Docker – A Valued Tool for DevOps
Docker is one of the most buzzing and trending, talked about topic amongst tech-savvies currently. Usage of Docker containers comfort many woes. The automated process of development, shipping, testing and deployment of the application was a nightmare few years back, but Docker, an open source project, made it possible. It is an automated process inside software containers.
Docker renders an extra layer of abstraction and automation of light weight virtualization on Windows and Linux. Along with the automated process, it is also quick, so it boosts the delivery procedure. It can also be said that Docker notably reduces the delay between writing code and running it on production. Java app development is not only platform for which Docker containers are useful, but in fact it is platform independent.
Analysis of 2016 reveals that 6 million plus crowd adopted the usage of Docker for their application. Gradually, the numbers are escalating to greater extend. Also, many tech giants like Cisco, Google, Huawei, IBM, Microsoft, and Red Hat are the main contributors in the development and enhancement of Docker, along with Docker team.
Docker packages and runs the application in isolated containers. At an instance, many containers can run concurrently on a host. Containers run within host machine’s kernel and don’t require an extra load of hypervisor – so they are loosely isolated and light weight. Basically, Docker containers are virtual machines.
Being a client-server application, Docker possesses of 3 components:
- Server – a Long-running program called a daemon process. It generates ad maintains objects like images, networks, containers, etc.
- REST API – Stipulates interfaces that programs can use to communicate to the daemon and guide it for further steps.
- Command Line Interface (CLI) – Script or code required for talk of REST API and daemon.
The Docker client reports to the Docker daemon, which performs packaging, distributing and executing steps in the Docker containers. As client and daemon can run on the same system, it enhances the convenience. By using REST API, client and daemon setups the communication over UNIX sockets or network interfaces.
With Docker, user can deploy as well as debug the code. If the error is found while automated testing, it is reverted back in form of mail – describing details of the errors. Below are mentioned the main architecture components of Docker:
- Docker Daemon – Listens to API requests and manages Docker objects. It can also talk to other daemons to maintain Docker services. It runs on a host.
- Client – It is a primary medium for users to connect to Docker. The client sends commands to dockerd, and then further steps are performed. A single client can communicate with multiple daemons.
- Images – A read-only template add-on with necessary instructions used to create containers. Compared to other virtual machine technologies, Docker images are small and fast.
- Containers – Described by its associated image as well as configuration options, a container is an executable instance of a Docker image. Using API or CLI, a container can be created, deleted, operated, moved or deleted. With an extensive storage feature of Docker, a container can be connected to more than one network.
- Registry – It mainly stores Docker images. Registry can either be public or private. Docker Hub and Docker Cloud are public registries. Docker store caters an extensive feature where Docker images can be purchased, sold or distributed for free.
- Services – A scheduling service called Swarm enables multi-host, multi-container deployment. Services support the client to compare over multiple Docker daemons that all which combine together to work as a swarm. Swarm was introduced in version 1.12 and introduced.
Benefits of Docker
- Docker is at rage because of CI/CD (Continuous Integration & Continuous Deployment) functionality. CI/CD unites development with testing, which let developers build code simultaneously, push it, and get reverted if any bugs.
- From developer’s perspective, Docker reduces the risk and increases the reliability. Just as the execution environment is alike production environment so the deployment results are also similar. The execution environment possesses requisite infrastructure like the JRE, the application server, VM arguments and other environment variables the application requires to continue.
- Based on operational team view, maintenance of environments for the application has become less struggling with Docker. Easy updating of an existing application and environment.
- Docker does it very simpler to provide safety and/or isolation while troubleshooting new applications
For example, if for any Java App development, to run a Java/Maven-based application without Docker, developers need to install both JDK and Maven on host machine. But with Docker, they get a Maven image from the Docker Hub and can utilize it to develop, test, run and deploy an application.
Package of major benefits like CI, Version Control, Portability, Isolation, and Security, Docker adoption is always a beneficial tool for developer and client. Having extensively favorable characteristics like platform independent cost saving, maintaining appropriate consistency and productivity, compatibility, supporting multi-cloud platforms, enhanced security, and rapid configuration makes Docker a highly adopted tool for deployment and testing.