The Big Programming Thread - Page 985

global_state = {
	p1: {
		p1: False,
		p2: False
	},
	p2: {
		p1: False,
		p2: False
	}
}

global_state_of_p1{
	p1: {
		p1: True,
		p2: False
	},
	p2: {
		p1: False,
		p2: False
	}
}

global_state_of_p2{
	p1: {
		p1: True,
		p2: False
	},
	p2: {
		p1: True, //p2 knows that p1 heard the message since it's the sender.
		p2: True //p2 has also heard the message now
	}
}

global_state_of_p2{
	p1: {
		p1: True,
		p2: True
	},
	p2: {
		p1: True,
		p2: True
	}
}

payload = {
    msg: 'our message',
    origin: 1,
    state: [false, true, false, false]
}

module DistributedSystem
  Payload = Struct.new(:message, :origin)

  class Peer
    attr_reader :id, :payload, :others
    attr_accessor :broken

    def initialize(id, broken = false)
      @id = id
      @broken = broken
    end

    def process(payload)
      puts "Peer ##{id} processing payload from ##{payload.origin || 'external'}..."

      if payload_external?(payload)
        puts 'Rebroadcasting to other peers'

        payload.origin = id

        rebroadcast(payload).merge({ id => true }).sort.to_h
      else
        puts "Peer ##{id}#{broken ? ' not' : ''} acknowledging receival from ##{payload.origin}"

        acknowledge(payload)
      end
    end

    def others=(peers)
      @others = peers.select { |p| p.id != id }
    end

    private

    def payload_external?(payload)
      payload.origin.nil?
    end

    def rebroadcast(payload)
      others.each_with_object({}) do |peer, results|
        results[peer.id] = peer.process(payload)
      end
    end

    def acknowledge(payload)
      !broken
    end
  end
end

payload = DistributedSystem::Payload.new('Hello')
peers = (1..5).to_a.map { |id| DistributedSystem::Peer.new(id) }
peers.each { |peer| peer.others = peers }

random_peer = peers.sample

puts random_peer.process(payload)

puts '*' * 50

some_broken_peers = peers.map do |peer|
  peer.broken = true if peer.id.even?
  peer
end

payload = DistributedSystem::Payload.new('Hello')

random_working_peer = peers.select { |peer| peer.broken == false }.sample
puts random_working_peer.process(payload)

Peer #2 processing payload from #external...
Rebroadcasting to other peers
Peer #1 processing payload from #2...
Peer #1 acknowledging receival from #2
Peer #3 processing payload from #2...
Peer #3 acknowledging receival from #2
Peer #4 processing payload from #2...
Peer #4 acknowledging receival from #2
Peer #5 processing payload from #2...
Peer #5 acknowledging receival from #2
{1=>true, 2=>true, 3=>true, 4=>true, 5=>true}
**************************************************
Peer #5 processing payload from #external...
Rebroadcasting to other peers
Peer #1 processing payload from #5...
Peer #1 acknowledging receival from #5
Peer #2 processing payload from #5...
Peer #2 not acknowledging receival from #5
Peer #3 processing payload from #5...
Peer #3 acknowledging receival from #5
Peer #4 processing payload from #5...
Peer #4 not acknowledging receival from #5
{1=>true, 2=>false, 3=>true, 4=>false, 5=>true}