Technical Technical — Cassandra Friday 14th February 2020

Apache Cassandra 4.0 – Netty Transport

By Ben Bromhead

In this series of blog posts, we’ll take a meandering tour of some of the important changes, cool features, and nice ergonomics that are coming with Apache Cassandra 4.0. In part 1 we focussed on Cassandra 4.0 stability and testing, and Part 2 around virtual tables. In this part we will learn about Netty Transport Framework

One of the headline features for Apache Cassandra 4.0 is the refactor of internode messaging to use Javas (non-blocking) NIO capability ( and via the Netty library (link to Netty). 

This allows Cassandra to move away from having an N threads per peer model, to a single thread pool for all connections. This dramatically reduces performance issues related to thread signalling, coordination and context switching.

Moving to the Netty framework has also enabled other features like zero copy streaming for SSTables.

Performance improvements have been apparent from day one, both in terms of throughput and latency. The big win however is the significant reduction in tail end latency with up to 40%+ reductions in P99s seen in initial testing.  

Of course patches and improvements are being made all the time during the beta process, so benchmarking will need to be revalidated against each workload and within your own environment, but progress is promising!