Docker Misconceptions

July 21, 2015 § 2 Comments

I read a great blog post on Docker over at Valdhaus. You can find it here. All credit goes to them. I thought there were some really great misconceptions that I want to highlight.

1. If I learn Docker I don’t have to learn the other systems stuff – Boy is this not true. Docker makes things very simple for the developer but not for the operations team. Managing large servers to run the Docker run-time and be able to tune the server to best be able to be a Docker host is still a job for the professional mechanic, not Tim the Toolman Taylor. Just like any other technology the “hello world” example is simple and easy but getting to running production workloads is a big leap. Insure you have good operational understanding of Docker before you get there.

2. You should only have one process per Docker container – This is another problem with the “Hello World” example. Proper crafting of Docker container content is a big key to success, not only at the runtime perspective but also at the Docker file level. Create proper layers in the Docker file is important. Levels of abstraction are usually game changers for any type of architecture and Docker is no exception. I like the mindset of creating Docker containers as a “role based virtual machine” used in the blog. Having the single process mindset caused the wrong level of abstraction in many cases. I also highly recommend reading the referenced blog “Microservices – Not a free lunch.”

3. If I use Docker I don’t need an orchestration tool (my edit) – the Valdhaus blog really talks about the need for orchestration and promotes the use of Ansible. Of course being from IBM I would encourage UrbanCode Deploy, but the point is well taken. Coordinating the deployment of containers and the associated networking is challenging enough, but you can do some really cool blue/green deployment strategies to achieve seamless zero downtime production deployments using an orchestration tool.

The rest of the Valdhaus blog is great but these 3 points were targeted at where I spend my time. The big benefits of Docker are achievable as long as you spend time insuring the systems underneath your Docker environment are well maintained. Developers love Docker. Operations teams can also love Docker as long as they understand how to manage it.

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