Adds case study: docker-case-study.md

src/content/docs/containerization/docker-case-study.md

@@ -0,0 +1,309 @@
+# Docker Case Study
+
+**Author:** Borisas Guzitajevas  
+**Date:** January 17, 2025
+
+---
+
+## Table of Contents
+
+1. [Introduction](#1-introduction)  
+2. [History of Docker](#2-history-of-docker)  
+3. [Key Features and Architecture](#3-key-features-and-architecture)  
+   1. [Docker Engine](#31-docker-engine)  
+   2. [Docker Images and Containers](#32-docker-images-and-containers)  
+   3. [Docker Hub (and Other Registries)](#33-docker-hub-and-other-registries)  
+   4. [Container Layering and Union File Systems](#34-container-layering-and-union-file-systems)  
+   5. [Networking and Storage](#35-networking-and-storage)  
+   6. [containerd Under the Hood](#36-containerd-under-the-hood)  
+4. [Use Cases and Applications](#4-use-cases-and-applications)  
+5. [Strengths and Advantages](#5-strengths-and-advantages)  
+6. [Weaknesses and Limitations](#6-weaknesses-and-limitations)  
+7. [Comparison with Similar Technologies](#7-comparison-with-similar-technologies)  
+8. [Demonstration / Basic Usage Example](#8-demonstration--basic-usage-example)  
+   1. [Using Docker Compose](#81-using-docker-compose)  
+   2. [Dockerizing a Minecraft Server](#82-dockerizing-a-minecraft-server)  
+9. [Critical Evaluation and Personal Opinions](#9-critical-evaluation-and-personal-opinions)  
+10. [Conclusion](#10-conclusion)  
+11. [References](#11-references)  
+
+---
+
+## 1. Introduction
+
+Docker is a popular containerization platform that enables developers to package applications and all their dependencies into lightweight, portable containers.  
+These containers can be run consistently on any system equipped with the Docker runtime, whether on a local development machine, a testing environment, or production servers.  
+By isolating applications at the process level, Docker has revolutionized how modern software is developed, deployed, and maintained.
+
+The primary purpose of this case study is to:
+
+- Introduce Docker as a leading containerization technology.  
+- Provide an overview of its history, features, and architectural principles.  
+- Discuss typical use cases and compare Docker to other container solutions.  
+- Critically evaluate Docker’s strengths, weaknesses, and future potential.
+
+> **Note on Docker Licensing:** As of late 2021, Docker Inc. introduced new licensing terms for Docker Desktop, impacting commercial users.  
+> While free for personal, educational, and small-business use, organizations above a certain size or revenue threshold require a paid subscription.  
+> This policy shift underscores Docker’s evolving business model and its focus on commercial sustainability.
+
+---
+
+## 2. History of Docker
+
+Docker was initially released as an open-source project by DotCloud (later renamed Docker, Inc.) in 2013.  
+The idea behind Docker was to simplify the use of Linux containers—a concept that had existed for many years through technologies like LXC (Linux Containers) and `chroot`.  
+However, Linux containers were often challenging to configure and deploy. Docker provided a standardized, developer-friendly interface that made container creation, distribution, and management much more accessible.
+
+Key historical milestones include:
+
+- **2013**: Docker open-sourced, quickly gaining traction in the DevOps community.  
+- **2014**:  
+  - Docker 1.0 released at DockerCon.  
+  - Introduction of Docker Hub, providing a central registry for storing and distributing container images.  
+- **2015**:  
+  - The Open Container Initiative (OCI) was announced to create open, industry-standard container formats and runtimes.  
+- **2016**:  
+  - Docker Swarm mode introduced in Docker 1.12, making container orchestration part of the Docker Engine.  
+- **2017**:  
+  - Docker’s enterprise offerings gained prominence, focusing on large-scale container orchestration and enterprise-grade features.  
+- **2019**:  
+  - Docker Inc. sold its Docker Enterprise business to Mirantis, refocusing Docker on developer workflows and Docker Desktop.  
+- **2020 onwards**:  
+  - Docker continues to evolve, emphasizing Kubernetes integration and developer-centric tools.  
+  - Docker Desktop becomes a standard tool on macOS and Windows, while Docker maintains an open core around container creation.
+
+Over the years, Docker’s impact on the industry has led to widespread adoption of container-based microservices architectures,  
+CI/CD pipelines, and cloud-native development approaches.
+
+---
+
+## 3. Key Features and Architecture
+
+### 3.1 Docker Engine
+
+At the heart of Docker is the **Docker Engine**, a client-server application that includes:
+
+- A **Docker daemon** (the server), which manages images, containers, networks, and volumes.  
+- A **REST API** for interacting with the daemon.  
+- A **CLI client** (the `docker` command), which allows developers to issue commands to the daemon.
+
+### 3.2 Docker Images and Containers
+
+- **Docker Image**: A read-only template containing a set of instructions for creating a container. It typically includes a base operating system layer (e.g., Alpine Linux), plus application files and dependencies.  
+- **Docker Container**: A running (or stopped) instance of an image. Containers include an additional “write” layer on top of the base image, allowing the container to save changes that occur during runtime.
