Docker Compose for Dev

Slides

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Exercises

• Try it yourself #1
• Try it yourself #2
• Try it yourself #3
• Try it yourself #4
• Try it yourself #5
• Try it yourself #6

Note: By default, docker-compose will use the docker-compose.yml file in the current directory. You can specify a different .yml file with the -f option.

Try it yourself #1

With Docker Compose

• Run the following commands:

$ docker-compose -f docker-compose-1-intro.yml run dev
root@container:/cwd# pip install -r requirements.txt
root@container:/cwd# python app.py

• Did it work?
• What are we missing?

Try it yourself #2

Linking Redis

• Run the following commands:

$ docker-compose -f docker-compose-2-redis.yml run dev
root@container:/cwd# pip install -r requirements.txt
root@container:/cwd# python test.py
root@container:/cwd# python app.py

Browse http://<DOCKER_IP>:5000

• Can you reach your app?
• Why not?

Try it yourself #3

Exposing the Ports

• Run the following commands:

$ docker-compose -f docker-compose-3-ports.yml run --service-ports dev
root@container:/cwd# pip install -r requirements.txt
root@container:/cwd# python test.py
root@container:/cwd# python app.py

Browse http://<DOCKER_IP>:5000

• Does it work?
• How could we avoid installing the requirements every time?

Try it yourself #4

Cache Volume

• Run the following commands:

$ docker-compose -f docker-compose-4-cache.yml run --service-ports dev
root@container:/cwd# pip install -r requirements.txt
root@container:/cwd# python test.py
root@container:/cwd# python app.py

• Exit the container
• Try again without installing anything:

$ docker-compose -f docker-compose-4-cache.yml run --service-ports dev
root@container:/cwd# python test.py
root@container:/cwd# python app.py

• Does it work without installing the requirements every time?

Try it yourself #5

Using a helper image

• Run the following one-off commands:

# Install requirements
$ docker-compose -f docker-compose-5-helper.yml run --rm dev \
    pip install -r requirements.txt

# Run the tests
$ docker-compose -f docker-compose-5-helper.yml run --rm dev \
    python test.py
    
# Start the app
$ docker-compose -f docker-compose-5-helper.yml up

• What extra step happened here compared to the previous exercises?
• Can you see any other benefit from using a custom image?
  • hint: docker images | grep python

Try it yourself #6

Break the tests

• Run the tests

  • You can use ./auto test
  • What's the exit code?
  • hint: echo $? (0 is good, anything else is bad)

• Break one of the test

  • For example you can change == to != in one of the assert in test.py
  • Run the tests again
  • What's the exit code?

• Why is this useful for continuous integration?

• Change the default command to python test.py

  • Try docker-compose up