Docker Orchestration 27 November, 2020   

This article is written for individual review of PPL CS UI 2020

In this instance I will talk about Docker.

What is Docker?

Docker is a tool designed to create, deploy and run applications easier by using containers.

What is Container?

Containers is a tool to allow developer(s) to package up a program with all of the parts it needs, such as libraries and other dependencies.

Why the needs for this tool?

By packaging it in one container, developer can easily run the application on any other machine regardless of any customized settings differed from the machine used for writing the code. No more searching what missing dependencies needed for the application.

Docker sounds similar to virtual machine, but it differs where the host kernel is used instead of hypervisor used by VM. Dockers abstracting the OS, unlike VM where instead it abstracts the hardware. Consequently, Dockers need much less space size than Virtual Machines. It also differents from Virtual Environments where developers are still in host OS, with Docker, developers can run it on Ubuntu, Debian, Mint etc.

Advantage

There is certains benefits developers get when using docker :

1. Consistency, the program always runs using same environment no matter which server or laptop they are running on. This means less time spent setting up environments and eliminate "it works on my machine" problem
2. Simplicity, Developers can put docker, code and deploy it without any problems. The requirements of host's infrastructure are no longer needed. The application can be run without disturbance from the host's infrastructure
3. Faster Deployment, Because it is much smaller than VM and does not boot an OS, Deployment of application can be reduced into seconds.

Docker as a service is consisted of three components :

• Software: The Docker daemon, called dockerd, is a process which manages Docker containers and handles container objects.
  
• Objects: Various entities used to assemble an application in Docker such as Docker container, which is a standardized & encapsulated environment where applications runs, Docker image, read-only template used to build containers, and Docker service which allows containers to be scaled across multiple docker daemons.
  
• Registries: a repository for Docker images. Docker software connect to registries to pull images for use or push images that which have been built.

How to build it?

To setup Docker, many tutorial is provided online, including from it's developer. You can also search other tutorial, for example this one

For this PPL project, unfortunately I don't use Docker. There are many reasons, such as I don't make this project from scratch, I'm inheriting it to develop additional features and my predecessors didn't seem to use Docker. I'm not confident in building Docker image for projects builded by others.

Also, I'm working alone in developing this projects and considering my mobility halted by Covid, Developing Dockers for use in other laptops is not my current priority. Maybe when I have time in the future I would build it. For now I'm still satisfied using Virtual Enviroments.