Day-23 🐳 Dockerizing a 3-Tier MERN App & Diving into ITSM Tools

Source: Dev.to

Today was a massive step forward in my DevOps journey. I moved away from simply running containers individually and tackled Dockerizing a full 3‑tier MERN application (MongoDB, Express/Node, React).

🏗️ The Project: 3‑Tier Architecture

Instead of running npm start in three different terminals, I wanted to containerize the entire stack.

• Frontend: React (running in a container)
• Backend: Node.js/Express (API layer)
• Database: MongoDB (persistent storage)

🐙 Orchestration with Docker Compose

The real game‑changer today was using Docker Compose. Writing a docker‑compose.yml allowed me to define the lifecycle of all three containers in a single file.

• Defined services for the client, server, and database.
• Set up networking so they could talk to each other (using service names as hostnames).
• Configured volumes for data persistence.

Now bringing up the whole environment is just:

docker-compose up --build

🐛 The “Gotcha” Moment

It wouldn’t be a coding day without an error. Everything worked perfectly on my local setup, but the moment I spun up the container it crashed with a binary compatibility error.

The issue was that the COPY . . command was copying my local Windows‑based node_modules into the Linux container. Since esbuild and other binaries are OS‑specific, the Linux container couldn’t run the Windows binaries.

How I Resolved It

1. Created a .dockerignore file to explicitly exclude node_modules and .git.
2. Deleted the corrupted image.
3. Rebuilt the image using the --no-cache flag to ensure a completely fresh installation.

After updating the configuration, the containers communicated perfectly.

🏢 Beyond Code: ITSM Tools

While waiting for builds, I stepped back to learn about the “process” side of DevOps. I explored:

• Jira & Confluence: Tracking tasks and documentation.
• ServiceNow: Incident Management (handling outages) and Change Management (safely deploying updates).

Understanding how these tools fit into the CI/CD pipeline is crucial for working in enterprise environments.

🚀 What’s Next?

I have conquered Docker Compose. The natural next step? Orchestration at scale. Starting tomorrow, I’m diving into Kubernetes (K8s). Can’t wait to see how pods and services compare to what I did today.

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