Class: Firehose::Server::Channel

Inherits:
Object
  • Object
show all
Defined in:
lib/firehose/server/channel.rb

Overview

Connects to a specific channel on Redis and listens for messages to notify subscribers.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(channel_key, redis = self.class.redis, subscriber = self.class.subscriber) ⇒ Channel

Returns a new instance of Channel.



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# File 'lib/firehose/server/channel.rb', line 15

def initialize(channel_key, redis=self.class.redis, subscriber=self.class.subscriber)
  @channel_key, @redis, @subscriber = channel_key, redis, subscriber
  @list_key, @sequence_key = Server.key(channel_key, :list), Server.key(channel_key, :sequence)
end

Instance Attribute Details

#channel_key ⇒ Object (readonly)

Returns the value of attribute channel_key.



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# File 'lib/firehose/server/channel.rb', line 5

def channel_key
  @channel_key
end

#list_key ⇒ Object (readonly)

Returns the value of attribute list_key.



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# File 'lib/firehose/server/channel.rb', line 5

def list_key
  @list_key
end

#redis ⇒ Object (readonly)

Returns the value of attribute redis.



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# File 'lib/firehose/server/channel.rb', line 5

def redis
  @redis
end

#sequence_key ⇒ Object (readonly)

Returns the value of attribute sequence_key.



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# File 'lib/firehose/server/channel.rb', line 5

def sequence_key
  @sequence_key
end

#subscriber ⇒ Object (readonly)

Returns the value of attribute subscriber.



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# File 'lib/firehose/server/channel.rb', line 5

def subscriber
  @subscriber
end

Class Method Details

.redis ⇒ Object 



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# File 'lib/firehose/server/channel.rb', line 7

def self.redis
  @redis ||= EM::Hiredis.connect
end

.subscriber ⇒ Object 



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# File 'lib/firehose/server/channel.rb', line 11

def self.subscriber
  @subscriber ||= Server::Subscriber.new(EM::Hiredis.connect)
end

Instance Method Details

#next_message(last_sequence = nil, options = {}) ⇒ Object 



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# File 'lib/firehose/server/channel.rb', line 20

def next_message(last_sequence=nil, options={})
  last_sequence = last_sequence.to_i

  deferrable = EM::DefaultDeferrable.new
  # TODO - Think this through a little harder... maybe some tests ol buddy!
  deferrable.errback {|e| EM.next_tick { raise e } unless [:timeout, :disconnect].include?(e) }

  # TODO: Use HSET so we don't have to pull 100 messages back every time.
  redis.multi
    redis.get(sequence_key).
      errback {|e| deferrable.fail e }
    redis.lrange(list_key, 0, Server::Publisher::MAX_MESSAGES).
      errback {|e| deferrable.fail e }
  redis.exec.callback do |(sequence, message_list)|
    Firehose.logger.debug "exec returned: `#{sequence}` and `#{message_list.inspect}`"
    sequence = sequence.to_i

    if sequence.nil? || (diff = sequence - last_sequence) <= 0
      Firehose.logger.debug "No message available yet, subscribing. sequence: `#{sequence}`"
      # Either this resource has never been seen before or we are all caught up.
      # Subscribe and hope something gets published to this end-point.
      subscribe(deferrable, options[:timeout])
    elsif last_sequence > 0 && diff < Server::Publisher::MAX_MESSAGES
      # The client is kinda-sorta running behind, but has a chance to catch
      # up. Catch them up FTW.
      # But we won't "catch them up" if last_sequence was zero/nil because
      # that implies the client is connecting for the 1st time.
      message = message_list[diff-1]
      Firehose.logger.debug "Sending old message `#{message}` and sequence `#{sequence}` to client directly. Client is `#{diff}` behind, at `#{last_sequence}`."
      deferrable.succeed message, last_sequence + 1
    else
      # The client is hopelessly behind and underwater. Just reset
      # their whole world with the lastest message.
      message = message_list[0]
      Firehose.logger.debug "Sending latest message `#{message}` and sequence `#{sequence}` to client directly."
      deferrable.succeed message, sequence
    end
  end.errback {|e| deferrable.fail e }

  deferrable
end

#unsubscribe(deferrable) ⇒ Object 



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# File 'lib/firehose/server/channel.rb', line 62

def unsubscribe(deferrable)
  subscriber.unsubscribe channel_key, deferrable
end