What is Docker?

The primary goal of this technology is to ensure that applications run the same way in any environment, such as the developer's computer, a test server, or a production environment. To understand what Docker is, one must first understand what a container system is.

What is a Container?

A container is a unit that runs an application along with all its dependencies (libraries, files, environment variables, etc.) in an isolated environment. Each container can have its own file system and network connections, ensuring isolation from other containers and preventing them from affecting each other.

How Does a Container Work?

Technologies like Docker use an image containing all the necessary components to run an application. This image includes a base file system (e.g., Ubuntu Linux) and all other required files. Docker uses this image to create a container and start the application within this container.

Containers are similar to virtual machines but are not the same. Unlike virtual machines, which each contain an entire operating system, containers share the host operating system kernel and provide isolation at the OS level. This makes containers more lightweight and faster to start.

As shown in the image above, without the container system, each component in our web project uses libraries and dependencies on the operating system. This structure brings many problems, such as:

-          Library and dependency conflicts

-          OS version conflicts among components

-          A complicated and costly development environment

•          To solve these problems, the container system is used, providing isolation for more stable operation. Each container contains the libraries and dependencies specific to the project's components, eliminating compatibility issues. Docker facilitates the communication between these libraries and dependencies within the container and the operating system.

• The use of containers is not a process that emerged with Docker. Containers have been in use for about 10 years, but managing container systems is quite difficult and low-level. Docker provides us with many high-level tools to manage these containers.

  There are various types of containers, such as LXC, LXD, and LXCFS. Docker uses the LXC type among these.

   

  Components of Docker?

  ·       Docker Engine: The core runtime of Docker, running on your computer or server, providing all the necessary functions to create, run, and manage Docker containers. It consists of Docker Daemon and Docker Client.

  • Docker Daemon: The background service responsible for creating, running, stopping, and managing containers.
  • Docker Client: The tool that allows users to interact with Docker, enabling them to create, manage, and monitor containers through Docker commands.

  ·       Docker Container: An isolated environment that includes all the dependencies needed to run an application. Each container operates with its own file system, network connections, and processes.

  ·       Dockerfile: A text document used to specify a base image for Docker. It details which image to use, which files to include, and how the application should run with specific parameters. Docker Engine builds a new image by processing the commands in the Dockerfile step-by-step, creating a layered image.

  Docker File Example;

Docker Image: The basis for Docker containers, containing all the files and configurations needed to run an application. Defined in a Dockerfile, the image is processed by Docker Engine and contains the application code, runtime, libraries, and other dependencies.

For example, images are like a cookbook with recipes, while containers are like a person cooking a dish based on those recipes.

·       Docker Registry: A centralized place where Docker images are stored and shared. Docker Hub is a commonly used public registry, but you can also create and use your own private registry. It facilitates the sharing and distribution of Docker images.

Example Scenario;

Let's say a software development team starts developing a web application using Docker:

1. Development Environment Setup: Each developer installs Docker Engine on their computer, creating a common development environment across different operating systems.
2. Packaging the Application with Dockerfile: A Dockerfile is created within the project folder, defining how the application should be packaged and run, including runtime dependencies and configurations.
3. Creating Docker Image: Using the Dockerfile, a Docker image is created, containing all application dependencies and ready to be uploaded to a Docker Registry.
4. Testing the Application: The Docker image is deployed to a test environment, where Docker creates an isolated container to test the application.
5. Deploying to Production: Once testing is successful, the Docker image is deployed to the production environment. Docker containers are quickly started and managed by Docker Engine, making the application ready for use.

This scenario demonstrates how Docker standardizes, isolates, and accelerates the software development process, enabling the team to develop and deploy applications more quickly and reliably.

 

 Advantages of Docker

·       Portability: Docker containers include all necessary components for the application to run, ensuring it works the same on any system. This implements the principle "works on my machine" for any environment.

 

·       Fast and Lightweight: Docker containers start in seconds, as each container is just a process rather than a full virtual machine, freeing you from the sluggishness of virtual machines.

 

 

·       Simplified Deployment: Docker eliminates the need to set up new environments for different servers. Developers just need to download and run Docker images.

 

·       Easy Management and Scaling: Containers are easier to manage and scale compared to virtual machines. Tools like Kubernetes help automate the deployment, scaling, and management of containerized applications.

