I'm using apache cassandra 2.2.4. I have a 4 (four) node cluster with Replication Factor 3 in DC1 and Replication Factor 1 in DC2, where DC1 contains 3 (three) nodes and DC2 contains 1 (one) node. There were some more nodes before in this cluster, but for some reason I removed them and didn't altered the replication scenario. [Please consider that the following IP's are not original]
Datacenter: DC1
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 21.12.19.91 4.08 GB 256 ? a45bb676-1ddd-4b22-933b-58653cea680f RAC1
UN 21.12.19.92 3.92 GB 256 ? a7735fca-8671-4a20-a759-4a2681aed37e RAC1
UN 21.12.19.93 4.47 GB 256 ? d98f3cad-881a-41c8-89c7-170c63c3d236 RAC1
Datacenter: DC2
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 21.12.19.99 3.84 GB 256 ? ccd9ca97-f97a-4473-9a65-49b12a1b60ba RAC1
Cluster was working fine, but now-a-days I'm having an issue as INFO. I was trying to analyze the issue, but couldn't make it yet. Is there anyone, who is familiar with following scenario?
INFO [SharedPool-Worker-2] 2017-02-26 06:56:48,520 Message.java:605 - Unexpected exception during request; channel = [id: 0x637a702c, /18.12.10.17:60926 :> /21.12.19.91:9042]
java.io.IOException: Error while read(...): Connection reset by peer
at io.netty.channel.epoll.Native.readAddress(Native Method) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.epoll.EpollSocketChannel$EpollSocketUnsafe.doReadBytes(EpollSocketChannel.java:675) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.epoll.EpollSocketChannel$EpollSocketUnsafe.epollInReady(EpollSocketChannel.java:714) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:326) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:264) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_66]
Please make sure that your Firewall is not dropping TCP connections which are in use. Tcp keep alive on all nodes must be less than the firewall setting. Please refer to https://docs.datastax.com/en/cassandra/2.0/cassandra/troubleshooting/trblshootIdleFirewall.html for details on TCP settings. This helped me resolve the issue.
来源：https://stackoverflow.com/questions/42477913/unexpected-exception-during-request