calculate_memory_use.rb

module Puppet::Parser::Functions


  newfunction(:calculate_memory_use, :type => :rvalue, :doc => <<-'ENDHEREDOC') do |args|

    calculate_memory_use(use, reserved, minimum=0)

    [*use*]         How much memory should I use (of the non-reserved space left)
                    * Floating numbers smaller than 1 are interpreted as percentage.
                    * Anything else is used as size.

    [*reserved*] How much memory to keep for other processes.
                    * Floating numbers smaller than 1 are interpreted as percentage.
                    * Anything else is used as size.

    [*minimum*]     Required minimum size

    Examples:

      calculate_memory_use(0.4,512,64)

    @TODO: Documentation

  ENDHEREDOC

    raise Puppet::ParseError, "calculate_memory_use(): wrong number of arguments, need 2 or 3 " unless [2,3].include?(args.length)

    use = args.shift
    reserved = args.shift
    minimum = (args.shift or 0)

    unless use.respond_to?(:to_f)
      raise Puppet::ParseError, "calculate_memory_use(): unexpected argument type can not be converted to a number: use is a #{use.class.name}"
    end

    unless reserved.respond_to?(:to_f)
      raise Puppet::ParseError, "calculate_memory_use(): unexpected argument type can not be converted to a number: reserved_mb is a #{reserved.class.name}"
    end
    unless minimum.respond_to?(:to_f)
      raise Puppet::ParseError, "calculate_memory_use(): unexpected argument type can not be converted to a number: minimum is a #{minimum.class.name}"
    end

    use = use.to_f
    reserved = reserved.to_f
    minimum = minimum.to_f
    total_size_mb = lookupvar('memorysize_mb').to_f

    if reserved < 1.0
      reserved_mb = total_size_mb * reserved
    else
      reserved_mb = reserved
    end

    useable_size_mb = total_size_mb - reserved_mb

    if use < 1.0
      use_mb = useable_size_mb * use
    else
      use_mb = use
    end


    try_mb = [useable_size_mb, use_mb].min

    actual_use_mb = [minimum, try_mb].max
    #return {:total => total_size_mb,
    #        :reserved => reserved_mb,
    #        :minimum =>  minimum,
    #        :use_mb => use_mb,
    #        :trying_mb => try_mb,
    #        :actual_use_mb => actual_use_mb,
    #        :useable_mb => useable_size_mb}

    if actual_use_mb > useable_size_mb
      raise Puppet::ParseError, "calculate_memory_use(): insufficient free memory (#{useable_size_mb}) to provide the requested amount (#{actual_use_mb})"
    end

    actual_use_mb

  end

end