Announcing Sawtooth PBFT 1.0

The Sawtooth community is excited to announce the official release of Sawtooth PBFT 1.0 along with the Hyperledger Sawtooth 1.2 release. PBFT 1.0 is the result of substantial engineering effort from Bitwise IO and Cargill to provide a fast and practical consensus algorithm for consortium-style Sawtooth networks.

An earlier blog post, Introduction to Sawtooth PBFT, presented the details of the consensus algorithm. The next post, Sawtooth PBFT, Part 2: Extensions and Changes, described the enhancements that made the algorithm more efficient and easier to implement for Sawtooth. Now, we’d like to describe the advantages of Sawtooth PBFT and give practical tips for how and when to use PBFT consensus.

What Makes PBFT Different?

Those familiar with Sawtooth already know about the Proof of Elapsed Time (PoET) consensus algorithm, a lottery-style (Nakamoto) algorithm that is designed for large, open-enrollment blockchain networks. Until now, PoET was the only production-ready consensus option for Sawtooth. While PoET is useful for certain kinds of networks, it isn’t a universal solution. In particular, PoET is not well suited for smaller networks because of its slower performance.

To make Sawtooth a more versatile blockchain platform, we introduced the dynamic consensus interface in Sawtooth 1.1, which provides a new consensus API that simplifies the process of adding new consensus algorithms. We started with Raft, a simple leader-based consensus algorithm designed for small networks. Raft provided a consensus type that we didn’t have with PoET, but because Raft isn’t Byzantine fault tolerant (BFT), it wasn’t a complete solution.

This is where Sawtooth PBFT comes in. PBFT has properties that make it well suited for small networks — it’s leader-based, non-forking, and fast. It also provides the safety and liveness guarantees that are necessary for operating a blockchain network with adversarial trust. This makes PBFT an excellent option for most consortium-style networks. Consortium networks are small (typically 5-20 nodes), have controlled membership (only administrators can add and remove nodes), and typically require finality (non-forking behavior). Once a block is committed, it is committed forever, which eliminates any uncertainty about the permanence of state.

How Well Does PBFT Work?

Sawtooth PBFT works very well! We’ve tested it extensively for safety, reliability, and performance. The code includes a large number of unit tests that validate PBFT’s functionality, and we’ve run a number of long-running PBFT networks to work out the kinks.

How does PBFT Perform?

Part of the extensive testing of PBFT was determining how well it performs. A full Sawtooth network consisting of 10 “m5.large” AWS instances running with PBFT consensus performed 2.5x faster than the same network running with PoET consensus.

Exact results may vary depending on factors like system resources and network size, but the big picture is pretty clear: PBFT can provide a big performance boost compared to PoET.

When Should I Use PBFT?

The short answer is that PBFT should be considered the first choice for small to medium Sawtooth networks that do not require open enrollment. If your use case requires a large network (more than 20 nodes, for instance) or open enrollment, PoET may be a better choice because it is designed to perform well with many nodes and is less strict about membership in the network. But, in general, we recommend using PBFT because of its finality and performance advantages for most networks.

How Do I Use PBFT?

Sawtooth PBFT is easy to configure and use. We designed Sawtooth’s dynamic consensus interface to make choosing consensus simple. The Sawtooth 1.2 documentation includes instructions for setting up a Sawtooth network with PBFT using Docker and Kubernetes, which are designed for application development environments and Proof of Concept evaluations. For production networks and do-it-yourself developers, there’s also a procedure for setting up a Sawtooth network on Ubuntu.

See For Yourself

Sawtooth PBFT is an exciting new addition to the Hyperledger Sawtooth ecosystem. If you’d like to learn more:

About the Author

Logan Seeley is a Software Engineer at Bitwise IO. He has been a part of the Hyperledger Sawtooth community since May 2018, working in a variety of areas including consensus, Hyperledger Sawtooth, and Hyperledger Transact.

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