Example Container Deployment

Conflicting Dependencies

Imagine this: Your server runs two applications. App X needs Python 3.10 & Debian 11, while App Y requires Python 3.12 and Debian 12. These conflicting dependencies can exist on the same server. That’s where containers come in.

Prerequisites

Ensure you have the following are prepared on your system:

• Install Git - for version control and cloning the repository.
• Install Docker - for containerizing and running the application locally.

Local Installation

Note

• This guide can be simplified to just a few commands. However, to help you better understand how to build and run a container step by step, this documentation provides a more detailed walkthrough.

Follow these steps to simulate the deployment of two applications with conflicting dependencies on your local machine.

1. Clone the Repository

Clone this repository to your local machine using Git:

git clone https://github.com/michaelact/example-container

This will create a directory named example-container containing the project files.

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2. Navigate to the Application Directory

This repository contains two applications: App X and App Y. Each application has its own directory with a Dockerfile, docker-compose.yml, and source code.

To work with App X, navigate to its directory:

cd example-container/appx/

To work with App Y, navigate to its directory:

cd example-container/appy/

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3. Build the Docker Image

Each application has its own Dockerfile, which defines how the application is containerized. To build the Docker image for the application, run:

For App X:

docker build --no-cache -t appx .

For App Y:

docker build --no-cache -t appy .

What this does:

• The docker build command reads the Dockerfile and creates a Docker image for the application.
• The -t flag tags the image with a name (appx or appy), making it easier to reference later.

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4. Verify the Docker Image

After building the image, you can verify that it was created successfully by listing all Docker images on your system:

docker images

Expected Output:

REPOSITORY   TAG       IMAGE ID       CREATED          SIZE
appx         latest    abcdef123456   10 seconds ago   925MB
appy         latest    789ghi101112   15 seconds ago   925MB

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5. Deploy the Application

Each application directory contains a docker-compose.yml file, which defines how the container should be run. To start the application, use Docker Compose:

docker compose up -d

What this does:

• The docker compose up command reads the docker-compose.yml file and starts the container.
• The -d flag runs the container in detached mode (in the background).

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6. Verify the Application is Running

To check if the application is running, use the following command:

docker ps

Expected Output:

CONTAINER ID   IMAGE   COMMAND          CREATED         STATUS         PORTS                    NAMES
abcdef123456   appx    "python app.py"  10 seconds ago  Up 9 seconds   0.0.0.0:5000->5000/tcp   appx_container
789ghi101112   appy    "python app.py"  15 seconds ago  Up 14 seconds  0.0.0.0:5001->5001/tcp   appy_container

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7. Test the Application

Once the containers are running, you can test the applications by accessing them in your browser or using curl:

For App X (Python 3.10):

curl http://localhost:5000

Expected Output:

Hello from App X (Python 3.10)!

For App Y (Python 3.12):

curl http://localhost:5001

Expected Output:

Hello from App Y (Python 3.12)!

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8. Stop the Application

When you’re done, you can stop the containers using Docker Compose:

docker compose down

What this does:

• Stops and removes the containers while preserving the Docker images.