Class: Raft::Node

Inherits:
Object
  • Object
show all
Defined in:
lib/raft.rb

Constant Summary collapse

FOLLOWER_ROLE = 
0
CANDIDATE_ROLE = 
1
LEADER_ROLE = 
2

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(id, config, cluster, commit_handler = nil, &block) ⇒ Node 



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# File 'lib/raft.rb', line 163

def initialize(id, config, cluster, commit_handler=nil, &block)
  @id = id
  @role = FOLLOWER_ROLE
  @config = config
  @cluster = cluster
  @persistent_state = PersistentState.new
  @temporary_state = TemporaryState.new(nil, nil)
  @election_timer = Timer.new(config.election_timeout)
  @commit_handler = commit_handler || (block.to_proc if block_given?)
end

Instance Attribute Details

#cluster ⇒ Object (readonly)

Returns the value of attribute cluster.



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# File 'lib/raft.rb', line 154

def cluster
  @cluster
end

#config ⇒ Object (readonly)

Returns the value of attribute config.



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# File 'lib/raft.rb', line 153

def config
  @config
end

#election_timer ⇒ Object (readonly)

Returns the value of attribute election_timer.



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# File 'lib/raft.rb', line 157

def election_timer
  @election_timer
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



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# File 'lib/raft.rb', line 151

def id
  @id
end

#persistent_state ⇒ Object (readonly)

Returns the value of attribute persistent_state.



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# File 'lib/raft.rb', line 155

def persistent_state
  @persistent_state
end

#role ⇒ Object (readonly)

Returns the value of attribute role.



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# File 'lib/raft.rb', line 152

def role
  @role
end

#temporary_state ⇒ Object (readonly)

Returns the value of attribute temporary_state.



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# File 'lib/raft.rb', line 156

def temporary_state
  @temporary_state
end

Instance Method Details

#handle_append_entries(request) ⇒ Object 



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# File 'lib/raft.rb', line 383

def handle_append_entries(request)
  #STDOUT.write("\n\nnode #{@id} handle_append_entries: #{request.entries.pretty_inspect}\n\n") if request.prev_log_index.nil?
  response = AppendEntriesResponse.new
  response.term = @persistent_state.current_term
  response.success = false

  return response if request.term < @persistent_state.current_term
  #STDOUT.write("\n\nnode #{@id} handle_append_entries stage 2\n") if request.prev_log_index.nil?

  step_down_if_new_term(request.term)

  reset_election_timeout

  @temporary_state.leader_id = request.leader_id

  abs_log_index = abs_log_index_for(request.prev_log_index, request.prev_log_term)
  return response if abs_log_index.nil? && !request.prev_log_index.nil? && !request.prev_log_term.nil?
  #STDOUT.write("\n\nnode #{@id} handle_append_entries stage 3\n") if request.prev_log_index.nil?
  if @temporary_state.commit_index &&
      abs_log_index &&
      abs_log_index < @temporary_state.commit_index
    raise "Cannot truncate committed logs; @temporary_state.commit_index = #{@temporary_state.commit_index}; abs_log_index = #{abs_log_index}"
  end

  truncate_and_update_log(abs_log_index, request.entries)

  return response unless update_commit_index(request.commit_index)
  #STDOUT.write("\n\nnode #{@id} handle_append_entries stage 4\n") if request.prev_log_index.nil?

  response.success = true
  response
end

#handle_command(request) ⇒ Object 



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# File 'lib/raft.rb', line 416

def handle_command(request)
  response = CommandResponse.new(false)
  case @role
  when FOLLOWER_ROLE
    await_leader
    if @role == LEADER_ROLE
      handle_command(request)
    else
      # forward the command to the leader
      response = @config.rpc_provider.command(request, @temporary_state.leader_id)
    end
  when CANDIDATE_ROLE
    await_leader
    response = handle_command(request)
  when LEADER_ROLE
    last_log = @persistent_state.log.last
    log_entry = LogEntry.new(@persistent_state.current_term, last_log.index ? last_log.index + 1 : 0, request.command)
    @persistent_state.log << log_entry
    await_consensus(log_entry)
    response = CommandResponse.new(true)
  end
  response
end

#handle_request_vote(request) ⇒ Object 



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# File 'lib/raft.rb', line 348

def handle_request_vote(request)
  response = RequestVoteResponse.new
  response.term = @persistent_state.current_term
  response.vote_granted = false

  return response if request.term < @persistent_state.current_term

  @temporary_state.leader_id = nil if request.term > @persistent_state.current_term

  step_down_if_new_term(request.term)

  if FOLLOWER_ROLE == @role
    if @persistent_state.voted_for == request.candidate_id
      response.vote_granted = success
    elsif @persistent_state.voted_for.nil?
      if @persistent_state.log.empty?
        # this node has no log so it can't be ahead
        @persistent_state.voted_for = request.candidate_id
        response.vote_granted = true
      elsif request.last_log_term == @persistent_state.log.last.term &&
          request.last_log_index && request.last_log_index < @persistent_state.log.last.index
        # candidate's log is incomplete compared to this node
      elsif request.last_log_term && request.last_log_term < @persistent_state.log.last.term
        # candidate's log is incomplete compared to this node
      else
        @persistent_state.voted_for = request.candidate_id
        response.vote_granted = true
      end
    end
    reset_election_timeout if response.vote_granted
  end

  response
end

#update ⇒ Object 



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# File 'lib/raft.rb', line 174

def update
  return if @updating
  @updating = true
  indent = "\t" * (@id.to_i % 3)
  #STDOUT.write("\n\n#{indent}update #{@id}, role #{@role}, log length #{@persistent_state.log.count}\n\n")
  case @role
  when FOLLOWER_ROLE
    follower_update
  when CANDIDATE_ROLE
    candidate_update
  when LEADER_ROLE
    leader_update
  end
  @updating = false
end