docker getting started with docker compose

08 June 2015

info

  1. compose is a tool for defining and running complex apps with docker

  2. docs

    1. define app’s environment with a Dockerfile

       FROM python:2.7
 WORKDIR /code
 ADD requirements.txt /code/
 RUN pip install -r requirements.txt
 ADD . /code
 CMD python app.py

    2. define services that make up your app in docker-compose.yml

       web:
   build: .
   links:
    - db
   port:
    - "8000:8000"
 db:
   image: postgres

    3. run docker-compose up and compose will start and run your entire app

quick start

  1. install compose

    1. use commands

       $ curl -L https://github.com/docker/compose/releases/download/1.2.0/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
 $ chmod +x /usr/local/bin/docker-compose

    2. installed as a python package

       $ sudo pip install -U docker-compose

 $ docker-compose --version

  2. make a directory for the project

         $ mkdir composetest
     $ cd composetest

  3. create a simple web app use flask framework

         $ pico app.py
     from flask import Flask
     from redis import Redis
     import os
     app = Flask(__name__)
     redis = Redis(host='redis', port=6379)

     @app.route('/')
     def hello():
         redis.incr('hits')
         return 'hello world! I have been seen %s times.' % redis.get('hits')

     if __name__ == '__main__'
         app.run(host='0.0.0.0', debug=True)

  4. define python dependencies in requirements.txt

         $ pico requirements.txt
     flask
     redis

  5. create a docker image

    • specify how to build the image using Dockerfile

        $ pico Dockerfile
  FROM python:2.7
  ADD . /code
  WORKDIR /code
  RUN pip install -r requirements.txt

  6. define services

    • define a set of services using docker-compose.yml

        $ pico docker-compose.yml
  web:
    build: .
    command: python app.py
    ports:
     - '5000:5000'
    volumes:
     - .:/code
    links:
     - redis
  redis:
    image: redis

    • this define two services web and redis

        web:
      1. which is built from the Dockerfile
      2. run command python app.py inside the image
      3. forword exposed port 5000 on the container
      4. to port 5000 on the host machine
      5. connect up the redis service
      6. mount the current directory inside the container

