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

Returns a new instance of Node.



186
187
188
189
190
191
192
193
194
195
 
# File 'lib/raft.rb', line 186

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, config.election_splay)
  @commit_handler = commit_handler || (block.to_proc if block_given?)
end

Instance Attribute Details

#cluster ⇒ Object (readonly)

Returns the value of attribute cluster.



177
178
179
 
# File 'lib/raft.rb', line 177

def cluster
  @cluster
end

#config ⇒ Object (readonly)

Returns the value of attribute config.



176
177
178
 
# File 'lib/raft.rb', line 176

def config
  @config
end

#election_timer ⇒ Object (readonly)

Returns the value of attribute election_timer.



180
181
182
 
# File 'lib/raft.rb', line 180

def election_timer
  @election_timer
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



174
175
176
 
# File 'lib/raft.rb', line 174

def id
  @id
end

#persistent_state ⇒ Object (readonly)

Returns the value of attribute persistent_state.



178
179
180
 
# File 'lib/raft.rb', line 178

def persistent_state
  @persistent_state
end

#role ⇒ Object (readonly)

Returns the value of attribute role.



175
176
177
 
# File 'lib/raft.rb', line 175

def role
  @role
end

#temporary_state ⇒ Object (readonly)

Returns the value of attribute temporary_state.



179
180
181
 
# File 'lib/raft.rb', line 179

def temporary_state
  @temporary_state
end

Instance Method Details

#handle_append_entries(request) ⇒ Object 



409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
 
# File 'lib/raft.rb', line 409

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

  #STDOUT.write("\n\nnode #{@id} handle_append_entries for term #{request.term} (current is #{@persistent_state.current_term})\n")# if request.prev_log_index.nil?
  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 



443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
 
# File 'lib/raft.rb', line 443

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 



373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
 
# File 'lib/raft.rb', line 373

def handle_request_vote(request)
  #STDOUT.write("\nnode #{@id} handling vote request from #{request.candidate_id} (request.last_log_index: #{request.last_log_index}, vs #{@persistent_state.log.last.index}\n")
  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 || -1) < @persistent_state.log.last.index
        # candidate's log is incomplete compared to this node
      elsif (request.last_log_term || -1) < @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 



197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
 
# File 'lib/raft.rb', line 197

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