Last Monday, on the 14th of November, I got a chance to attend a little workshop on Docker organised by OV Software. It was at the NH Hotel near the facilities of OV Software in The Hague. It is a little far from my place of residence, but I could tag along with a colleague of mine, which helped.
They did a great job of preparing the workshop properly. A VirtualBox image was provided (
https://goo.gl/XUM898). The downloaded file can be "imported" (File -> Import Appliance) into the VirtualBox platform (version minimum is 5.0).
Unfortunately, my labtop is not one of the greatest, and the amount of memory required is too much for it. I had to borrow a labtop from work. If this keeps up, I'll have to buy something better for myself one of these days.
Also, unfortunately, I was unable to attend a previous workshop of which this workshop is a followup, so I did miss some background on Docker, and this was my first foray into this new area. Thankfully, a lot can be found on the internet
1 2, and I already had plenty of experience with Linux, Java, Maven, and just software development in general.
I had small problems getting it to run, for example:
- I had Vx extentions turned off in the BIOS of my labtop. I needed to turn them on.
- PAE - Physical Address Extentions was turned off. It should be on.
- Somehow, when importing the image, I had turned the machine to 32bits. It's a Linux 64bits image.
- It seems it sometimes helps to turn off your USB in the Virtual Machine settings.
The workshop was provided by an employee of OV Software, Jeroen Peeters, who is an excellent and calm speaker.
One of the first things where I went wrong is thinking that Docker is a kind of Virtualisation. It is not. Docker runs within the same Operating System and the containers also all run in the same Operating System. The images, however, can contain everything the container needs to properly run the image. So, they are simply processes running under the same kernel with the same kernel libraries at their disposal, but it is true that these processes are a little better isolated from the rest of the system.
There are plenty of alternatives to Docker, but Docker seems to be the main menu these days:
- LXC
- Rocket, tooling for developers and systemmanagement
- Lmctfy
- OpenVZ
- Canonical LXD, a Ubuntu thing but more isoltation, so more Virtualisation as it also runs system images
To be more specific, the workshop was regarding Continuous Delivery
3 4 with Docker.
During the workshop we set up the following Docker containers inside Docker running on Linux Lite 3.0 LTS (Ubuntu based):
- a container of GitLab that held a git repository of a Java Program
- a container of Jenkins
- a maven container (for inside Jenkins)
- a tomcat container
- a load balancer container (Haproxy)
- a testx container6
So a webhook in the GitLab repo made sure that jenkins was notified if the source code had changed. Jenkins would therefore start a build pipeline, that would build the application and deploy it on Tomcat and would start testing it using TestX
5 (a frontend tester tool sauce over protractor and Selenium).
The github repository containing the Java application can be found at
https://github.com/jeroenpeeters/docker-workshop-java-todolist/. It is a simple TODO list registration tool.
All this is running in one virtual server. For clustering and the like, you could have a look at Kubernetes, the google solution for running Docker on several machines. Complexity is quite high. But there are also other solutions.
It looks very interesting if you are interested in using Continuous Delivery. I do know that System Management (where I work) is very apprehensive about it. I think they fear to lose control on what Developers can do. We are already working with it in some fashion, but it needs to be improved.
References
- [1] Docker
- https://www.docker.com/
- [2] Docker - Installation on Fedora
- https://docs.docker.com/engine/installation/linux/fedora/
- [3] Continuous Delivery: Reliable Software Releases through Build, Test, and Deployment Automation
- https://www.amazon.com/dp/0321601912?tag=contindelive-20
-
- [4] MartinFowler.com - ContinuousDelivery
- http://martinfowler.com/bliki/ContinuousDelivery.html
- [5] TestX
- https://github.com/testxio/testx
- [6] TestX Docker Image
- https://hub.docker.com/r/testx/protractor/
- Nginx - Docker for Java Developers
- https://www.nginx.com/resources/library/docker-for-java-developers/
- The Docker Book - Containerization is the new virtualization
- https://www.dockerbook.com/
- Jenkins
- http://www.jenkins.io