 

 

·       Efficient Resource Usage: Docker containers use resources more efficiently, allowing more containers to run on a single server compared to virtual machines.

 

·       Support for Multiple OS: Docker supports different operating systems like Windows, Linux, and macOS.

 

 

·       Integration with Cloud Services: Docker can integrate with popular cloud services like AWS, Microsoft Azure, Kubernetes, Istio, and more.

 

 

 

Who Really Has the Potential to Use Containers?

·       Although there is no definitive answer to this challenging question, it is known that in today's technology-driven and dependency-bound business models with "agile" approaches, containers are at least being experimented with by development teams in sectors such as electronic commerce companies, new generation startups providing services over the internet, social platforms, e-government institutions, companies analyzing big data, and similar sectors. Additionally, many global e-commerce companies have been developing their systems on these platforms for some time. In summary,

·       If there is a need for a system that can automatically replicate and multiply service offerings during peak loads,

·       If the service layer needs to be made more modular,

·       If there is a need for load balancing and high availability of services across different geographic locations,

·       If a software company needs to manage the processes used in creating applications in a much more streamlined and automated manner,

·       If the goal is for the developed software to run independently of the platform,

·       Using container architectures will be efficient.

 

Why Do Developers Use Docker?

To utilize the resources of operating systems like Windows, macOS, and Linux, a container structure is needed. Virtualization platforms are preferred to simultaneously use resources such as RAM and CPU on the same system. However, this leads to unnecessary and incorrect usage of operating system resources.

Container configuration, on the other hand, prevents unnecessary resource usage by virtualization platforms. Docker, which uses container technology, helps applications run smoothly by distributing the resources of the operating system. Therefore, the answer to "What is Docker and why is it used?" can be given as the easy setup of web applications and minimizing server costs. Developers who want to provide multiple virtualizations on the same operating system can use the Docker platform, designed with container technology.

 

What is Kubernetes?

Kubernetes is an open-source platform used for the automatic deployment, scaling, and management of containerized applications. Kubernetes makes it easy to manage complex application components, allowing for quick application deployment.

Some reasons and advantages of using Kubernetes are:

• Automation: Kubernetes automates many processes such as application deployment, scaling, load balancing, and automatic repairs. This reduces operational workload and minimizes human errors.

 

• Scalability: Kubernetes allows your applications to automatically scale according to demand, ensuring there are no performance issues even during peak times.

 

• High Availability: Kubernetes offers various configurations to meet high availability requirements. It can automatically create new replicas and route services to ensure uninterrupted operation of applications.

 

• Agility: Kubernetes enables rapid application deployment and easy implementation of changes. This accelerates development processes and provides a competitive advantage.

 

• Portability: Kubernetes can run on any infrastructure and can be used across different cloud providers or in your own data center. This increases the portability of your applications and reduces dependencies.

 

Kubernetes is typically used by large-scale enterprises, software development teams, and cloud providers with complex applications. However, any business or developer community, regardless of scale, can use Kubernetes to manage and deploy their applications more efficiently.

 

Some example scenarios where Kubernetes can be used:

 

Microservices Application: An e-commerce platform may have implemented different functions as microservices, such as customer accounts, product catalog, payment processing, and order management. Kubernetes can run these microservices in separate containers, isolating and managing each one. This allows each service to be scaled, updated, and managed independently.

 

Test Environment Management: A software development team may need different environments to test code changes (e.g., development, integration, QA). Kubernetes can automatically create and manage different test environments. Each environment can be scaled according to requirements and quickly made ready for developers to test their code.

 

High Availability and Backup: A web service provider may have high availability requirements to provide users with an uninterrupted experience. Kubernetes can ensure high availability by automatically distributing and managing backup copies of applications across multiple data centers or cloud regions. Thus, when a data center or region fails, services are automatically redirected to other locations, preventing downtime.

 

Automating Deployment Processes: A software company may want to regularly deliver updates to customers. Kubernetes can automate container-based deployment processes, allowing a new version to be implemented without causing any interruptions. This accelerates the development process and ensures a reliable deployment process.

 

These scenarios illustrate how Kubernetes can be used to manage software development processes and applications more effectively.

 

HATİCE KILIÇ