Docker-compose.yml example for python web and redis service

ref from :https://docs.docker.com/compose/gettingstarted/

 Step 1: Python web app.py

import time

import redis
from flask import Flask

app = Flask(__name__)
cache = redis.Redis(host='redis', port=6379)


def get_hit_count():
    retries = 5
    while True:
        try:
            return cache.incr('hits')
        except redis.exceptions.ConnectionError as exc:
            if retries == 0:
                raise exc
            retries -= 1
            time.sleep(0.5)


@app.route('/')
def hello():
    count = get_hit_count()
    return 'Hello World! I have been seen {} times.\n'.format(count)

 Step 2: Python requirements.txt 

flask
redis

Step 3: Create a Dockerfile

FROM python:3.7-alpine
WORKDIR /code
ENV FLASK_APP app.py
ENV FLASK_RUN_HOST 0.0.0.0
RUN apk add --no-cache gcc musl-dev linux-headers
COPY requirements.txt requirements.txt  
RUN pip install -r requirements.txt
EXPOSE 5000
COPY . .
CMD ["flask", "run"]

Step 4: Edit the Compose file to add a bind mount

version: '3'
services:
  web:
    build: .
    ports:
      - "5000:5000"
    volumes:
      - .:/code
    environment:
      FLASK_ENV: development
  redis:
    image: "redis:alpine"

Step 5: (Re-)build and run the app with Compose on detached mode -d 

$  docker-compose up -d

composetest_web_1 is up-to-date

composetest_redis_1 is up-to-date

$  docker-compose ps

       Name                      Command               State           Ports         

-------------------------------------------------------------------------------------

composetest_redis_1   docker-entrypoint.sh redis ...   Up      6379/tcp              

composetest_web_1     flask run                        Up      0.0.0.0:5000->5000/tcp

$ docker-compose run web env

PATH=/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

HOSTNAME=2614983f7955

TERM=xterm

FLASK_ENV=development

LANG=C.UTF-8

GPG_KEY=0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D

PYTHON_VERSION=3.7.9

PYTHON_PIP_VERSION=20.2.2

PYTHON_GET_PIP_URL=https://github.com/pypa/get-pip/raw/5578af97f8b2b466f4cdbebe18a3ba2d48ad1434/get-pip.py

PYTHON_GET_PIP_SHA256=d4d62a0850fe0c2e6325b2cc20d818c580563de5a2038f917e3cb0e25280b4d1

FLASK_APP=app.py

FLASK_RUN_HOST=0.0.0.0

HOME=/root

Step 6: docker-Compose help

$ docker-compose --help

Define and run multi-container applications with Docker.

Usage:

  docker-compose [-f <arg>...] [options] [COMMAND] [ARGS...]

  docker-compose -h|--help

Options:

  -f, --file FILE             Specify an alternate compose file

                              (default: docker-compose.yml)

  -p, --project-name NAME     Specify an alternate project name

                              (default: directory name)

  -c, --context NAME          Specify a context name

  --verbose                   Show more output

  --log-level LEVEL           Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)

  --no-ansi                   Do not print ANSI control characters

  -v, --version               Print version and exit

  -H, --host HOST             Daemon socket to connect to

  --tls                       Use TLS; implied by --tlsverify

  --tlscacert CA_PATH         Trust certs signed only by this CA

  --tlscert CLIENT_CERT_PATH  Path to TLS certificate file

  --tlskey TLS_KEY_PATH       Path to TLS key file

  --tlsverify                 Use TLS and verify the remote

  --skip-hostname-check       Don't check the daemon's hostname against the

                              name specified in the client certificate

  --project-directory PATH    Specify an alternate working directory

                              (default: the path of the Compose file)

  --compatibility             If set, Compose will attempt to convert keys

                              in v3 files to their non-Swarm equivalent

  --env-file PATH             Specify an alternate environment file

Commands:

  build              Build or rebuild services

  config             Validate and view the Compose file

  create             Create services

  down               Stop and remove containers, networks, images, and volumes

  events             Receive real-time events from containers

  exec               Execute a command in a running container

  help               Get help on a command

  images             List images

  kill               Kill containers

  logs               View output from containers

  pause              Pause services

  port               Print the public port for a port binding

  ps                 List containers

  pull               Pull service images

  push               Push service images

  restart            Restart services

  rm                 Remove stopped containers

  run                Run a one-off command

  scale              Set number of containers for a service

  start              Start services

  stop               Stop services

  top                Display the running processes

  unpause            Unpause services

  up                 Create and start containers

  version            Show the Docker-Compose version information

If you started Compose with docker-compose up -d, stop your services once you’ve finished with them:

$ docker-compose stop

You can bring everything down, removing the containers entirely, with the down command. Pass --volumes to also remove the data volume used by the Redis container:

$ docker-compose down --volumes

At this point, you have seen the basics of how Compose works.