+
+### 3.3 Docker Hub (and Other Registries)
+
+[Docker Hub](https://hub.docker.com/) is a cloud-based registry that allows users to store and distribute Docker images.  
+Public images can be freely pulled, while private images require authentication.  
+Alternatives include Amazon ECR, GitHub Packages, Google Container Registry, and other self-hosted or third-party registries.
+
+### 3.4 Container Layering and Union File Systems
+
+Docker images are built in layers using a **union file system**. Each layer typically corresponds to a step in the Dockerfile (e.g., `FROM`, `RUN`, `COPY`).  
+This approach improves efficiency by reusing layers across multiple images. On modern Linux systems, Docker commonly uses the **overlay2** storage driver for this layered filesystem approach.
+
+### 3.5 Networking and Storage
+
+- **Networking**: Containers can communicate via virtual networks, bridging, host networking, or overlay networks. Complex topologies can be set up to isolate or expose services as needed.  
+- **Storage**: Data persistence is possible through **named volumes** or **bind mounts**, ensuring container data is not lost after container termination.
+
+### 3.6 containerd Under the Hood
+
+Although Docker is widely recognized as a complete container platform, it is built on top of **containerd**—an industry-standard container runtime.  
+In turn, containerd uses **runc**, the default container runtime implementation that meets the Open Container Initiative (OCI) specification.  
+By layering these components, Docker exposes a user-friendly CLI and workflow while delegating low-level container management to containerd and runc.
+
+---
+
+## 4. Use Cases and Applications
+
+Docker is widely adopted across various industries and project sizes. Common use cases include:
+
+1. **Microservices Architecture**  
+   Breaking down monolithic applications into smaller, independently deployable services. Each service runs in its own container, making it easier to scale, update, and maintain.
+
+2. **Continuous Integration / Continuous Deployment (CI/CD)**  
+   By packaging applications into containers, developers can ensure that software builds and tests run consistently in development,  
+   staging, and production environments. Tools like Jenkins, GitHub Actions, and GitLab CI integrate seamlessly with Docker.
+
+3. **Testing and Isolation**  
+   Containers allow QA teams to spin up fresh environments quickly, test software, and tear them down without affecting other systems.
+
+4. **Cloud-Native Development**  
+   Docker containers run efficiently on major cloud platforms (AWS, Azure, Google Cloud).  
+   Container orchestration tools like Kubernetes further streamline the deployment and management of containerized applications at scale.
+
+5. **Local Development Environments**  
+   Docker Desktop for macOS and Windows helps create consistent local development environments.  
+   Developers can avoid “works on my machine” syndrome by using standardized container images.
+
+---
+
+## 5. Strengths and Advantages
+
+- **Consistency Across Environments**  
+  Applications packaged as Docker containers run the same way in development, testing, and production environments, reducing deployment issues.
+
+- **Lightweight and Efficient**  
+  Containers share the host OS kernel, making them more resource-efficient than traditional virtual machines.
+
+- **Simplified Deployment**  
+  Docker’s CLI, Dockerfiles, and official images on Docker Hub make it straightforward to build, ship, and run containers.
+
+- **Large Ecosystem and Community**  
+  A robust ecosystem of Docker images, plugins, and third-party tools exists, with strong community support and documentation.
+
+- **Scalability**  
+  Containers can be started or stopped quickly, making horizontal scaling easier. With orchestration (Docker Swarm or Kubernetes), Docker excels in dynamic scaling scenarios.
+
+---
+
+## 6. Weaknesses and Limitations
+
+- **Security Concerns**  
+  Although containers provide process isolation, they share the host kernel. A kernel vulnerability could compromise all containers.  
+  Proper configuration, rootless containers, and frequent patching are essential.
+
+- **Persistent Storage Challenges**  
+  Docker containers are ephemeral by design. Storing data persistently or sharing it among containers can be more complex than in stateless workloads.
+
+- **Networking Complexity**  
+  Docker’s virtual network layer is flexible, but complex network topologies or strict security requirements can complicate container networking.
+
+- **Overhead for Small Projects**  
+  For very simple applications, using containers can add unnecessary complexity compared to a direct deployment on a single server.
+
+- **Rapid Changes in the Ecosystem**  
+  Docker and its ecosystem evolve quickly. Keeping up with best practices, new releases, and potential deprecations requires continuous learning.
+
+---
+
+## 7. Comparison with Similar Technologies
+
+While Docker pioneered modern containerization, there are several alternatives or complementary tools in the container ecosystem:
+
+- **Podman**  
+  - Developed by Red Hat. Daemonless container engine.  
+  - Can run containers in a rootless mode, improving security.
+
+- **LXD**  
+  - Canonical’s container hypervisor for system containers (full OS containers).  
+  - Focuses on OS-level virtualization with more extensive system-level isolation.
+
+- **containerd**  
+  - An industry-standard container runtime underpinning Docker.  
+  - Often used directly in Kubernetes as a CRI (Container Runtime Interface)-compliant runtime.
+
+- **Kubernetes**  
+  - Not a direct alternative for building containers, but a container orchestration platform.  
