elasticsearch从5.1.1 升级到5.6.5 在同步副本数据时报错

[2017-12-18T14:09:17,711][WARN ][o.e.t.n.Netty4Transport  ] [elastic-node2] write and flush on the network layer failed (channel: [id: 0x46368407, L:0.0.0.0/0.0.0.0:9300 ! R:/172.19.7.133:15852])
java.nio.channels.ClosedChannelException: null
at io.netty.channel.AbstractChannel$AbstractUnsafe.write(...)(Unknown Source) ~[?:?]
[2017-12-18T14:11:49,732][WARN ][o.e.t.n.Netty4Transport  ] [elastic-node2] write and flush on the network layer failed (channel: [id: 0xb6455ba0, L:0.0.0.0/0.0.0.0:9300 ! R:/172.19.7.133:16068])
java.nio.channels.ClosedChannelException: null
at io.netty.channel.AbstractChannel$AbstractUnsafe.write(...)(Unknown Source) ~[?:?]