ac999a9cb2
Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
130 lines
4.5 KiB
Markdown
130 lines
4.5 KiB
Markdown
page_title: Python Web app example
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page_description: Building your own python web app using docker
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page_keywords: docker, example, python, web app
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# Python Web App
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Note
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- This example assumes you have Docker running in daemon mode. For
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more information please see [*Check your Docker
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install*](../hello_world/#running-examples).
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- **If you don’t like sudo** then see [*Giving non-root
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access*](../../installation/binaries/#dockergroup)
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While using Dockerfiles is the preferred way to create maintainable and
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repeatable images, its useful to know how you can try things out and
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then commit your live changes to an image.
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The goal of this example is to show you how you can modify your own
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Docker images by making changes to a running container, and then saving
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the results as a new image. We will do that by making a simple ‘hello
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world’ Flask web application image.
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## Download the initial image
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Download the `shykes/pybuilder` Docker image from
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the `http://index.docker.io` registry.
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This image contains a `buildapp` script to download
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the web app and then `pip install` any required
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modules, and a `runapp` script that finds the
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`app.py` and runs it.
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$ sudo docker pull shykes/pybuilder
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Note
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This container was built with a very old version of docker (May 2013 -
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see [shykes/pybuilder](https://github.com/shykes/pybuilder) ), when the
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`Dockerfile` format was different, but the image can
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still be used now.
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## Interactively make some modifications
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We then start a new container running interactively using the image.
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First, we set a `URL` variable that points to a
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tarball of a simple helloflask web app, and then we run a command
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contained in the image called `buildapp`, passing it
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the `$URL` variable. The container is given a name
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`pybuilder_run` which we will use in the next steps.
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While this example is simple, you could run any number of interactive
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commands, try things out, and then exit when you’re done.
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$ sudo docker run -i -t -name pybuilder_run shykes/pybuilder bash
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$$ URL=http://github.com/shykes/helloflask/archive/master.tar.gz
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$$ /usr/local/bin/buildapp $URL
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[...]
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$$ exit
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## Commit the container to create a new image
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Save the changes we just made in the container to a new image called
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`/builds/github.com/shykes/helloflask/master`. You
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now have 3 different ways to refer to the container: name
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`pybuilder_run`, short-id `c8b2e8228f11`
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.literal}, or long-id
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`c8b2e8228f11b8b3e492cbf9a49923ae66496230056d61e07880dc74c5f495f9`
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.literal}.
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$ sudo docker commit pybuilder_run /builds/github.com/shykes/helloflask/master
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c8b2e8228f11b8b3e492cbf9a49923ae66496230056d61e07880dc74c5f495f9
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## Run the new image to start the web worker
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Use the new image to create a new container with network port 5000
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mapped to a local port
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$ sudo docker run -d -p 5000 --name web_worker /builds/github.com/shykes/helloflask/master /usr/local/bin/runapp
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- **"docker run -d "** run a command in a new container. We pass "-d"
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so it runs as a daemon.
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- **"-p 5000"** the web app is going to listen on this port, so it
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must be mapped from the container to the host system.
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- **/usr/local/bin/runapp** is the command which starts the web app.
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## View the container logs
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View the logs for the new `web_worker` container and
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if everything worked as planned you should see the line
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`Running on http://0.0.0.0:5000/` in the log output.
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To exit the view without stopping the container, hit Ctrl-C, or open
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another terminal and continue with the example while watching the result
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in the logs.
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$ sudo docker logs -f web_worker
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* Running on http://0.0.0.0:5000/
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## See the webapp output
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Look up the public-facing port which is NAT-ed. Find the private port
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used by the container and store it inside of the `WEB_PORT`
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variable.
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Access the web app using the `curl` binary. If
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everything worked as planned you should see the line
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`Hello world!` inside of your console.
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$ WEB_PORT=$(sudo docker port web_worker 5000 | awk -F: '{ print $2 }')
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# install curl if necessary, then ...
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$ curl http://127.0.0.1:$WEB_PORT
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Hello world!
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## Clean up example containers and images
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$ sudo docker ps --all
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List `--all` the Docker containers. If this
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container had already finished running, it will still be listed here
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with a status of ‘Exit 0’.
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$ sudo docker stop web_worker
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$ sudo docker rm web_worker pybuilder_run
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$ sudo docker rmi /builds/github.com/shykes/helloflask/master shykes/pybuilder:latest
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And now stop the running web worker, and delete the containers, so that
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we can then delete the images that we used.
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