The Modern Application Journey
From a developer's idea to a global service, this is the story of an application's journey in the world of DevOps and Kubernetes.
Step 1: Write Code
Everything starts here. The developer turns an idea into code using their preferred language. This is the heart of the application.
- Writing application logic.
- Version control using Git.
- Initial testing on the local machine.
Step 2: Dockerize
To solve the "but it works on my machine!" problem, we package the application inside a Container using Docker. A `Dockerfile` describes the required environment to create an isolated, portable box.
- Write a
Dockerfileto describe the application environment. - Build a Docker image using
docker build. - The image now contains everything: code, libraries, and settings.
Step 3: Continuous Integration (CI)
When a developer pushes a new change, the CI Pipeline starts automatically. It builds the code and runs tests to detect errors early and ensure quality.
- Pull the latest changes from Git.
- Run tests (Unit & Integration Tests).
- On success, a new Docker image is built.
Step 4: Push to Registry
After building the image and passing tests, it is pushed to a central image repository (Container Registry) like Docker Hub or GCR. This registry is the source of truth for application images.
- Give a unique
tagto the image (e.g.,v1.2.0). - Use
docker pushto upload the image. - The image is now ready for deployment in any environment.
Step 5: Declarative Manifest (YAML)
Now, we tell Kubernetes what we want. We don't give commands; we describe the "Desired State" in YAML files. You choose the right tool for your task and then describe it.
- Write a YAML file to describe your chosen Workload Resource (e.g., deployment.yaml or job.yaml).
- Create a
service.yamlfile to enable networking if needed. - Apply the settings using
kubectl apply -f ..
Choose the right tool for your job:
| Application Type (Task) | Workload Resource |
|---|---|
| Web App or API (Stateless) | Deployment |
| Database or stateful app (Stateful) | StatefulSet |
| One-off script or task | Job |
| Scheduled report or task | CronJob |
| Monitoring agent on every node | DaemonSet |
Step 6: Continuous Deployment (CD)
The CD process detects a new image in the Registry and automatically updates the Deployment in Kubernetes to use it. Kubernetes does the rest, performing a smooth Rolling Update.
- A CD tool like ArgoCD detects the new image.
- It updates the Deployment file with the new version.
- Kubernetes deploys the update gradually with no downtime.
Step 7: Application is Live!
The application is now running and managed by Kubernetes. Its role is not just to run, but to be a "guardian". It continuously monitors the app, restarts failed Pods (Self-Healing), and increases their number when needed (Auto-Scaling).
- Self-Healing ensures application stability.
- Auto-Scaling handles load changes.
- Monitoring tools track the health and performance of the application.
Kubernetes: The Conductor
This automated, flexible, and scalable process is made possible by Kubernetes. It's not just about running containers, but about managing them reliably at scale and orchestrating their entire lifecycle.