mirror of https://github.com/docker/compose.git
192 lines
6.2 KiB
Markdown
192 lines
6.2 KiB
Markdown
<!--[metadata]>
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+++
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title = "Getting Started"
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description = "Getting started with Docker Compose"
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keywords = ["documentation, docs, docker, compose, orchestration, containers"]
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[menu.main]
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parent="workw_compose"
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weight=-85
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+++
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<![end-metadata]-->
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# Getting Started
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On this page you build a simple Python web application running on Docker Compose. The
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application uses the Flask framework and increments a value in Redis. While the
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sample uses Python, the concepts demonstrated here should be understandable even
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if you're not familiar with it.
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## Prerequisites
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Make sure you have already
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[installed both Docker Engine and Docker Compose](install.md). You
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don't need to install Python, it is provided by a Docker image.
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## Step 1: Setup
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1. Create a directory for the project:
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$ mkdir composetest
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$ cd composetest
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2. With your favorite text editor create a file called `app.py` in your project
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directory.
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from flask import Flask
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from redis import Redis
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app = Flask(__name__)
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redis = Redis(host='redis', port=6379)
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@app.route('/')
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def hello():
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redis.incr('hits')
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return 'Hello World! I have been seen %s times.' % redis.get('hits')
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if __name__ == "__main__":
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app.run(host="0.0.0.0", debug=True)
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3. Create another file called `requirements.txt` in your project directory and
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add the following:
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flask
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redis
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These define the applications dependencies.
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## Step 2: Create a Docker image
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In this step, you build a new Docker image. The image contains all the
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dependencies the Python application requires, including Python itself.
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1. In your project directory create a file named `Dockerfile` and add the
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following:
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FROM python:2.7
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ADD . /code
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WORKDIR /code
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RUN pip install -r requirements.txt
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CMD python app.py
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This tells Docker to:
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* Build an image starting with the Python 2.7 image.
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* Add the current directory `.` into the path `/code` in the image.
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* Set the working directory to `/code`.
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* Install the Python dependencies.
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* Set the default command for the container to `python app.py`
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For more information on how to write Dockerfiles, see the [Docker user guide](/engine/tutorials/dockerimages.md#building-an-image-from-a-dockerfile) and the [Dockerfile reference](/engine/reference/builder.md).
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2. Build the image.
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$ docker build -t web .
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This command builds an image named `web` from the contents of the current
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directory. The command automatically locates the `Dockerfile`, `app.py`, and
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`requirements.txt` files.
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## Step 3: Define services
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Define a set of services using `docker-compose.yml`:
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1. Create a file called docker-compose.yml in your project directory and add
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the following:
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version: '2'
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services:
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web:
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build: .
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ports:
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- "5000:5000"
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volumes:
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- .:/code
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depends_on:
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- redis
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redis:
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image: redis
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This Compose file defines two services, `web` and `redis`. The web service:
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* Builds from the `Dockerfile` in the current directory.
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* Forwards the exposed port 5000 on the container to port 5000 on the host machine.
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* Mounts the project directory on the host to `/code` inside the container allowing you to modify the code without having to rebuild the image.
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* Links the web service to the Redis service.
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The `redis` service uses the latest public [Redis](https://registry.hub.docker.com/_/redis/) image pulled from the Docker Hub registry.
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## Step 4: Build and run your app with Compose
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1. From your project directory, start up your application.
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$ docker-compose up
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Pulling image redis...
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Building web...
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Starting composetest_redis_1...
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Starting composetest_web_1...
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redis_1 | [8] 02 Jan 18:43:35.576 # Server started, Redis version 2.8.3
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web_1 | * Running on http://0.0.0.0:5000/
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web_1 | * Restarting with stat
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Compose pulls a Redis image, builds an image for your code, and start the
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services you defined.
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2. Enter `http://0.0.0.0:5000/` in a browser to see the application running.
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If you're using Docker on Linux natively, then the web app should now be
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listening on port 5000 on your Docker daemon host. If `http://0.0.0.0:5000`
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doesn't resolve, you can also try `http://localhost:5000`.
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If you're using Docker Machine on a Mac, use `docker-machine ip MACHINE_VM` to get
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the IP address of your Docker host. Then, `open http://MACHINE_VM_IP:5000` in a
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browser.
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You should see a message in your browser saying:
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`Hello World! I have been seen 1 times.`
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3. Refresh the page.
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The number should increment.
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## Step 5: Experiment with some other commands
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If you want to run your services in the background, you can pass the `-d` flag
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(for "detached" mode) to `docker-compose up` and use `docker-compose ps` to
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see what is currently running:
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$ docker-compose up -d
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Starting composetest_redis_1...
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Starting composetest_web_1...
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$ docker-compose ps
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Name Command State Ports
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-------------------------------------------------------------------
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composetest_redis_1 /usr/local/bin/run Up
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composetest_web_1 /bin/sh -c python app.py Up 5000->5000/tcp
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The `docker-compose run` command allows you to run one-off commands for your
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services. For example, to see what environment variables are available to the
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`web` service:
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$ docker-compose run web env
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See `docker-compose --help` to see other available commands. You can also install [command completion](completion.md) for the bash and zsh shell, which will also show you available commands.
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If you started Compose with `docker-compose up -d`, you'll probably want to stop
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your services once you've finished with them:
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$ docker-compose stop
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At this point, you have seen the basics of how Compose works.
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## Where to go next
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- Next, try the quick start guide for [Django](django.md),
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[Rails](rails.md), or [WordPress](wordpress.md).
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- [Explore the full list of Compose commands](./reference/index.md)
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- [Compose configuration file reference](compose-file.md)
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