Carnivore

Eat messages, rule the world.

Purpose

Slim library to consume messages. Sources are defined and callbacks are registered to defined sources. Sources feed messages to callback workers asynchronously and stuff gets done. Super simple!

Usage

1. Build a source
2. Add callbacks
3. Profit!

require 'carnivore'
Carnivore.configure do
  src = Carnivore::Source.build(:type => :test, :args => {})
  src.add_callback(:print_message) do |msg|
    puts "Received message: #{msg}"
  end
end.start!

Advanced Usage

Under the hood, callbacks are built into Carnivore::Callback instances. This class can be subclassed and provided directly instead of a simple block. This has the added bonus of being able to define the number of worker instances to be created for the callback (blocks only get 1):

require 'carnivore'

class CustomCallback < Carnivore::Callback

  self.workers = 5

  def setup
    info "Custom callback setup called!"
  end

  def execute(message)
    info "GOT MESSAGE: #{message[:message]} - source: #{message[:source]} - instance: #{self}"
  end
end

Carnivore.configure do
  s = Carnivore::Source.build(:type => :test, :args => {})
  s.add_callback(:printer, CustomCallback)
end.start!

Block execution

It is important to note that when providing blocks they will lose all reference to the scope in which they are defined. This is due to how Callback is implemented and is by design. Simply ensure that blocks are fully autonomous and everything will be great.

Example (bad):

Carnivore.configure do
  my_inst = AwesomeSauce.new
  src = Source.build(:type => :test, :args => {})
  src.add_callback(:print_message) do |msg|
    my_inst.be_awesome!
    puts "Received message: #{msg}"
  end
end.start!

Example (good):

Carnivore.configure do
  src = Source.build(:type => :test, :args => {})
  src.add_callback(:print_message) do |msg|
    my_inst = AwesomeSauce.new
    my_inst.be_awesome!
    puts "Received message: #{msg}"
  end
end.start!

So, does that mean a new AwesomeSauce instance will be created on every message processed? Yes, yes it does. However, the block at runtime is no longer really a block, so lets keep that instance around so it can be reused:

Example (more gooder):

Carnivore.configure do
  src = Source.build(:type => :test, :args => {})
  src.add_callback(:print_message) do |msg|
    unless(@my_inst)
      @my_inst = AwesomeSauce.new
    end
    @my_inst.be_awesome!
    puts "Received message: #{msg}"
  end
end.start!

Info

• Repository: https://github.com/carnivore-rb/carnivore
• IRC: Freenode @ #carnivore