PTT - Pneumatic Tube Transport

PTT - messaging based on RabbitMQ and some conventions. It's built on top of Bunny gem.

Conventions

Messages are JSON-encoded strings
Consumers decode JSON payload and call message handlers
Publisher uses just direct AMQP exchange (however it might change later)
By default rejected messages are not requeued.

Installation

Add this line to your application's Gemfile:

gem 'ptt'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ptt

Usage

First of all you should register message handlers. A handler object should respond to #call method. When consumer receives a message from RabbitMQ, it decodes JSON payload and passes decoded data to the designated handler using #call method.

# Message handler
class Handler
  def call(data)
    # process received data
    # ...
  end
end

# In this case `Handler#call` will be called each time when a new message comes
# from RabbitMQ with routing key `foo`
PTT.configure do |pneumatic_tube|
  pneumatic_tube.register_handler('foo', Handler.new)
end

When you need to send a message, just call PTT.publish. You have to provide data and routing key. PTT publisher will encode data to JSON format and will publish it to the exchange with given routing key.

data = { foo: 'bar' }

# JSON encoded data will be send to exchange with `bar` routing key
PTT.publish('bar', data)

In case you need to requeue rejected messages there are two option available:

Via environment variable: PTT_DEFAULT_RETRY=true. This will override the default requeue value for the whole project.
Per handler, example:

class CarefulHandler
  def call(json)
    # do some work
  end

  def requeue?(error)
    # computes result based on the given error or
    # any other internal logic, e.g. requeue on
    # specific exceptions, but do not requeue in other cases.
  end
end

class CarelessHandler
  def call(json)
    # do some work
  end

  def requeue?(_)
    # in case of any failure simply drop messages from
    # the queue and don't even try anything else.
    return false
  end
end

Testing

$ script/test

Contributing

Fork it ( https://github.com/[my-github-username]/ptt/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

pvcarrera / ptt