Lecture Notes on Docker and Microservices

Introduction to Docker

• Docker: A tool used to run microservices.
• Microservices: Architectural style where an application is composed of small, independent services.
• Importance of Docker in handling microservices: Docker helps in running, shipping, and managing containers which are essential for microservices.

Understanding Microservices

• Microservices involve different applications that form a larger application.
• Example: Amazon's services like payment, address, cart, etc. each run independently.
• Challenges with monolithic applications: Dependency matrix issues, difficulty in maintenance and updates.
• Microservices break down a monolithic application into independent services, solving these issues.

Monolithic vs. Microservices Architecture

• Monolithic Architecture:

  • Single unit of code handling multiple functions (UI, login, user management, etc.).
  • Challenges in updating and maintaining parts without affecting others.

• Microservices Architecture:

  • Application divided into independent services, each with its own functionality.
  • Benefits: Resolves dependency issues, allows independent development and scaling.
  • Uses REST APIs for communication between services.
  • Docker helps by allowing each service to run in its container, isolated from others.

Docker Overview

• Platform for building, shipping, and running applications in containers.
• Containers are isolated environments containing everything the application needs to run.
• Docker eliminates environment inconsistencies by ensuring a container can run on any system.

Docker Components

• Docker Image: A template with application code and its dependencies.
• Docker Container: A runnable instance of a Docker image.
• Dockerfile: A script containing instructions on how to build a Docker image.
  • Components in Dockerfile: Base image, working directory, copy commands, run commands.
• Docker Network: Allows containers to communicate.
  • Default network: Bridge.

Docker Security and Networking

• Containers are attached to networks for communication.
• Ability to create custom networks for specific applications to enhance security.
• Volumes: Used to persist data generated by containers.
  • Volume Mounts: Persist container-generated data on the host.
  • Bind Mounts: Make data from the host available inside the container.

Docker CLI Commands

• Basic Commands: Docker run, Docker build, Docker push, Docker pull, Docker tag, etc.
• Network and Volume Management Commands.
• Using Docker Hub for storing and sharing images.

Practical Demonstration

• Steps to create a Docker image from a Dockerfile.
• Push Docker images to Docker Hub.
• Pull and run images from Docker Hub.
• Inspect Docker image history and details.

Conclusion

• Docker is essential for handling microservices architecture by providing isolated, controllable environments.
• Docker's flexibility and scalability make it a powerful tool for modern application development and deployment.

Ensure you understand how Docker is used to manage containerized applications and how it fits into the microservices architecture. Review Dockerfile syntax and the basic Docker CLI commands to effectively build and manage Docker images.