docker-spawn

Makes spawning docker servers as easy as require() in node.js.

This uses the docker REST API to spawn docker server images, to make servers easily available for node.js.

This removes the need to have a complex server installed, and you need only have a docker server, and then any server can be installed and quickly spawned using this module.

Typical use cases include repeatable unit testing with database servers, or removing the need to have a server (eg. mysql) installed in your development environment.

Example Usage

Spawn a mysql server

var spawn = require('docker-spawn');
 
// default boot2docker IP
var dockerhost = '172.18.42.1'
var dockerport = 4243;
 
// spawn a mysql server, and remove it when done
spawn(dockerhost, dockerport, {
   image: 'orchardup/mysql',
   ports: [3306],
  remove: true
}, work);
 
// now have an active mysql server, listening on exposed[0]
// the stop function is called to stop and remove the container image
function work(err, exposed, stop) {
  if (err) throw err;
  sequelize = new Sequelize('mysql', 'root', '', {
    dialect: 'mysql',
      host: dockerhost,
      port: exposed[0],
      pool: {
        handleDisconnects: true
      },
      logging: false
  });
  sequelize
    .authenticate()
    .done(function(err) {
      if (err) {
        // shut down the server and remove it (because 'remove' was true)
        stop(function () {
          throw err;
        });
      } else {
        sequelize.query('select * from user').done(function (err, data) {
          if (err) throw err;
          expect(data.length).to.equal(8);
 
          // shut down the server and remove it (because 'remove' was true)
          stop();
        });
      }
    });
}

API

spawn(dockerhost, [dockerport,] options, cb)

Spawns (and pulls the image if it doesn't exist) a new docker image and makes it available to node.

• dockerhost - the TCP hostname of your docker server. See the installation notes below about the easiest way to install a local docker server.
• dockerport - the TCP port of your docker server. If not provided, will assume port 4243.
• options - includes the following keys:
  • image - the name of a docker image (eg. orchardup/mysql) to run
  • ports - an Array of ports to expose. These will be mapped to dynamic ports like 49153 but returned to the node function through the exposedPorts argument in the callback.
  • remove - if set to true, then the server image will be removed when closed (Useful for temporary image creation - eg. unit tests, CI, etc)
• cb(err, exposedPorts, stop) - This callback get called after the spawn completes. The arguments are:
  • err - any error that was experienced.
  • exposedPorts - an array of the dynamically mapped ports. These are the actual ports that can be used to connect to the server. For example if the array [3306] was passed for a mysql server, then the exposedPorts array would contain something like [49173], and the mysql server would be listening on this port. NB: The spawn function also polls these ports by trying to connect to them, so you get called back once the socket is listening. Depending on the server, this may be enough for you to use the ports, or you may need to wait some more (eg. a wordpress HTTP server where nginx is working, but the database server is not ready yet).
  • stop - this is a function, that when called will stop the underlying docker container. If remove was set in the options object, then the container will removed onces it is stopped.

NB: If the docker image specified in options is not present in the docker server, then it will be pulled. This can take a long time based on the size of the image, and the speed of your connection, and is also more susceptible to failure (ie. is less deterministic). I recommend either doing a spawn.pull (see below), or simply a docker pull [image] from the command line to make sure the images are present before running spawn for the most reliable experience.

spawn.pull(dockerhost, [dockerport], image, cb)

Pulls a docker image.

This is a helper function to do the equivalent of docker pull [image].

It is useful if you want to make sure that all your docker images are present in your docker server before spawning them. For example, you might put this in your before() function in your unit tests to make sure that all your images are present before doing the unit tests.

Note, that pulling images can take a long time (minutes or more). So, tests may timeout. You might want to add this.timeout(0) if you're using mocha or the equivalent for your unit testing framework.

Pulling images is also more susceptible to failure, so you might just want to do a docker pull [image] from the command line to make sure that youre images are present for the most reliable and deterministic behaviour.

Installation

This module is installed via npm:

$ npm install docker-spawn

Installation of a Docker Server

This module requires a docker server listening on TCP port.

Recommended option: Use boot2docker

The easiest way to do this is to install boot2docker which will install a docker server in virtualbox on your local development machine.

boot2docker is a light-weight linux distribution optimized for fast startup, minimal memory footprint, and perfect for local development, and is officially endorsed by the docker team for local non-linux development.

For installation instructions, see the official page at: boot2docker

Official docker.io vagrant image

You can also use the official docker vagrant image.

But you'll need to configure the docker daemon to listen on port 4243, rather than just the internal unix socket which is on by default.

To do this, you'll need to change /etc/default/docker to have the following DOCKER_OPTS line:

DOCKER_OPTS="-H unix:///var/run/docker.sock -H tcp://0.0.0.0:4243 -api-enable-cors"

Then restart docker with:

$ sudo service docker restart

Official coreos vagrant image

You can also use the coreos vagrant image but you'll need to configure the docker daemon to listen on port 4243, rather than just on the internal unix socket.

Because it uses systemd, this requires a litle bit more work.

You'll need to create a new service file called /media/state/units/docker-local.service with the following contents:

[Service]
Type=simple
ExecStartPre=/usr/bin/systemctl kill docker.service
ExecStartPre=/bin/mount --make-rprivate /
ExecStart=/usr/bin/docker -d -H tcp://0.0.0.0:4243 -api-enable-cors -r=false

KillSignal=SIGKILL

[Install]
WantedBy=local.target

This will kill the default service and launch a new one that listens on port 4243.

You'll then need to reboot your coreos server to get the new docker service to run:

$ sudo reboot