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Cover image for Process to containerize simple python web application.
Rahul Gautam
Rahul Gautam

Posted on • Updated on

Process to containerize simple python web application.

Today, We are going to discuss on containerizing a simple web application.

What is Container?

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Simply, Docker containers are like boxes that you can put things in. You can put anything you want in a container, and it will keep it safe and sound. You can put multiple things in one container, or you can have just one thing in a container. It's up to you!

Docker File

Commands that you use on your command line to build an image can be put together in a file. These text files are called Dockerfile. They read the instructions given by users and build images automatically.

Let's try making a Dockerfile that runs ubuntu and echos our string. To create a Dockerfile, you will require to begin your instruction using FROM where you assign a parent image, which is your main build. We will build an ubuntu image and display "This is a test" on our screen.

Creating a Docker File:

1) Let's Create a Dockerfile (You can use any text editor. We will be using vi).

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2) Now, let's add our command to pull the ubuntu image and echo the message.

FROM ubuntu
CMD echo "This is a test" 
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3) Now, let's execute our command automatically using the docker build command.

docker build . -t ubuntutest
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You can see the Dockerfile has been built.

4) Now, let's run our build.

docker run ubuntutest
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Dockerfile to containerize an application

We are going to use Dockerfile to containerize our simple application.

Also, A simple Django application(API) has been made, which shows json data that I randomly generated from mockaroo. If you want to use the code I am using here, You can find it on https://github.com/Gamerited/JsonDjango .

1) First, let's check if the application works on a local server.

python3 manage.py runserver
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It seems to be running fine. Our task is to get it to run in a docker container.

2)Now, Let's create a Dockerfile to put up our command. Our Dockerfile will look like this,

FROM python:3.11-rc-slim

ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1
RUN mkdir /code
WORKDIR /code
RUN pip install --upgrade pip
COPY requirements.txt /code/

RUN pip install -r requirements.txt
COPY . /code/

EXPOSE 8000

CMD ["python", "manage.py", "runserver", "0.0.0.0:8000"]
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Here,

  • We are using python (3.11-rc-slim).

  • We are also using two environment variables (PYTHONDONTWRITEBYTECODE and PYTHONUNBUFFERED). PYTHONDONTWRITEBYTECODE removes .pyc files from the container, and PYTHONUNBUFFERED buffers our output to make it look normal.

  • We now create directory name code and change our directory to code.

  • We now upgrade our pip to the latest version and copy requirements.txt files to our code directory so we can install all the requirements to run this application.

  • We now copy all the source code to the directory.

  • We now inform Docker that the container listens on port 8000 using EXPORT.

  • We now command our container to run the python application on port 8000.

Now let's run our application. For this process, first, we will use the docker build command.

docker build . -t pythonapi
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We are naming our container with the image as pythonapi using the tag (-t) argument.

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The build is completed. Now, let's run our docker application using the command,

docker run pythonapi
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You can see it is running.

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Let's visit http://0.0.0.0:8000/,

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Uh oh, We were Unable to connect . We could not view our application because we had not forwarded the port from the container to our local device. We have to add the -p argument to our command. It will look like this,

docker run -p 8000:8000 pythonapi
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Where the initial port is our local device's port and the port number following it is what port we want to forward from the container. Now, let's visit the application,

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Voila! Now you can see your simple application is currently running inside a container.

Thank you for reading this blog, next time we will be publishing the image to Docker Hub.

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