Class: ZK::Election::Base

Inherits:
Object
  • Object
show all
Includes:
Logger
Defined in:
lib/zk/election.rb

Direct Known Subclasses

Candidate, Observer

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Logger

#logger, wrapped_logger, wrapped_logger=

Constructor Details

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

Returns a new instance of Base.


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# File 'lib/zk/election.rb', line 67

def initialize(client, name, opts={})
  @zk = client
  @name = name
  opts = DEFAULT_OPTS.merge(opts)
  @root_election_node = opts[:root_election_node]
  @mutex = Monitor.new
  @closed = false
end

Instance Attribute Details

#root_election_nodeObject (readonly)

Returns the value of attribute root_election_node.


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# File 'lib/zk/election.rb', line 65

def root_election_node
  @root_election_node
end

#vote_pathObject (readonly)

Returns the value of attribute vote_path.


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# File 'lib/zk/election.rb', line 65

def vote_path
  @vote_path
end

#zkObject (readonly)

Returns the value of attribute zk.


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# File 'lib/zk/election.rb', line 65

def zk
  @zk
end

Instance Method Details

#cast_ballot!(data) ⇒ Object


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# File 'lib/zk/election.rb', line 95

def cast_ballot!(data)
  return if @vote_path
  create_root_path!
  @vote_path = @zk.create("#{root_vote_path}/#{VOTE_PREFIX}", data, :mode => :ephemeral_sequential)
rescue Exceptions::NoNode
  retry
end

#closeObject


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# File 'lib/zk/election.rb', line 76

def close
  @mutex.synchronize do
    return if @closed
    @closed = true
  end
end

#leader_ack_pathObject

this znode will be created as an acknowledgement by the leader that it's aware of its status as the new leader and has run its procedures to become master


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# File 'lib/zk/election.rb', line 91

def leader_ack_path
  @leader_ack_path ||= "#{root_vote_path}/leader_ack"
end

#leader_acked?(watch = false) ⇒ Boolean

has the leader acknowledged their role?

Returns:

  • (Boolean)

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# File 'lib/zk/election.rb', line 104

def leader_acked?(watch=false)
  @zk.exists?(leader_ack_path, :watch => watch)
end

#leader_dataObject

return the data from the current leader or nil if there is no current leader


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# File 'lib/zk/election.rb', line 109

def leader_data
  @zk.get(leader_ack_path).first
rescue Exceptions::NoNode
end

#on_leader_ack(&block) ⇒ Object

Asynchronously call the block when the leader has acknowledged its role.


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# File 'lib/zk/election.rb', line 116

def on_leader_ack(&block)
  creation_sub = @zk.register(leader_ack_path, :only => [:created, :changed]) do |event|
    return if @closed
    begin
      logger.debug { "in #{leader_ack_path} watcher, got creation event, notifying" }
      safe_call(block)
    ensure
      creation_sub.unregister
    end
  end

  deletion_sub = @zk.register(leader_ack_path, :only => [:deleted, :child]) do |event|
    if @zk.exists?(leader_ack_path, :watch => true)
      return if @closed
      begin
        logger.debug { "in #{leader_ack_path} watcher, node created behind our back, notifying" }
        safe_call(block)
      ensure
        creation_sub.unregister
      end
    else
      logger.debug { "in #{leader_ack_path} watcher, got non-creation event, re-watching" }
    end
  end

  subs = [creation_sub, deletion_sub]

  if @zk.exists?(leader_ack_path, :watch => true)
    logger.debug { "on_leader_ack, #{leader_ack_path} exists, calling block" }
    begin
      safe_call(block)
    ensure
      subs.each { |s| s.unregister }
    end
  end
end

#root_vote_pathObject

holds the ephemeral nodes of this election


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# File 'lib/zk/election.rb', line 84

def root_vote_path #:nodoc:
  @root_vote_path ||= "#{@root_election_node}/#{@name.gsub('/', '__')}"
end