+  - Works with Docker, containerd, or other runtimes to manage containerized workloads at scale.
+
+Despite these alternatives, Docker remains a standard tool for containerizing applications and is widely supported by third-party services and CI/CD pipelines.
+
+---
+
+## 8. Demonstration / Basic Usage Example
+
+### 8.1 Using Docker Compose
+
+For multi-container applications (e.g., a Python app plus a separate database), **Docker Compose** helps define and run containers together.  
+Here’s a minimal `docker-compose.yml` example:
+
+```yaml
+version: "3.9"
+services:
+  web:
+    build: .
+    ports:
+      - "5000:5000"
+  db:
+    image: postgres:alpine
+    environment:
+      POSTGRES_USER: myuser
+      POSTGRES_PASSWORD: mypassword
+```
+Bring up both containers (web and db) with:
+
+bash
+Copy
+Edit
+docker compose up -d
+This makes local development of complex, multi-service applications far simpler.
+
+### 8.2 Dockerizing a Minecraft Server
+
+While the previous examples focused on web or database apps, Docker can also host a game server, demonstrating its flexibility and ease of use.  
+For instance, **Minecraft** can be run in a container without installing Java or the server files directly on the host machine.  
+This underscores how Docker abstracts away environment setup and simplifies deployment—even for non-traditional workloads.
+
+Below is a minimal example using the popular `itzg/minecraft-server` image:
+
+```bash
+docker run -d \
+  --name minecraft \
+  -p 25565:25565 \
+  -e EULA=TRUE \
+  -e MEMORY=2G \
+  -v /path/on/host/minecraft-data:/data \
+  itzg/minecraft-server
+```
+## Key Points
+
+- **Port Mapping**:  
+  `-p 25565:25565` maps the container’s Minecraft port to the host so external players can connect (e.g., `your.public.ip:25565`).
+
+- **Environment Variables**:  
+  - `-e EULA=TRUE` automatically accepts Minecraft’s EULA.  
+  - `-e MEMORY=2G` sets the Java heap size to 2 GB.
+
+- **Persistent Storage**:  
+  `-v /path/on/host/minecraft-data:/data` ensures world data, server configs, and logs remain on the host. You can remove or update the container without losing your world.
+
+- **Isolation and Repeatability**:  
+  The container has its own dependencies (e.g., the correct Java version) isolated from your host environment.  
+  Easy to spin up or tear down the server on multiple machines.
+
+> Although Minecraft may seem “non-enterprise,” the underlying Docker concepts—port mapping, environment variables, persistent volumes—are the same as any containerized service.
+
+---
+
+## 9. Critical Evaluation and Personal Opinions
+
+In practice, Docker has transformed the way software teams develop and deploy applications by abstracting away environment configuration and dependencies.  
+It accelerates development cycles and reduces “it works on my machine” issues. However, it is not a silver bullet. For teams with modest requirements or very simple projects,  
+Docker might introduce unnecessary complexity—maintaining Dockerfiles, registries, and orchestrators can be overkill for a simple web app.
+
+For microservices or larger-scale applications, Docker is nearly indispensable, especially when combined with orchestration tools.  
+Its powerful ecosystem (including Docker Compose and Docker Desktop) makes local development of distributed services more straightforward.  
+Organizations with global footprints or rigorous CI/CD pipelines benefit immensely from containerization.
+
+Regarding security, teams should consider rootless containers or alternatives like Podman if they need enhanced isolation.  
+Docker’s decision to sell its Enterprise product line in 2019 and adjust licensing for Docker Desktop in 2021 reflect the company’s shift in focus.  
+While Docker remains the “de facto” tool for building images, many production environments now rely on Kubernetes or containerd for container orchestration at scale.
+
+---
+
+## 10. Conclusion
+
+Docker’s emergence as a containerization solution has led to a fundamental shift in how software is packaged, distributed, and deployed.  
+By providing a consistent environment across development and production, Docker reduces friction between teams and simplifies many aspects of DevOps workflows.  
+While it introduces new complexities in networking, security, and persistent storage, its benefits often outweigh the downsides for projects of moderate to large scope.
+
+As the container ecosystem evolves, Docker’s role continues to adapt. It remains the standard for building container images, even as orchestration tools (like Kubernetes)  
+and alternative runtimes (like containerd, CRI-O, and Podman) gain traction. Teams considering Docker should evaluate their project requirements and invest time in learning  
+best practices, security hardening, and orchestration strategies to fully leverage Docker’s potential. Keeping an eye on licensing changes and enterprise product shifts  
+will also be important for organizations heavily reliant on Docker Desktop or commercial Docker offerings.
+
+---
+
+## 11. References
+
+- [Docker Official Documentation](https://docs.docker.com/)
+- [Docker GitHub Repository](https://github.com/docker)
+- [Open Container Initiative (OCI)](https://opencontainers.org/)
+- [Podman Official Documentation](https://podman.io/)
+- [Kubernetes Documentation](https://kubernetes.io/docs/home/)
+- [Docker Minecraft Server](https://github.com/itzg/docker-minecraft-server)
+- [containerd GitHub Repository](https://github.com/containerd/containerd)
+