Caught exception while handling client http traffic, closing connection

[V15HAL]

I was Indexing into my Elastic Cluster (with 2 nodes) & I got the following Error Message.
Other Info:
Bulk Size = 5000
Indexing Rate was= 5000 to 6500 documents per second
I was using a Transport Client.
The Indexing program stopped with the following error log of Elastic.

Can you please suggest what can be the possible cause for this error and how to resolve/avoid this in future.?

[es-01] Caught exception while handling client http traffic, closing connection [id: 0xc83845d2, /172.19.33.101:59676 => /172.23.12.91:9200]
java.io.IOException: No route to host
        at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
        at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39)
        at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
        at sun.nio.ch.IOUtil.read(IOUtil.java:192)
        at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:379)
        at org.elasticsearch.common.netty.channel.socket.nio.NioWorker.read(NioWorker.java:64)
        at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioWorker.process(AbstractNioWorker.java:108)
        at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:337)
        at org.elasticsearch.common.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
        at org.elasticsearch.common.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
        at org.elasticsearch.common.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
        at org.elasticsearch.common.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)