Worker hangs when the external shuffle service port is already in use

17/09/29 11:16:30 INFO ExternalShuffleService: Starting shuffle service on port 7337 (auth enabled = false)
17/09/29 11:16:30 ERROR Inbox: Ignoring error
java.net.BindException: Address already in use
        at sun.nio.ch.Net.bind0(Native Method)
        at sun.nio.ch.Net.bind(Net.java:433)
        at sun.nio.ch.Net.bind(Net.java:425)
        at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
        at io.netty.channel.socket.nio.NioServerSocketChannel.doBind(NioServerSocketChannel.java:128)
        at io.netty.channel.AbstractChannel$AbstractUnsafe.bind(AbstractChannel.java:500)
        at io.netty.channel.DefaultChannelPipeline$HeadContext.bind(DefaultChannelPipeline.java:1218)
        at io.netty.channel.AbstractChannelHandlerContext.invokeBind(AbstractChannelHandlerContext.java:495)
        at io.netty.channel.AbstractChannelHandlerContext.bind(AbstractChannelHandlerContext.java:480)
        at io.netty.channel.DefaultChannelPipeline.bind(DefaultChannelPipeline.java:965)
        at io.netty.channel.AbstractChannel.bind(AbstractChannel.java:209)
        at io.netty.bootstrap.AbstractBootstrap$2.run(AbstractBootstrap.java:355)
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:399)