What is a swarm?
The cluster management and orchestration features embedded in the Docker Engine are built using SwarmKit. Docker engines participating in a cluster are running in swarm mode. You enable swarm mode for an engine by either initializing a swarm or joining an existing swarm. A swarm is a cluster of Docker engines, or nodes, where you deploy services. The Docker Engine CLI and API include commands to manage swarm nodes (e.g., add or remove nodes), and deploy and orchestrate services across the swarm.
I was recently trying to come up with a script that generates the docker swarm cluster – ready to take container work loads on Microsoft Azure. I thought, Azure Container Service (ACS) should already have supported that. However, I figured, that’s not the case. Azure doesn’t support docker swarm mode in ACS yet – at least as of today (25th July 2017). Which forced me to come up with my own RM template that does the help.
What’s in it?
The RM template will provision the following resources:
- A virtual network
- An availability set for manager nodes
- 3 virtual machines with the AV set created above. (the numbers, names can be parameterized as per your needs)
- A load balancer (with public port that round-robins to the 3 VMs on port 80. And allows inbound NAT to the 3 machine via port 5000, 5001 and 5002 to ssh port 22).
- Configures 3 VMs as docker swarm mode manager.
- A Virtual machine scale set (VMSS) in the same VNET.
- 3 Nodes that are joined as worker into the above swarm.
- Load balancer for VMSS (that allows inbound NATs starts from range 50000 to ssh port 22 on VMSS)
The design can be visualized with the following diagram:
There’s a handly powershell that can help automate provisioing this resources. But you can also just click the “Deploy to Azure” button below.
The entire scripts can be found into this GitHub repo. Feel free to use – as needed!
Docker makes application deployment easier than ever before. However, most of the Docker articles are often written how to containerized application that runs on Linux boxes. But since Microsoft now released windows containers, the legacy (yes, we can consider .net 4.5 as legacy apps) .net web apps are not left out anymore. I was playing with an ASP.net 4.5 web application recently, trying to make a container out of it. I have found the possibility exciting, not to mentioned that I have enjoyed the process entirely. There are few blogs that I have found very useful, especially this article on FluentBytes. I have however, developed my own scripts for my own application, which is indifferent than the one in FluentBytes (thanks to the author), but I have combined few steps into the dockerfile – that helped me get going with my own containers.
If you are reading this and trying to build container for your asp.net 4.5 applications, here are the steps: In order to explain the process, we’ll assume our application is called LegacyApp. A typical asp.net 4.5 application.
- We will install Docker host on windows.
- Create a directory (i.e. C:\package) that will contain all the files needed to build the container.
- Create the web deploy package of the project from Visual studio. The following images hints the steps we need to follow.
Image: Create a new publish profile
Image: Use ‘Web Deploy Package’ option
Important note: We should name the site in the following format Default Web Site\LegacyApp to avoid more configuration works.
- Download the WebDeploy_2_10_amd64_en-US.msi from Microsoft web site
- I have ran into an ACL issue while deploying the application. Thanks to the author of FluentBytesarticle, that provides one way to solve the issue by using a powershell file during the installation. We will create that file into the same directory, let’s name it as fixAcls.ps1. The content of the file can be found here
- We will create the dockerfile into the same directory, with the content of this sample dockerfile
At this moment our package directory will look somewhat following:
Now that the container is running, we can start browsing your application. we can’t use the localhost or 127.0.0.0 on our host machine to browse the application (unlike Linux containers), we need to use the machine name or the IP address in our URL. Here’s what we can do:
- We will run the inspect command to see the container IP.
C:\> docker -inspect
- Now we will take the IP from the JSON and use the IP on our URL to navigate to the application.
The complete dockerfile can be found into the Github Repo.