Method: AMQP::Channel#direct

Defined in:

lib/amqp/channel.rb

#direct(name = 'amq.direct', opts = {}, &block) ⇒ Exchange

Defines, intializes and returns a direct Exchange instance.

Learn more about direct exchanges in Exchange class documentation.

Examples:

Using default pre-declared direct exchange and no callbacks (pseudo-synchronous style)

# an exchange application A will be using to publish updates
# to some search index
exchange = channel.direct("index.updates")

# In the same (or different) process declare a queue that broker will
# generate name for, bind it to aforementioned exchange using method chaining
queue    = channel.queue("").
                   # queue will be receiving messages that were published with
                   # :routing_key attribute value of "search.index.updates"
                   bind(exchange, :routing_key => "search.index.updates").
                   # register a callback that will be run when messages arrive
                   subscribe { |header, message| puts("Received #{message}") }

# now publish a new document contents for indexing,
# message will be delivered to the queue we declared and bound on the line above
exchange.publish(document.content, :routing_key => "search.index.updates")

Instantiating a direct exchange using #direct with a callback

AMQP.connect do |connection|
  AMQP::Channel.new(connection) do |channel|
    channel.direct("email.replies_listener") do |exchange, declare_ok|
      # by now exchange is ready and waiting
    end
  end
end

Parameters:

• name (String) (defaults to: 'amq.direct') —

  (amq.direct) Exchange name.

• opts (Hash) (defaults to: {}) —

  a customizable set of options

Options Hash (opts):

• :passive (Boolean) — default: false —

  If set, the server will not create the exchange if it does not already exist. The client can use this to check whether an exchange exists without modifying the server state.

• :durable (Boolean) — default: false —

  If set when creating a new exchange, the exchange will be marked as durable. Durable exchanges and their bindings are recreated upon a server restart (information about them is persisted). Non-durable (transient) exchanges do not survive if/when a server restarts (information about them is stored exclusively in RAM).

• :auto_delete (Boolean) — default: false —

  If set, the exchange is deleted when all queues have finished using it. The server waits for a short period of time before determining the exchange is unused to give time to the client code to bind a queue to it.

• :internal (Boolean) — default: default false —

  If set, the exchange may not be used directly by publishers, but only when bound to other exchanges. Internal exchanges are used to construct wiring that is not visible to applications. This is a RabbitMQ-specific extension.

• :nowait (Boolean) — default: true —

  If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception.

Returns:

• (Exchange)

Raises:

• (AMQP::Error) —

  Raised when exchange is redeclared with parameters different from original declaration.

• (AMQP::Error) —

  Raised when exchange is declared with :passive => true and the exchange does not exist.

See Also:

• #default_exchange
• Exchange
• Exchange#initialize
• AMQP 0.9.1 specification (Section 3.1.3.1)

# File 'lib/amqp/channel.rb', line 372

def direct(name = 'amq.direct', opts = {}, &block)
  if exchange = find_exchange(name)
    extended_opts = Exchange.add_default_options(:direct, name, opts, block)

    validate_parameters_match!(exchange, extended_opts)

    block.call(exchange) if block
    exchange
  else
    register_exchange(Exchange.new(self, :direct, name, opts, &block))
  end
end