Method: MessageBus::Backends::Postgres#subscribe

Defined in:
lib/message_bus/backends/postgres.rb

#subscribe(channel, last_id = nil) {|message| ... } ⇒ nil

Subscribe to messages on a particular channel. Each message since the last ID specified will be delivered by yielding to the passed block as soon as it is available. This will block until subscription is terminated.

Parameters:

  • channel (String) —

    the name of the channel to which we should subscribe

  • last_id (#to_i) (defaults to: nil) —

    the channel-specific ID of the last message that the caller received on the specified channel

Yields:

  • (message) —

    a message-handler block

Yield Parameters:

Returns:

  • (nil)

Raises:

  • (ArgumentError) 


326
327
328
329
330
331
332
333
334
 
# File 'lib/message_bus/backends/postgres.rb', line 326

def subscribe(channel, last_id = nil)
  # trivial implementation for now,
  #   can cut down on connections if we only have one global subscriber
  raise ArgumentError unless block_given?

  global_subscribe(last_id) do |m|
    yield m if m.channel == channel
  end
end