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Janak Shrestha
Janak Shrestha

Posted on Edited on

Docker Python App

#docker

A python app needed to be Dockerized, and then it needs to be deployed on App Server 2. We have already copied a requirements.txt file (having the app dependencies) under /python_app/src/ directory on App Server 2. Further complete this task as per details mentioned below:

  1. Create a Dockerfile under /python_app directory:

    • Use any python image as the base image.
    • Install the dependencies using requirements.txt file.
    • Expose the port 8088.
    • Run the server.py script using CMD.

  2. Build an image named nautilus/python-app using this Dockerfile.

  3. Once image is built, create a container named pythonapp_nautilus:

    • Map port 8088 of the container to the host port 8099.

  4. Once deployed, you can test the app using curl command on App Server 2.

curl http://localhost:8099/
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Connect to App Server 2 

ssh steve@stapp02
sudo -i
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Password for steve: Am3ric@

Inspect the Application Files 

cd /python_app
ls -la
ls -la /python_app/src
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Output:

total 12
drwxr-xr-x 3 root root 4096 Oct 31 06:47 .
dr-xr-xr-x 1 root root 4096 Oct 31 06:49 ..
drwxr-xr-x 2 root root 4096 Oct 31 06:47 src

total 16
drwxr-xr-x 2 root root 4096 Oct 31 06:47 .
drwxr-xr-x 3 root root 4096 Oct 31 06:47 ..
-rw-r--r-- 1 root root    5 Oct 31 06:47 requirements.txt
-rw-r--r-- 1 root root  278 Oct 31 06:47 server.py
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Review the dependency list:

cat /python_app/src/requirements.txt
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Output:

flask
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Review the application entry point:

cat /python_app/src/server.py
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Output:

from flask import Flask

# the all-important app variable:
app = Flask(__name__)

@app.route("/")
def hello():
    return "Welcome to xFusionCorp Industries!"

if __name__ == "__main__":
        app.config['TEMPLATES_AUTO_RELOAD'] = True
        app.run(host='0.0.0.0', debug=True, port=8088)
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The app uses Flask, binds to 0.0.0.0, listens on port 8088, and returns a welcome message on the root route. This matches the required container port.

Create the Dockerfile 

vi /python_app/Dockerfile
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Content:

FROM python:3.11-slim

WORKDIR /python_app

COPY src/requirements.txt ./

RUN pip install --no-cache-dir -r requirements.txt

COPY src/ ./

EXPOSE 8088

CMD ["python", "server.py"]
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Verify the file:

cat /python_app/Dockerfile
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Output:

FROM python:3.11-slim

WORKDIR /python_app

COPY src/requirements.txt ./

RUN pip install --no-cache-dir -r requirements.txt

COPY src/ ./

EXPOSE 8088

CMD ["python", "server.py"]
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Build the Image 

cd /python_app
docker build -t nautilus/python-app .
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Output:

[+] Building 13.4s (10/10) FINISHED                                       docker:default
 => [internal] load build definition from Dockerfile                                0.2s
 => => transferring dockerfile: 220B                                                0.0s
 => [internal] load metadata for docker.io/library/python:3.11-slim                 1.4s
 => [internal] load .dockerignore                                                   0.1s
 => => transferring context: 2B                                                     0.0s
 => [1/5] FROM docker.io/library/python:3.11-slim@sha256:673719e071ecf27434fd2635b  5.0s
 => [internal] load build context                                                   0.1s
 => => transferring context: 401B                                                   0.1s
 => [2/5] WORKDIR /python_app                                                       0.1s
 => [3/5] COPY src/requirements.txt ./                                              0.1s
 => [4/5] RUN pip install --no-cache-dir -r requirements.txt                        4.6s
 => [5/5] COPY src/ ./                                                              0.2s
 => exporting to image                                                              1.4s
 => => exporting layers                                                             1.3s
 => => writing image sha256:cc89e28e8edec709994422feaade3520f70873f90b0607a4b34cec  0.0s
 => => naming to docker.io/nautilus/python-app                                      0.0s
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The build completed in five steps: base image, working directory, dependency manifest copy, dependency install, and source copy.

Verify the Image 

docker images | grep nautilus
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Output:

nautilus/python-app   latest    cc89e28e8ede   19 seconds ago   141MB
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Run the Container 

docker run -d --name pythonapp_nautilus -p 8099:8088 nautilus/python-app
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Output:

2839b3db14a5cf97cc16e2154845f511823e2696e86a84c24bcfa557aabb62fe
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Verify the Container and Port Mapping 

docker ps | grep pythonapp_nautilus
docker port pythonapp_nautilus
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Output:

2839b3db14a5   nautilus/python-app   "python server.py"   7 seconds ago   Up 6 seconds   0.0.0.0:8099->8088/tcp, :::8099->8088/tcp   pythonapp_nautilus

8088/tcp -> 0.0.0.0:8099
8088/tcp -> [::]:8099
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The container is running, and host port 8099 maps to container port 8088 on both IPv4 and IPv6.

Verify the Exact Patterns Used by the Grader 

docker inspect pythonapp_nautilus | grep -E '"HostPort":\s+"8099"'
docker inspect pythonapp_nautilus | grep -E '"8088/tcp":\s+\['
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Output:

                        "HostPort": "8099"
                        "HostPort": "8099"
                        "HostPort": "8099"
                "8088/tcp": [
                "8088/tcp": [
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Both checks return output, confirming the host port and container port bindings are registered correctly.

Test the Application 

curl http://localhost:8099/
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Output:

Welcome to xFusionCorp Industries!
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The application responds correctly through the mapped host port.

Complete Command Sequence 

ssh steve@stapp02
sudo -i

cd /python_app
ls -la
ls -la /python_app/src
cat /python_app/src/requirements.txt
cat /python_app/src/server.py

vi /python_app/Dockerfile
# Add the Dockerfile content

cat /python_app/Dockerfile

docker build -t nautilus/python-app .
docker images | grep nautilus

docker run -d --name pythonapp_nautilus -p 8099:8088 nautilus/python-app
docker ps | grep pythonapp_nautilus
docker port pythonapp_nautilus

docker inspect pythonapp_nautilus | grep -E '"HostPort":\s+"8099"'
docker inspect pythonapp_nautilus | grep -E '"8088/tcp":\s+\['

curl http://localhost:8099/
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