Added a Supervisor process management example

docs/sources/examples/index.rst

@@ -24,3 +24,4 @@ to more substantial services like those which you might find in production.
    postgresql_service
    mongodb
    running_riak_service
+   using_supervisord

docs/sources/examples/using_supervisord.rst

@@ -0,0 +1,128 @@
+:title: Using Supervisor with Docker
+:description: How to use Supervisor process management with Docker
+:keywords: docker, supervisor, process management
+
+.. _using_supervisord:
+
+Using Supervisor with Docker
+============================
+
+.. include:: example_header.inc
+
+Traditionally a Docker container runs a single process when it is launched, for
+example an Apache daemon or a SSH server daemon. Often though you want to run
+more than one process in a container. There are a number of ways you can
+achieve this ranging from using a simple Bash script as the value of your
+container's ``CMD`` instruction to installing a process management tool.
+
+In this example we're going to make use of the process management tool,
+`Supervisor <http://supervisord.org/>`_, to manage multiple processes in our
+container. Using Supervisor allows us to better control, manage, and restart the
+processes we want to run. To demonstrate this we're going to install and manage both an
+SSH daemon and an Apache daemon.
+
+Creating a Dockerfile
+---------------------
+
+Let's start by creating a basic ``Dockerfile`` for our new image.
+
+.. code-block:: bash
+
+    FROM ubuntu:latest
+    MAINTAINER examples@docker.io
+    RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
+    RUN apt-get update
+    RUN apt-get upgrade -y
+
+Installing Supervisor
+---------------------
+
+We can now install our SSH and Apache daemons as well as Supervisor in our container.
+
+.. code-block:: bash
+
+    RUN apt-get install -y openssh-server apache2 supervisor
+    RUN mkdir -p /var/run/sshd
+    RUN mkdir -p /var/log/supervisor
+
+Here we're installing the ``openssh-server``, ``apache2`` and ``supervisor``
+(which provides the Supervisor daemon) packages. We're also creating two new
+directories that are needed to run our SSH daemon and Supervisor.
+
+Adding Supervisor's configuration file
+--------------------------------------
+
+Now let's add a configuration file for Supervisor. The default file is called
+``supervisord.conf`` and is located in ``/etc/supervisor/conf.d/``.
+
+.. code-block:: bash
+
+    ADD supervisord.conf /etc/supervisor/conf.d/supervisord.conf
+
+Let's see what is inside our ``supervisord.conf`` file.
+
+.. code-block:: bash
+
+    [supervisord]
+    nodaemon=true
+
+    [program:sshd]
+    command=/usr/sbin/sshd -D
+
+    [program:apache2]
+    command=/bin/bash -c "source /etc/apache2/envvars && /usr/sbin/apache2 -DFOREGROUND"
+
+The ``supervisord.conf`` configuration file contains directives that configure
+Supervisor and the processes it manages. The first block ``[supervisord]``
+provides configuration for Supervisor itself. We're using one directive,
+``nodaemon`` which tells Supervisor to run interactively rather than daemonize.
+
+The next two blocks manage the services we wish to control. Each block controls
+a separate process. The blocks contain a single directive, ``command``, which
+specifies what command to run to start each process.
+
+Exposing ports and running Supervisor
+-------------------------------------
+
+Now let's finish our ``Dockerfile`` by exposing some required ports and
+specifying the ``CMD`` instruction to start Supervisor when our container
+launches.
+
+.. code-block:: bash
+
+    EXPOSE 22 80
+    CMD ["/usr/bin/supervisord"]
+
+Here we've exposed ports 22 and 80 on the container and we're running the
+``/usr/bin/supervisord`` binary when the container launches.
+
+Building our container
+----------------------
+
+We can now build our new container.
+
+.. code-block:: bash
+
+    sudo docker build -t <yourname>/supervisord .
+
+Running our Supervisor container
+--------------------------------
+
+Once we've got a built image we can launch a container from it.
+
+.. code-block:: bash
+
+    sudo docker run -p 22 -p 80 -t -i <yourname>/supervisor
+    2013-11-25 18:53:22,312 CRIT Supervisor running as root (no user in config file)
+    2013-11-25 18:53:22,312 WARN Included extra file "/etc/supervisor/conf.d/supervisord.conf" during parsing
+    2013-11-25 18:53:22,342 INFO supervisord started with pid 1
+    2013-11-25 18:53:23,346 INFO spawned: 'sshd' with pid 6
+    2013-11-25 18:53:23,349 INFO spawned: 'apache2' with pid 7
+    . . .
+
+We've launched a new container interactively using the ``docker run`` command.
+That container has run Supervisor and launched the SSH and Apache daemons with
+it. We've specified the ``-p`` flag to expose ports 22 and 80. From here we can
+now identify the exposed ports and connect to one or both of the SSH and Apache
+daemons.
+