.178

Here -fNL specifies location on remote host that listens to the commands

We can now run Docker commands with -H, which will run our commands on the remote host but will use the context of our local PC. For instance run below to list nodes on the remote host, 

docker -H 127.0.0.1:2374 node ls

Note

To stop tunneling, find the process ID via ps command and then kill command to terminate the process.

Deploy Application to Swarm in Azure

Deploying application in Docker Swarm using the stack file is exactly same as discussed in the previous post, with additional -H option to point to the remote swarm in Azure, 

docker -H 127.0.0.1:2374 stack deploy -c docker-compose.yml fiver

Browse to your application using local balancer IP address,

That’s it. This is really cool.

NOTE

Azure Container Service currently doesn’t support Swarm mode, but rather the older standalone Docker Swarm. Hopefully, this will change in the future because the process of setting up Azure Container Service is even simpler, however, a lot of steps are the same e.g. generating keys, accessing via SSH and tunneling etc.