Demo Application Overview

To demonstrate how actual companies and organizations use Docker and Containers, I created a minimal 3-tier web application.

It has the following components:

• React front end
• NodeJS API
• Golang API
• Postgres Database

Each component is very minimal, but allows us to highlight the important aspects of containerizing and configuring the system.

Before we containerize it though, first we can explore the code and run it on our host system directly.

1. Setting up the Postgres Database

First, we'll run the Postgres database using the Docker run command. We will pass a POSTGRES_PASSWORD environment variable, use a volume mount to persist the data outside of the container, and publish port 5432 (the default port that Postgres runs on).

docker run -e POSTGRES_PASSWORD=foobarbaz -v pgdata:/var/lib/postgresql/data -p 5432:5432 -d postgres:15.1-alpine

2. Running the Node.js API

The Node.js API is located within the api-node subdirectory. First, ensure that you are using the correct version of Node (19.4 in this example). To install the dependencies, run npm install in the api-node directory.

To run the application, execute the following command:

DATABASE_URL=postgres://postgres:foobarbaz@localhost:5432/postgres npm run dev

This will start the API server, listening on port 3000. The API returns the current timestamp and an API key in the JSON response.

3. Running the Golang API

The Golang API is located within the api-golang subdirectory. First, set the GOPATH environment variable to the appropriate workspace directory. To install the dependencies, run go mod download in the api-golang directory.

To run the application, execute the following command:

DATABASE_URL=postgres://postgres:foobarbaz@localhost:5432/postgres go run main.go

This will start the API server, listening on port 8080. The API returns a similar response to the Node.js API, with the current timestamp and an API key in the JSON response.

4. Running the React Client

The React client is located within the client-react subdirectory. First, ensure that you are using the correct version of Node (19.4 in this example). To install the dependencies, run npm install in the client-react directory.

To run the application, execute the following command:

npm run dev

This will start the development server, listening on port 5173. The React app calls both the Node.js and Golang APIs and displays the responses.