@Override
	public synchronized void start() {
		if (zkServerThread == null) {
			zkServerThread = new Thread(new ServerRunnable(), "ZooKeeper Server Starter");
			zkServerThread.setDaemon(true);
			zkServerThread.start();
		}
	}
Start the ZooKeeper server in a background thread.
<p>
Register an error handler via {@link #setErrorHandler} in order to handle
any exceptions thrown during startup or execution.
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/zookeeper/EmbeddedZooKeeper.java