Class: Kanina::Subscription

Inherits:
Object
  • Object
show all
Extended by:
Logger
Defined in:
lib/kanina/subscription.rb

Overview

Kanina::Subscription allows you to automatically receive messages from RabbitMQ, and run a block of code upon receiving each new message. Queues and bindings are set up on the fly. Subscriptions are also eagerly loaded by Rails, so they're defined when the Rails environment is loaded. Example:

# app/messages/user_message.rb class UserSubscription < Kanina::Subscription subscribe(bind: "user.exchange") do |data| puts data end end

Messages are depacked from JSON, into plain old Ruby objects. If you use Kanina::Message to send messages, it automatically encapsulates messages into JSON to make the process easier.

Constant Summary

Constants included from Logger

Logger::DEFAULT_LOG_LEVEL

Class Method Summary collapse

Methods included from Logger

logger, say

Class Method Details

.channel ⇒ Bunny::Channel

Helper method to return the channel that Kanina::Server is talking on.

Returns:

  • (Bunny::Channel) 


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# File 'lib/kanina/subscription.rb', line 24

def channel
  Kanina::Server.channel or fail 'Kanina::Server.channel is not open'
end

.create_binding(name, durable: false) ⇒ Object

Ensures the named exchange exists, and binds the queue to it.

Parameters:

  • name (String) —

    The name of the exchange to bind the queue to.

  • durable (Boolean) (defaults to: false) —

    Optional, whether to make the exchange durable.



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# File 'lib/kanina/subscription.rb', line 57

def create_binding(name, durable: false)
  if name.present?
    ensure_exchange_exists(name, durable: durable)
    @queue.bind(name)
  end
end

.create_queue(name, durable: false) ⇒ Bunny::Queue

Creates the queue or attaches to the existing queue. This will also create a random queue if the queue supplied is an empty string.

Parameters:

  • name (String) —

    The name of the queue.

  • durable (Boolean) (defaults to: false) —

    Optional, false by default. Whether the queue should be durable or not.

Returns:

  • (Bunny::Queue) 


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# File 'lib/kanina/subscription.rb', line 50

def create_queue(name, durable: false)
  @queue = channel.queue(name, durable: durable)
end

.subscribe(queue: '', bind: nil, durable: false) {|data| ... } ⇒ Object

Begins subscribing to the specified queue (or binds to an exchange and sets up an anonymous queue). The block is called for every message received, and data is passed in as a plain Ruby hash.

Parameters:

  • queue (String) (defaults to: '') —

    Optional, the queue to watch.

  • bind (String) (defaults to: nil) —

    Optional, the exchange to bind to.

  • durable (Boolean) (defaults to: false) —

    Optional, whether to make the queue and exchange durable.

Yield Parameters:

  • data (HashWithIndifferentAccess) —

    The payload of the message, automatically turned into a hash.



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# File 'lib/kanina/subscription.rb', line 36

def subscribe(queue:'', bind:nil, durable:false, &blk)
  create_queue(queue, durable: durable)
  create_binding(bind, durable: durable)
  @queue.subscribe do |delivery_info, properties, body|
    yield format_data(body)
  end
end