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Randika Madhushan Perera
Randika Madhushan Perera

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Docker Hands-On Part 06

#tutorial #aws #docker

06. Docker Container Networking

Introduction

The process of containerizing applications represents a significant leap forward in how we deploy and manage software. The Flask framework, popular for its simplicity and flexibility for web application development, is an excellent candidate for Dockerization. This transformative journey from a centralized server setup to a containerized deployment offers numerous advantages, including streamlined deployment processes, improved scalability, and enhanced isolation for development and production environments.

The Journey to Dockerize a Flask Application

The task at hand involves moving a Flask application, aptly named "Notes App," into a Docker container. This application, designed for employees to store notes on current projects, will benefit from the portability and efficiency that containers provide.

Step-by-Step Guide to Containerization

01. Initial Configuration:

Begin by writing the necessary configuration code, including a Dockerfile and .dockerignore file, to build a clean and efficient Docker image for the Notes App.

Step 01: Create Dokcerignore file

$ vim .dockerignore
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add below

# Exclude files .dockeringnore Dockerfile .gitignore Pipfile.lock migrations/
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Create Dockerfile and add below

# version 01 FROM python:3 ENV PYBASE /pybase ENV PYTHONUSERBASE $PYBASE ENV PATH $PYABASE/bin:$PATH #install pipenv RUN pip install pipenv WORKDIR /tmp COPY Pipfile . RUN pipenv lock RUN PIP_USER=1 PIP_IGNORE_INSTALLED=1 pipenv install -d --system --ignore-pipfile COPY . /app/notes WORKDIR /app/notes EXPOSE 80 CMD ["flask", "run", "--port=80", "--host=0.0.0.0"]
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Building the First Image:

With the Dockerfile in place, build the initial image version of the Notes App. This step includes setting up the database within a container derived from the first image, ensuring that the application's data layer is ready for use.

Step 02: Build the image and container

$ docker build -t notesapp:0.1 .
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Step 03: Create and run a container for postgres:12.1-alpine

$ docker pull postgres:12.1-alpine $ docker run -d --name notesdb postgres:12.1-alpine
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Step 04: Create a network and attach it to the bridge network

$ docker network create -d bridge notes
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Step 05: List the docker networks

$ docker network ls NETWORK ID NAME DRIVER SCOPE df7f5f15c7ab bridge bridge local 7405f25b96f6 host host local ee4c71834f71 none null local 14219a8cf079 notes bridge local
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Step 06: Run a container using the notesapp image and mount the migrations directory

$ docker run --rm -it --network notes -v /home/ec2-user/notes/migrations:/app/notes/migrations notesapp:0.1 bash
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Step 07:

# flask db migrate
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Running the Application:

Deploy the Notes App container to verify its functionality. During this phase, monitoring the logs for any issues, such as the application running in debug mode, is crucial. Debug mode is not suitable for production due to potential security and performance implications.
Enhancing for Production:

Address the debug mode issue by switching the Flask application to run on a more robust WSGI (Web Server Gateway Interface) server, such as Gunicorn. This change involves updating the environment variables, modifying the pip file to include Gunicorn, and adjusting the Dockerfile to execute Gunicorn instead of Flask directly.

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