Containerization

What is Containerization

• Containerization is a lightweight alternative to a virtual machine that involves encapsulating an application in a container with its own operating system.
• A container takes its meaning from the logistics term, packaging container. When we refer to an application container, we mean packaging software.

Why Cotainers

• Reduced Delivery Time
• Increase Productivity
• Cloud Compatibility
• Environment-agnostic deliverables

Containers

• flexible
• Lightweight（GB vs MB）
• Interchangeable
• Portable
• Scalable
• Stackable

VM and Containers Difference

Virtual Machine	Containers
Each VM includes the application, the necessary binaries and libraries and an entire guest operating system, all of which may be tens of GBs in size	Containers include the application and all of its dependencies, but share the kernel with other containers. They run as an isolated process in userspace on the host operating. They are also not tied to any specific infrastructure—Docker Containers run on any computer , on any infrastrusture and in any cloud

Docker

What is Docker

• The leading containerization technology
• Written in Go
• Avaliable in both community and enterprise editions
• runs natively on Linux, MacOs and Windows
• Consiss of multiple Parts

Docker Engine

• Consists of three parts
  • Server which runs the Docker daemon
  • REST API for communication between client and daemon
  • CLI client(docker)

Terminology for Docker

Term	Explanation
Image	Executable package containing the code, runtime, libraries, environment and configuration Read Only Can be Stored and transferred
Container	A runtime instance of an image An isolated workspace on the host machine
DockerFile	A file containting instructions how to create an image

Docker Compose

• Multi- container application made easy
• Good for development environments and single host deployment
• configured with a YAML file

Containerization for web application

The advantage

• Image as deliverable
• Good cloud support
  • AWS, Azure, Digital Ocean, OpenStack, Google Compute Engine
• On container for each process

The disadvantage

• Yet antoher layer
• A new tool to grasp
• Monitoring can be hard
• Managing Clustered Systems require additonal tools