集群未知网络问题_still have 1 requests outstanding

提交了一个SparkStreaming程序，经常出现如下的错误：

ERROR TransportResponseHandler: Still have 5 requests outstanding when connection from hadoop006/172.33.2.6:55862 is closed
 
WARN YarnSchedulerBackend$YarnSchedulerEndpoint: Attempted to get executor loss reason for executor id 12 at RPC address hadoop008:54388, but got no response. Marking as slave lost.
java.io.IOException: Connection from hadoop006/172.33.2.6:55862 closed
 
ERROR YarnScheduler: Lost executor 12 on hadoop008: Slave lost
 
ERROR TransportClient: Failed to send RPC 8179126089530426088 to hadoop006/172.33.2.6:55862: java.nio.channels.ClosedChannelException
java.nio.channels.ClosedChannelException
 
WARN YarnSchedulerBackend$YarnSchedulerEndpoint: Attempted to get executor loss reason for executor id 2 at RPC address hadoop004:49980, but got no response. Marking as slave lost.
java.io.IOException: Failed to send RPC 8179126089530426088 to hadoop006/172.33.2.6:55862: java.nio.channels.ClosedChannel