Class: ZK::Election::Candidate

Inherits:

Base

• Object
• Base
• ZK::Election::Candidate

Defined in:

lib/zk/election.rb

Overview

This class is for registering candidates in the leader election. This instance will participate in votes for becoming the leader and will be notified in the case where it needs to take over.

if data is given, it will be used as the content of both our ballot and the leader acknowledgement node if and when we become the leader.

Instance Attribute Summary

Attributes inherited from Base

#root_election_node, #vote_path, #zk

Instance Method Summary

• #initialize(client, name, opts = {}) ⇒ Candidate constructor

  A new instance of Candidate.

• #leader? ⇒ Boolean
• #on_losing_election(&block) ⇒ Object

  When we lose the election and are relegated to the shadows, waiting for the leader to make one small misstep, where we can finally claim what is rightfully ours! MWUAHAHAHAHAHA(cough).

• #on_takeover_error ⇒ Object

  These procs should be run in the case of an error when trying to assume the leadership role.

• #on_winning_election(&block) ⇒ Object

  When we win the election, we will call the procs registered using this method.

• #vote! ⇒ Object

  volunteer to become the leader.

• #voted? ⇒ Boolean

  true if leader has been determined at least once (used in tests).

Methods inherited from Base

#cast_ballot!, #close, #leader_ack_path, #leader_acked?, #leader_data, #on_leader_ack, #root_vote_path

Methods included from Logger

#logger, wrapped_logger, wrapped_logger=

Constructor Details

#initialize(client, name, opts = {}) ⇒ Candidate

Returns a new instance of Candidate.

# File 'lib/zk/election.rb', line 191

def initialize(client, name, opts={})
  super(client, name, opts)
  opts = DEFAULT_OPTS.merge(opts)

  @leader     = nil 
  @data       = opts[:data] || ''
  @vote_path  = nil
 
  @winner_callbacks = []
  @loser_callbacks = []

  @next_node_ballot_sub = nil # the subscription for next-node failure
end

Instance Method Details

#leader? ⇒ Boolean

Returns:

• (Boolean)

# File 'lib/zk/election.rb', line 205

def leader?
  false|@leader
end

#on_losing_election(&block) ⇒ Object

When we lose the election and are relegated to the shadows, waiting for the leader to make one small misstep, where we can finally claim what is rightfully ours! MWUAHAHAHAHAHA(cough)

# File 'lib/zk/election.rb', line 223

def on_losing_election(&block)
  @loser_callbacks << block
end

#on_takeover_error ⇒ Object

These procs should be run in the case of an error when trying to assume the leadership role. This should probably be a "hara-kiri" or STONITH type procedure (i.e. kill the candidate)

Raises:

• (NotImplementedError)

# File 'lib/zk/election.rb', line 231

def on_takeover_error #:nodoc:
  raise NotImplementedError
end

#on_winning_election(&block) ⇒ Object

When we win the election, we will call the procs registered using this method.

# File 'lib/zk/election.rb', line 216

def on_winning_election(&block)
  @winner_callbacks << block
end

#vote! ⇒ Object

volunteer to become the leader. if we win, on_winning_election blocks will be called, otherwise, wait for next election

+data+ will be placed in the znode representing our vote

# File 'lib/zk/election.rb', line 239

def vote!
  synchronize do
    clear_next_node_ballot_sub!
    cast_ballot!(@data) unless @vote_path
    check_election_results!
  end
end

#voted? ⇒ Boolean

true if leader has been determined at least once (used in tests)

Returns:

• (Boolean)

# File 'lib/zk/election.rb', line 210

def voted? #:nodoc:
  !@leader.nil?
end