Docker Exercise 01

Goal: You have a simple Python 2.7 (Flask) and Mongo app that allows users to enter messages and displays the last message entered. There are a couple of files in this directory that are REQUIRED by the app to work:

1) app.py is the flask app 
2) requirements.txt includes a list of Python packages required to run this app
3) templates directory for html templates used by app.py and
4) static directory for css files.

This app expects a MongoDB instance to be running in the background and listening to TCP PORT:27017. You can simply issue the following command to start a mongo db instance docker run -d -p 27017:27017 mongo:latest. The app is started with "python app.py" from the provided directory.

Exercises:

1. Dockerizing: Assuming a MongoDB instance is listening on localhost:27017, create a Dockerfile to dockerise this app with the following requirements:

   • Make sure you install python-pip and install required Python packages listed in requirements.txt(e.g pip install -r requirements.txt)
   • Make sure that container created from the Dockerfile image listens to TCP PORT 5000.
   • You may choose your preferred base image as long as the app works. Recommended one is 'python:2.7' image which comes with python-pip so you don't have to install it.
   • Make sure to build and push this image Docker Hub. e.g 'docker push <your_docker_hub_username>/dockerexercise:v1'.
   • Make sure to provide the Dockerfile in the Docker Hub repo long description section as well as inn the response to this exercise.

Success Criteria : When performing 'docker run -p 5000:5000 your_hub_username/dockerexercise:v1 ' on a host running MongoDB on port 27017, the app needs to be accessible on TCP PORT 5000. Dockerfile must be present in the repo's long description.

2. Deploying with Compose: Assuming docker-compose is installed on localhost, create a docker-compose.yml file to describe the web and db services to run the same app as in Exercise 1 with the following requirements:

   Note: As a pre-requisite for this exercise, you need to make the following changes to your app.py file: (-) client = MongoClient('localhost', 27017) (+) client = MongoClient('db', 27017) Then, you need to build and push a new version of your image with a v2 tag: docker push <your_docker_hub_username>/dockerexercise:v2

   • the service names are web and db.
   • web service needs to use the image that you created <your_docker_hub_username>/dockerexercise:v2.
   • web service needs to bind host port 5000 to container port 5000.
   • web service needs to have db's ip address dynamically added to its /etc/hosts with the alias of "db".
   • db service must use 'latest' image of the official mongo image.
   • db service must expose port 27017.
   • db service must be passed a command argument of "--smallfiles".

Success Criteria: when performing a 'docker-compose up' with the produced docker-compose.yml file, the app should be working and accessible on TCP PORT 5000. docker-compose.yml needs to be included in the response to this exercise.