Dreadnot - deploy without dread

Dreadnot is a 'one click' deploy tool written in Node.js.

Dreadnot was heavily inspired by Etsy's Deployinator.

Configuration

Dreadnot loads its configuration from a javascript file:

exports.config = {
  // The name of this Dreadnot instance, used for display
  name: 'Example Dreadnot',

  // Each Dreadnot instance supports one environment such as 'dev', 'staging'
  // or 'production'
  env: 'staging',

  // The data root Dreadnot will use
  data_root: '/var/dreadnot',

  // Base URL to access dreadnot (used in IRC, email)
  default_url: 'http://example.com',

  // Dreadnot uses an htpasswd file (with support for md5 and sha1) for auth
  htpasswd_file: '/etc/dreadnot/htpasswd',

  // Each stack represents a code base that should be deployed to one or more regions
  stacks: {

    // For a stack named 'webapp', there should be a 'webapp.js' file in the
    // stacks directory
    webapp: {
      // What branch to look in for the latest revision of the code base
      tip: 'master',

      // How long to cache the latest revision of the code base
      tip_ttl: 120 * 1000,

      // What regions this stack should be deployed to
      regions: ['ord1'],

      // Stacks should implement dryrun for testing
      dryrun: true
    }
  },

  // The GitHub organization you provide is used to build URLs for your stacks
  github: {
    organization: 'racker'
  },

  // Plugins provide optional functionality such as notifications. Any plugins
  // that are not configured won't be used.
  plugins: {

    // An IRC notification plugin
    irc: {
      nick: 'staging-dreadnot',
      channels: {'irc.freenode.net': ['#public-channel', '#private-channel pass']}
    },
    
    // An email notification plugin
    email: {
      server: {
        user: 'staging-dreadnot@example.com',
        password: '',
        host: 'smtp.example.com',
        ssl: true
      },
      to: 'systems@example.com',
      from: 'staging-dreadnot@example.com'
    }
  }
};

Stacks

Dreadnot looks in a directory (by default ./stacks, but this can be changed from the command line) for "stack files". A stack file is simply a javascript file that exports

• A get_deployedRevision function which takes an object containing environment and region fields, and a callback taking (err, deployed_revision).
• A targets hash that maps target names to lists of task names. Currently, the only supported target is deploy which defaults to ['task_preDeploy', 'task_deploy', 'task_postDeploy'].
• One or more "task functions" whose names are prefixed with task_. Each task function takes:
  1. A "stack" object. The most useful fields on the stack are stackConfig which contains the config for this particular stack, and config which contains the global config.
  2. A "baton" object. Each task executed during a run of a given target receives the same baton object. By default, it contains a log field with methods such as debug, info, and error that can be used to log output to deployment log and web view.
  3. An "args" hash with dryrun, environment, region, revision and user, each of which is a string.
  4. A "callback" function that should be called without arguments on completion, or with a single error object if an error occurs.

Tasks

In the configuration used by Rackspace Cloud Monitoring, a deployment looks something like:

1. Build: verify that the requested revision has been successfully built and that all tests pass.
2. Prepare: remove the region being deployed from the load balancer rotation, redirecting all traffic to another region.
3. Execute: use a chef search to locate all servers in the region, then ssh to each in parallel to upgrade the code.
4. Validate: execute checks against each upgraded service to verify that it is functioning properly.
5. Restore: restore the region to the load balancer rotation.

Imporantly, Dreadnot knows nothing about the hosts to which it is deploying - if it did, we would have to modify our Dreadnot configuration every time we added or removed a machine from our environment. Instead, we rely on chef (although anything that knows about your servers will work) to give us an up-to-date list of all hosts in a given region. In smaller deployments it might be suitable to hardcode a list of hosts.

FAQ

Does Dreanot support SVN?

Dreanot supports Node.js - you can use any technology or topology that suits you, as long as you can find a library for it.

Running Dreadnot

	npm install dreadnot -g

Dreadnot takes a number of options on the command line. The defaults are:

  dreadnot -c ./local_settings.js -s ./stacks -p 8000

This will start dreadnot with the specified config file and stack directories, listening on port 8000.