Docker and Kubernetes workflow together | Explanation in detail

Docker and Kubernetes workflow together

Docker and Kubernetes work together to enable developers to build, deploy, and manage containerized applications efficiently. Here’s an overview of how they interact, including their working flow:

1. Docker:

Purpose: Docker is a platform for developing, shipping, and running applications in containers. Containers package an application and its dependencies together, ensuring consistency across different environments.

Key Components:

• Docker Images: Read-only templates used to create containers. They contain everything needed to run the application, including the code, libraries, and environment variables.
• Docker Containers: Running instances of Docker images. Containers are lightweight and isolated from each other.

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2. Kubernetes:

Purpose: Kubernetes is a container orchestration platform that automates deploying, scaling, and managing containerized applications across clusters of hosts.

Key Components:

• Pods: The smallest deployable units in Kubernetes, which can contain one or more containers. Pods share the same network namespace and can communicate with each other easily.
• Deployments: Define the desired state for pods, including the number of replicas and update strategies.
• Services: Provide stable network endpoints for accessing pods.

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Working Flow of Docker and Kubernetes Together

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1. Building Docker Images:

• Developers create a Dockerfile that defines the application, its dependencies, and how to run it.
• Using the docker build command, developers build a Docker image from the Dockerfile. This image can be stored in a Docker registry (like Docker Hub).

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2. Pushing Images to a Registry:

• After building the image, it is pushed to a container registry. This makes the image accessible to the Kubernetes cluster.

docker push <your-docker-repo>/<image-name>:<tag>

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3. Setting Up Kubernetes:

• A Kubernetes cluster is set up, either locally (using tools like Minikube, Kind, etc.) or in a cloud environment (using services like GKE, EKS, AKS).
• The cluster consists of several nodes, each capable of running pods.

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4. Deploying Applications:

• Developers create Kubernetes manifest files (YAML files) that define the desired state of the application, including:
• Deployments: Specify which Docker image to use and how many replicas (pods) to run.
• Services: Expose the application to external traffic.
• These manifest files are applied to the cluster using kubectl apply -f .yaml.

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5. Kubernetes Creates and Manages Pods:

• Kubernetes reads the deployment manifest and creates the specified number of pods using the Docker image from the registry.
• Each pod runs in its isolated environment, but they share the network namespace, allowing easy communication between containers within the same pod.

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6. Scaling and Updating Applications:

• Kubernetes manages the state of the application:
• If a pod fails, Kubernetes automatically restarts or replaces it.
• Developers can scale applications up or down by changing the number of replicas in the deployment manifest and applying the changes.
• Rolling updates can be performed without downtime by gradually replacing old pods with new ones.

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7. Networking and Service Discovery:

• Kubernetes uses services to expose the application and manage internal and external traffic routing.
• A service provides a stable endpoint (IP and DNS name) to access the pods, abstracting the underlying pod IPs, which can change.

8. Monitoring and Logging:

Kubernetes can be integrated with monitoring and logging tools (like Prometheus and Grafana) to track the health of applications and infrastructure.

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Summary of Workflow

1. Build: Create Docker images.

2. Push: Upload images to a container registry.

3. Deploy: Use Kubernetes manifests to define and deploy applications.

4. Run: Kubernetes creates and manages pods using the specified Docker images.

5. Scale & Update: Kubernetes handles scaling, updates, and ensures high availability.

6. Expose: Use services to expose applications and enable networking.

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Conclusion

In summary, Docker provides the containerization technology to package applications and their dependencies, while Kubernetes offers orchestration to deploy, manage, and scale those containerized applications across clusters. Together, they create a powerful ecosystem for building and managing modern applications in a cloud-native environment.