Random cron job minutes

random_crontab_minutes.rb

module Puppet::Parser::Functions
  newfunction(:random_crontab_minutes, :type => :rvalue) do |*arguments|
    #
    # This is to ensure that whenever we call this function from within
    # the Puppet manifest or alternatively form a template it will always
    # do the right thing ...
    #
    arguments = arguments.shift if arguments.first.is_a?(Array)

    raise Puppet::ParseError, "random_crontab_minutes(): Wrong number " +
      "of arguments given (#{arguments.size} for 2)" if arguments.size < 2

    job_name = arguments.shift

    raise Puppet::ParseError, 'random_crontab_minutes(): First argument ' +
      'requires a string type to work with' unless job_name.is_a?(String)

    host = arguments.shift

    raise Puppet::ParseError, 'random_crontab_minutes(): Second argument ' +
      'requires a string type to work with' unless host.is_a?(String)

    # This is probably impossible as Digest is part of the Ruby Core ...
    begin
      require 'digest/sha1'
    rescue LoadError
      raise Puppet::ParseError, 'random_crontab_minutes(): Unable to ' +
        'load Digest::SHA1 library.'
    end

    #
    # Pick a random number based on the job and host name.  This will yield
    # the same value for exactly the same combination of the job and host name.
    #
    sha1 = Digest::SHA1.new

    value = sha1.hexdigest(job_name + host).hex % 60

    # Minutes are from 0 to 59 inclusive ...
    value < 60 ? value : 59
  end
end

# vim: set ts=2 sw=2 et :