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@@ -9,109 +9,137 @@ Python Web App
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.. include:: example_header.inc
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-The goal of this example is to show you how you can author your own
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-Docker images using a parent image, making changes to it, and then
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-saving the results as a new image. We will do that by making a simple
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-hello Flask web application image.
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+While using Dockerfiles is the preferred way to create maintainable
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+and repeatable images, its useful to know how you can try things out
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+and then commit your live changes to an image.
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-**Steps:**
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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
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+container, and then saving the results as a new image. We will do
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+that by making a simple 'hello world' Flask web application image.
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-.. code-block:: bash
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+Download the initial image
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+--------------------------
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+
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+Download the ``shykes/pybuilder`` Docker image from the ``http://index.docker.io``
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+registry.
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- sudo docker pull shykes/pybuilder
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+This image contains a ``buildapp`` script to download the web app and then ``pip install``
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+any required modules, and a ``runapp`` script that finds the ``app.py`` and runs it.
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-We are downloading the ``shykes/pybuilder`` Docker image
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+.. _`shykes/pybuilder`: https://github.com/shykes/pybuilder
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.. code-block:: bash
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- URL=http://github.com/shykes/helloflask/archive/master.tar.gz
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+ $ sudo docker pull shykes/pybuilder
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-We set a ``URL`` variable that points to a tarball of a simple helloflask web app
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+.. note:: This container was built with a very old version of docker
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+ (May 2013 - see `shykes/pybuilder`_ ), when the ``Dockerfile`` format was different,
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+ but the image can still be used now.
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-.. code-block:: bash
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+Interactively make some modifications
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+-------------------------------------
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- BUILD_JOB=$(sudo docker run -d -t shykes/pybuilder:latest /usr/local/bin/buildapp $URL)
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+We then start a new container running interactively using the image.
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+First, we set a ``URL`` variable that points to a tarball of a simple
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+helloflask web app, and then we run a command contained in the image called
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+``buildapp``, passing it the ``$URL`` variable. The container is
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+given a name ``pybuilder_run`` which we will use in the next steps.
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-Inside of the ``shykes/pybuilder`` image there is a command called
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-``buildapp``, we are running that command and passing the ``$URL`` variable
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-from step 2 to it, and running the whole thing inside of a new
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-container. The ``BUILD_JOB`` environment variable will be set with the new container ID.
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+While this example is simple, you could run any number of interactive commands,
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+try things out, and then exit when you're done.
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.. code-block:: bash
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- sudo docker attach -sig-proxy=false $BUILD_JOB
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+ $ sudo docker run -i -t -name pybuilder_run shykes/pybuilder bash
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+
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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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-While this container is running, we can attach to the new container to
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-see what is going on. The flag ``--sig-proxy`` set as ``false`` allows you to connect and
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-disconnect (Ctrl-C) to it without stopping the container.
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+Commit the container to create a new image
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+------------------------------------------
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-.. code-block:: bash
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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 now have 3 different
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+ways to refer to the container: name ``pybuilder_run``, short-id ``c8b2e8228f11``, or
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+long-id ``c8b2e8228f11b8b3e492cbf9a49923ae66496230056d61e07880dc74c5f495f9``.
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- sudo docker ps -a
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+.. code-block:: bash
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-List all Docker containers. If this container has already finished
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-running, it will still be listed here.
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+ $ sudo docker commit pybuilder_run /builds/github.com/shykes/helloflask/master
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+ c8b2e8228f11b8b3e492cbf9a49923ae66496230056d61e07880dc74c5f495f9
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-.. code-block:: bash
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- BUILD_IMG=$(sudo docker commit $BUILD_JOB _/builds/github.com/shykes/helloflask/master)
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+Run the new image to start the web worker
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+-----------------------------------------
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-Save the changes we just made in the container to a new image called
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-``_/builds/github.com/hykes/helloflask/master`` and save the image ID in
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-the ``BUILD_IMG`` variable name.
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+Use the new image to create a new container with
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+network port 5000 mapped to a local port
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.. code-block:: bash
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- WEB_WORKER=$(sudo docker run -d -p 5000 $BUILD_IMG /usr/local/bin/runapp)
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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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+
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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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-- **"$BUILD_IMG"** is the image we want to run the command inside of.
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- **/usr/local/bin/runapp** is the command which starts the web app.
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-Use the new image we just created and create a new container with
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-network port 5000, and return the container ID and store in the
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-``WEB_WORKER`` variable.
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-.. code-block:: bash
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+View the container logs
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+-----------------------
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- sudo docker logs $WEB_WORKER
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- * Running on http://0.0.0.0:5000/
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-
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-View the logs for the new container using the ``WEB_WORKER`` variable, and
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+View the logs for the new ``web_worker`` container and
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if everything worked as planned you should see the line ``Running on
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http://0.0.0.0:5000/`` in the log output.
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+To exit the view without stopping the container, hit Ctrl-C, or open another
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+terminal and continue with the example while watching the result in the logs.
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+
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.. code-block:: bash
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- WEB_PORT=$(sudo docker port $WEB_WORKER 5000 | awk -F: '{ print $2 }')
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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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+
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+
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+See the webapp output
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+---------------------
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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`` variable.
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+Access the web app using the ``curl`` binary. If everything worked as planned you
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+should see the line ``Hello world!`` inside of your console.
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+
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.. code-block:: bash
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+ $ WEB_PORT=$(sudo docker port web_worker 5000 | awk -F: '{ print $2 }')
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+
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# install curl if necessary, then ...
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- curl http://127.0.0.1:$WEB_PORT
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- Hello world!
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+ $ curl http://127.0.0.1:$WEB_PORT
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+ Hello world!
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-Access the web app using the ``curl`` binary. If everything worked as planned you
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-should see the line ``Hello world!`` inside of your console.
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-**Video:**
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+Clean up example containers and images
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+--------------------------------------
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+
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+.. code-block:: bash
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-See the example in action
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+ $ sudo docker ps --all
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+
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+List ``--all`` the Docker containers. If this container had already finished
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+running, it will still be listed here with a status of 'Exit 0'.
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+
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+.. code-block:: bash
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-.. raw:: html
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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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- <iframe width="720" height="400" frameborder="0"
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- sandbox="allow-same-origin allow-scripts"
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- srcdoc="<body><script type="text/javascript"
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- src="https://asciinema.org/a/2573.js"
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- id="asciicast-2573" async></script></body>">
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- </iframe>
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+And now stop the running web worker, and delete the containers, so that we can
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+then delete the images that we used.
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-Continue to :ref:`running_ssh_service`.
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Andy Rothfusz