Tuesday, May 12, 2015

Software Containerization via Docker - First look and some thoughts

I was hunting behind the architecture of micro services and its advantages in distributed systems development and maintenance. The word 'Docker' stuck me when I heard that word multiple times in  one of the talk regarding micro services in Netflix. In that talk Adrian repeatedly telling that the Docker helped them a lot to deliver fast.They are not at all bothered by "works in my machine" scenarios. Then I started investigating what is Docker?

What is Docker

Docker is a software containerization technique where software with its dependencies can be run independently in an isolated environment. The container is run by container engine which is running inside Linux OS. If we are hosting an web application inside web server hosted in the container, we need to explicitly open ports for that container to establish communication. There are APIs to do container operations. The main advantage is friction less movement of executable software from one environment to another environment. If we make sure once our software is running inside the docker container, that container can run in any place where the docker engine is available

This easily leads to a question of

What is the difference between a virtual machine and docker container?

What I have understood from my analysis is virtual machine is an OS running inside another OS. It is heavy as the host operating system. If we want to utilize same hardware for multiple operating systems, we can go for that. But if we need mobility of software only better way is container concept.

Solomon, Founder and CEO of Docker Inc simply comparing docker ecosystem with logistics industry in his talk posted in www.docker.com

To me, the virtual machines looks like below.
But is this what we need when we need to transport software in its running condition? Absolutely no. That is where container comes into play as follows.

The vehicle which is carrying the package doesn't need to bother about what is inside container as long as it adhere to standard container specifications. In software, we really don't need to carry the operating system when we want to move our software. But we need to carry the dependencies of course.

Is there any standard for containers in software industry as in logistics

I don't think there is one right now. Docker can have it's own container file format and APIs to manage the containers where competitors can have their own. But a standardization is really required and soon that would evolve as everybody needs to move their software such as on premise to cloud and vice versa.

Some Docker facts

  • It uses new API in Linux kernel
  • Right now the Docker engine can only work on top of Linux
    • If we want to host Docker engine in Windows or Mac, we need to use Linux VMs
  • The containers are Linux specific. Though we can host .Net via Mono.
  • It is used for easing the deployment and maintenance of distributed application. No meaning in running UI app inside docker container.
  • There is docker app store where we can uploaded our containers or get containers from others. Same like other app store. The major difference is we don't need to install the app, instead just use the already installed and configured software by running docker container on docker engine.

Is Docker ready for production?

I think yes, if we are dealing with services hosted inside Linux server boxes. For Microsoft .Net community its not. Again it's my opinion after some research may vary from person to person and scenario to scenario.

Docker from .Net developer's view

As Docker is not yet ready to directly run on Windows platform, I don't think, its the time for .Net developers to enter into the Docker world. Of course they can try out docker commands and host .Net services using Mono etc... Another thing we need to notice is that there is no windows containers which can be run by the docker engine.

There is a tool called Boot2Docker available for Windows users to host a minimal Linux OS and run the Docker engine inside it. Once the engine ie runtime is available any docker container can be run inside it.

Again, the main bottleneck why we can't run Docker engine in Windows is the usage of Linux specific APIs to build the Docker engine.

The good news is Microsoft announced partnership with Docker to bring the technology into Windows ecosystem. As usual it seems the strategy is cloud first. But in near future we can get Windows Servers supporting docker containers out of the box. More than that, if a standard for containerization comes as part of partnership, that would be a mile stone in software industry.

Other software container technologies

Docker is way ahead in the container business. But there are competitors as well in the software container business. Rock-It from CoreOS, ElasticBox , DrawBridge from Microsoft to name few.


For those who are not able to follow what is Docker and containerization, try google or just wait for couple of months, you will certainly start hearing the word.


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