How to fix the “Found Netty's native epoll transport in the classpath, but epoll is not available. Using NIO instead” warning?

Question

I am using Cassandra and, during startup, Netty prints a warning with a stack trace:

Found Netty\'s native epoll transport in the classpath, but epoll

Answer 1

If you are running on Linux, you can use the native Linux driver. For instance, if you are using Maven, add a dependency like this:

<dependency>
  <groupId>io.netty</groupId>
  <artifactId>netty-transport-native-epoll</artifactId>
  <version>4.0.27.Final</version>
  <classifier>linux-x86_64</classifier>
</dependency>

An alternative, you can suppress the warning by setting -Dcom.datastax.driver.FORCE_NIO=true. As it is only a performance optimization, it is a viable option to ignore it.

For more background, refer to the Netty documentation about native transports.