zookeeper选举-Messenger

FastLeaderElection.Messenger 
投票信息传输

protected class Messenger {

        WorkerSender ws;

        WorkerReceiver wr;

        Messenger(QuorumCnxManager manager) {
            this.ws = new WorkerSender(manager);
            Thread t = new Thread(this.ws, "WorkerSender[myid=" + self.getId() + "]");
            t.setDaemon(true);
            t.start();

            this.wr = new WorkerReceiver(manager);
            t = new Thread(this.wr, "WorkerReceiver[myid=" + self.getId() + "]");
            t.setDaemon(true);
            t.start();
        }

        void halt() {
            this.ws.stop = true;
            this.wr.stop = true;
        }
    }