modules

Veterinarian modules

Veterinarian supports two types of modules:

• Checks - Used to determine the healthy state of a machine/service
• Notifications - Actions policies for changes in health checks

Checks

A check module is merely a ruby class with the required method "poll", which is expected to return the boolean "true" for healthy and "false" for unhealthy.

The "initialize" method for you check must (at least) support three named variables "ip", "hostname", and "log" (to be used for your logger facility), and a final catchall for optional params.

require 'logger'

class BasicCheck
  attr_accessor :log

  def initialize(ip, hostname, logger=Logger.new(STDOUT), params)
    self.log = logger
    self.ip = ip
    self.hostname = hostname
  end

  def poll
    return true
  end
end

(optional) You can include additional variables by configuring them as attributes in the plugin configuration section of the configuration yaml. These will be passed in to the "params" (Hash) final argument for your retrieval.

Notifications

A notification module is merely a ruby class with the required methods "healthy" and "unhealthy", which is called (upon health state change) when veterinarian determines it's appropriate to notify of state changes.

The "initialize" method for you check must (at least) support one named variables "log" (to be used for your logger facility), and a final catchall for optional params.

require 'logger'

class BasicNotify
  attr_accessor :log

  def initialize(logger=Logger.new(STDOUT), params)
    self.log = logger
  end

  def healthy(key, value = nil)
    puts ":) Healthy: #{key} -> #{value}"
  end

  def unhealthy(key)
    puts ":( Unhealthy: #{key}"
  end
end

(optional) You can include additional variables by configuring them as attributes in the plugin configuration section of the configuration yaml. These will be passed in to the "params" (Hash) final argument for your retrieval.

Configuration of modules

There are two module-related sections of the config (yaml) aptly dubbed "checks" and "notifications". You include (as part of the module array - in yaml) the class name of your module.

checks:
  BasicCheck:
notifications:
  BasicNotify:

You can then include any additional attributes, like we require with the zookeeper notification module, as seen here:

notifications:
  ZkNode:
    connect_string: 127.0.0.1:2181
    parent_dir    : /webs

In this examples, the "params" attribute passed to the ZkNode constructor will offer the following values:

params['connect_string']
params['parent_dir']