Initial commit.

.gitignore

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+*.gem
+*.rbc
+.bundle
+.config
+.yardoc
+Gemfile.lock
+InstalledFiles
+_yardoc
+coverage
+doc/
+lib/bundler/man
+pkg
+rdoc
+spec/reports
+test/tmp
+test/version_tmp
+tmp
+.DS_Store

.yardopts

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+--markup=markdown
+--charset=utf-8
+lib/**/*.rb

Gemfile

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+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in raft.gemspec
+gemspec
+
+gem 'celluloid', git: 'http://github.com/celluloid/celluloid'
+
+group :docs do
+  gem 'yard'
+  gem 'redcarpet'
+end

LICENSE

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+Copyright (c) 2013 Alexander Flatter
+
+MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# Raft
+
+TODO: Write a gem description
+
+## Installation
+
+Add this line to your application's Gemfile:
+
+    gem 'raft'
+
+And then execute:
+
+    $ bundle
+
+Or install it yourself as:
+
+    $ gem install raft
+
+## Usage
+
+TODO: Write usage instructions here
+
+## Contributing
+
+1. Fork it
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Added some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create new Pull Request

Rakefile

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+#!/usr/bin/env rake
+require "bundler/gem_tasks"

lib/raft.rb

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+require "raft/version"
+
+module Raft
+  # Your code goes here...
+end

lib/raft/log.rb

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+require 'forwardable'
+require 'raft'
+
+# See Section 5.3.
+class Raft::Log
+  extend Forwardable
+
+  def_delegators :entries, :[]
+
+  class Entry
+    # @return [Fixnum] When the entry was received by the leader.
+    attr_accessor :term
+
+    # @return [Object] A replicated state machine command.
+    attr_accessor :command
+
+    # @return [Boolean]
+    attr_accessor :committed
+
+    def committed?
+
+    end
+  end
+
+  # @return [Array<Entry>] The log's entries.
+  attr_accessor :entries
+
+  def initialize
+    self.entries = []
+  end
+
+  def append(prev_log_index, prev_log_term, new_entries)
+    if validate(prev_log_index, prev_log_term)
+      # Remove all entries after the previous one.
+      remove_starting_with(prev_log_index + 1)
+      entries.concat(new_entries)
+
+      true
+    else
+      false
+    end
+  end
+
+  def last_index
+    entries.size - 1
+  end
+
+  def last_term
+    entry = entries.last
+    entry ? entry.term : -1
+  end
+
+  def complete?(other_term, other_index)
+    (other_term > last_term) || (other_term == last_term && other_index >= last_index)
+  end
+
+  protected
+
+  def validate(index, term)
+    entry = entries[index]
+    entry && entry.term == term
+  end
+
+  def remove_starting_with(index)
+    entries.slice!(index..-1)
+  end
+end

lib/raft/node.rb

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+# encoding: utf-8
+
+require 'celluloid/zmq'
+require 'raft/rpc'
+require 'raft/log'
+
+class Raft::Node
+  require 'raft/node/states'
+
+  include Celluloid::ZMQ
+  include Celluloid::Logger
+
+  # Default broadcast time.
+  # @see #broadcast_time
+  BROADCAST_TIME = 0.020
+
+  # Default election timeout.
+  # @see #election_timeout
+  ELECTION_TIMEOUT = (0.150..0.300)
+
+  # @return [Raft::Log] The replicated log.
+  attr_accessor :log
+
+  # @return [Hash]
+  attr_accessor :options
+
+  # @return [Array<String>] Peers as configured in this cluster.
+  attr_accessor :peers
+
+  # @return [Raft::Node::State::Base] The current state of this node.
+  attr_accessor :state
+
+  # @return [String] id of this node's candidate
+  attr_accessor :voted_for
+
+  # @return [Fixnum] The current term.
+  attr_accessor :term
+
+  # @return [Fixnum] Term of the last log entry.
+  attr_accessor :last_log_term
+
+  # @return [Fixnum] Index of the last log entry.
+  attr_accessor :last_log_index
+
+  # @return [Raft::RPC::Server]
+  attr_accessor :server
+
+  # @return [Raft::RPC::Client]
+  attr_accessor :client
+
+  def initialize(options = {})
+    self.options = options
+    self.term = 0
+    self.last_log_term = 0
+    self.last_log_index = 0
+    self.log = Raft::Log.new
+  end
+
+  def run
+    self.server = link(Raft::RPC::Server.new(options[:listen], &method(:handle_rpc)))
+    self.client = link(Raft::RPC::Client.new)
+    server.run
+    switch_state(:follower)
+  end
+
+  # Execute a command on the replicated state machine.
+  def execute(*args)
+    state.execute(*args)
+  end
+
+  def handle_rpc(command, payload)
+    state.handle_rpc(command, payload)
+  end
+
+  def switch_state(new_state)
+    current_state = state ? state.class.name.split('::').last.downcase : nil
+    info("[TRANSITION] #{current_state} => #{new_state}")
+
+    self.state.exit_state if state
+    self.state = State.const_get(new_state.to_s.capitalize).new(Actor.current)
+    self.state.enter_state
+  end
+
+  # Returns this node's id.
+  # @return [String]
+  def id
+    options[:listen]
+  end
+
+  # Returns peers in the cluster.
+  # @return [Array<String>]
+  def peers
+    options[:peers]
+  end
+
+  # Returns the cluster's quorum.
+  # @return [Fixnum]
+  def cluster_quorum
+    (cluster_size / 2) + 1
+  end
+
+  # Returns the number of nodes in the cluster.
+  # @return [Fixnum]
+  def cluster_size
+    options[:peers].size + 1
+  end
+
+  # The interval between heartbeats (in seconds). See Section 5.7.
+  #
+  # > The broadcast time must be an order of magnitude less than the election timeout so that leaders can reliably send
+  # > the heartbeat messages required to keep followers from starting elections.
+  #
+  # @return [Float]
+  def broadcast_time
+    options[:broadcast_time] || BROADCAST_TIME
+  end
+
+  # Election timeout as defined in Section 5.2.
+  #
+  # This timeout is used in multiple ways:
+  #
+  #   * If a follower does not receive any activity, it starts a new election.
+  #   * As a candidate, if the election does not resolve within this time, it is restarted.
+  #
+  # @return [Range<Float>]
+  def election_timeout
+    options[:election_timeout] || ELECTION_TIMEOUT
+  end
+
+  # A random timeout within {#election_timeout}.
+  # @return [Float]
+  def random_timeout
+    min, max = election_timeout.first, election_timeout.last
+
+    min + rand(max - min)
+  end
+
+  def validate_term(other_term)
+    if other_term < term
+      return false
+    end
+
+    if other_term > term
+      enter_new_term(other_term)
+    end
+
+    true
+  end
+
+  def enter_new_term(new_term = nil)
+    self.term = (new_term || term + 1)
+    self.voted_for = nil
+  end
+
+  %w(info debug warn error).each do |m|
+    define_method(m) do |str|
+      super("[#{id}] #{str}")
+    end
+  end
+end