  redis:
      which uses the public image redis

  7. build and run your app with compose

         $ docker-compose up

     Creating dockercompose_redis_1...
     Pulling image redis:latest...
     latest: Pulling from redis
     7a3e804ed6c0: Download complete
     b96d1548a24e: Download complete
     5ba9a5b9710f: Download complete
     37f07aacbfe5: Download complete
     ec7f3a6b5dc6: Download complete
     499b313c4d4e: Download complete
     e3c38490a53a: Download complete
     b508080bc4db: Download complete
     b5edc072cfec: Download complete
     41eb1212d9f4: Download complete
     2c010358721d: Download complete
     fb83dcd979bd: Download complete
     a1811b7b024f: Download complete
     05a396cb49e2: Download complete
     361283d1af1a: Download complete
     de77586468a2: Download complete
     0f3059144681: Download complete
     Status: Downloaded newer image for redis:latest
     Creating dockercompose_web_1...
     Building web...
     Step 0 : FROM python:2.7
     2.7: Pulling from python
     c9e3effdd23a: Pull complete
     24b3549417de: Pull complete
     3009dde7a8a5: Pull complete
     9da97b9166df: Pull complete
     a80d186674da: Pull complete
     c700c43ccd75: Pull complete
     26c01397e7df: Pull complete
     2abef589f374: Pull complete
     93d77aec17a0: Already exists
     39bb80489af7: Already exists
     df2a0347c9d0: Already exists
     7a3871ba15f8: Already exists
     a2703ed272d7: Already exists
     python:2.7: The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security.
     Digest: sha256:f8398c96bc62ee30fab45d44f8e1db2161b9a8e1f83e0fb0ae71b96950a3b329
     Status: Downloaded newer image for python:2.7
      ---> 93d77aec17a0
     Step 1 : ADD . /code
      ---> 9ee91686033a
     Removing intermediate container e61556a8e1e6
     Step 2 : WORKDIR /code
      ---> Running in e93e5c940b95
      ---> 9ee162f2324e
     Removing intermediate container e93e5c940b95
     Step 3 : RUN pip install -r requirements.txt
      ---> Running in 5a858f13c524
     Collecting flask (from -r requirements.txt (line 1))
       Downloading Flask-0.10.1.tar.gz (544kB)
     Collecting redis (from -r requirements.txt (line 2))
       Downloading redis-2.10.3.tar.gz (86kB)
     Collecting Werkzeug>=0.7 (from flask->-r requirements.txt (line 1))
       Downloading Werkzeug-0.10.4-py2.py3-none-any.whl (293kB)
     Collecting Jinja2>=2.4 (from flask->-r requirements.txt (line 1))
       Downloading Jinja2-2.7.3.tar.gz (378kB)
     Collecting itsdangerous>=0.21 (from flask->-r requirements.txt (line 1))
       Downloading itsdangerous-0.24.tar.gz (46kB)
     Collecting markupsafe (from Jinja2>=2.4->flask->-r requirements.txt (line 1))
       Downloading MarkupSafe-0.23.tar.gz
     Building wheels for collected packages: flask, redis, Jinja2, itsdangerous, markupsafe
       Running setup.py bdist_wheel for flask
       Stored in directory: /root/.cache/pip/wheels/d2/db/61/cb9b80526b8f3ba89248ec0a29d6da1bb6013681c930fca987
       Running setup.py bdist_wheel for redis
       Stored in directory: /root/.cache/pip/wheels/b4/82/09/7713ff9bc6f6a58e41b0a89433aed5d2293fd5868f76adef94
       Running setup.py bdist_wheel for Jinja2
       Stored in directory: /root/.cache/pip/wheels/b3/c0/62/8908d15b90a7de8bd15e2e6e5f5ba1398c0d9940d62a6bf8f5
       Running setup.py bdist_wheel for itsdangerous
       Stored in directory: /root/.cache/pip/wheels/97/c0/b8/b37c320ff57e15f993ba0ac98013eee778920b4a7b3ebae3cf
       Running setup.py bdist_wheel for markupsafe
       Stored in directory: /root/.cache/pip/wheels/94/a7/79/f79a998b64c1281cb99fa9bbd33cfc9b8b5775f438218d17a7
     Successfully built flask redis Jinja2 itsdangerous markupsafe
     Installing collected packages: Werkzeug, markupsafe, Jinja2, itsdangerous, flask, redis
     Successfully installed Jinja2-2.7.3 Werkzeug-0.10.4 flask-0.10.1 itsdangerous-0.24 markupsafe-0.23 redis-2.10.3
      ---> 39e8424b8205
     Removing intermediate container 5a858f13c524
     Successfully built 39e8424b8205
     Attaching to dockercompose_redis_1, dockercompose_web_1
     redis_1 | 1:C 09 Jun 02:26:47.968 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
     redis_1 |                 _._                                                  
     redis_1 |            _.-``__ ''-._                                             
     redis_1 |       _.-``    `.  `_.  ''-._           Redis 3.0.2 (00000000/0) 64 bit
     redis_1 |   .-`` .-```.  ```\/    _.,_ ''-._                                   
     redis_1 |  (    '      ,       .-`  | `,    )     Running in standalone mode
     redis_1 |  |`-._`-...-` __...-.``-._|'` _.-'|     Port: 6379
     redis_1 |  |    `-._   `._    /     _.-'    |     PID: 1
     redis_1 |   `-._    `-._  `-./  _.-'    _.-'                                   
     redis_1 |  |`-._`-._    `-.__.-'    _.-'_.-'|                                  
     redis_1 |  |    `-._`-._        _.-'_.-'    |           http://redis.io        
     redis_1 |   `-._    `-._`-.__.-'_.-'    _.-'                                   
     redis_1 |  |`-._`-._    `-.__.-'    _.-'_.-'|                                  
     redis_1 |  |    `-._`-._        _.-'_.-'    |                                  
     redis_1 |   `-._    `-._`-.__.-'_.-'    _.-'                                   
     redis_1 |       `-._    `-.__.-'    _.-'                                       
     redis_1 |           `-._        _.-'                                           
     redis_1 |               `-.__.-'                                               
     redis_1 | 
     redis_1 | 1:M 09 Jun 02:26:47.969 # Server started, Redis version 3.0.2
     redis_1 | 1:M 09 Jun 02:26:47.969 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
     redis_1 | 1:M 09 Jun 02:26:47.969 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
     redis_1 | 1:M 09 Jun 02:26:47.969 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
     redis_1 | 1:M 09 Jun 02:26:47.970 * DB loaded from disk: 0.000 seconds
     redis_1 | 1:M 09 Jun 02:26:47.970 * The server is now ready to accept connections on port 6379
     web_1   |  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
     web_1   |  * Restarting with stat
     web_1   | 192.168.59.3 - - [09/Jun/2015 02:27:38] "GET / HTTP/1.1" 200 -


     # if using boot2docker
     $ boot2docker ip
     192.168.59.103
     # will tell you its address

    • run your services in the background

        # -d flag for daemon mode
  $ docker-compose up -d

  # to see what is currently running
  $ docker-compose ps

  # run one-off commands for your services
  # to see what environment variables
  # are available to the web service
  $ docker-compose run web env

    • stop your services

        $ docker-compose stop
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