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README.md

Sawtooth PBFT

This repository contains an implementation of the Practical Byzantine Fault Tolerant (PBFT) consensus algorithm for Hyperledger Sawtooth.

Status

This project is in a highly experimental stage - there is a significant amount of work to be done before it is ready to be deployed in a production context. Please beware that this repository may change often.

The proposal for its inclusion in Sawtooth is located in the associated RFC.

About PBFT

PBFT (Practical Byzantine Fault Tolerance) is a Byzantine fault-tolerant consensus algorithm that was pioneered by Miguel Castro and Barbara Liskov in 1999. PBFT is designed to tolerate nodes in a distributed network failing, and sending incorrect messages to other nodes, as long as fewer than one-third of the nodes are considered faulty. PBFT networks need a minimum of four nodes to be Byzantine fault-tolerant.

This implementation is based around the algorithm described in that paper, and adapted for use in Hyperledger Sawtooth. It uses the experimental Consensus API that is loosely described by this RFC.

Note that this project uses the terms "primary" and "secondary" to refer to the role of nodes in the network, which differs slightly from the terminology used in the PBFT paper. "Primary" is synonymous with "leader," and "secondary" is synonymous with "follower," and "backup." "Node" is synonymous with "server" and "replica."

Motivation

Sawtooth currently only supports PoET consensus (although other algorithms like Raft are currently under development). PoET is only crash fault tolerant, so if any nodes in the network exhibit Byzantine behaviour, it causes issues with consensus.

Features

The following features have been implemented:

  • Normal case operation: Handling transactions when the network is functioning normally
  • View changes: When a primary node is considered faulty (crashed or malicious), the network changes views and a new primary is elected.
  • Log garbage collection: Every so often, message logs should be garbage collected so as to not take up too much space.
  • Testing improvements: Presently, a liveness test up to 55 blocks has been performed on a network of four nodes. Unit tests are also included for each individual component of the algorithm.

The following features are desired (not a comprehensive list):

  • Allow network changes: Right now, the network is assumed to be static. Peers are introduced through on-chain settings, and the peer list does not change during network operation.
  • Persistent storage: Nodes should be able to recover from crashes by saving their logs in persistent storage instead of keeping everything in memory
  • Documentation: Use existing Sawtooth doc generation to create documentation for this project

Running PBFT

  • Clone this repo: git clone https://github.com/bridger-herman/sawtooth-pbft.git and checkout the branch you're interested in (probably unit-tests)
  • Run the following commands:

Use the following steps to start a four-node network and run a liveness test:

  1. Clone the PBFT repo: git clone https://github.com/bitwiseio/sawtooth-pbft.git

  2. Run the following commands to connect to the sawtooth-dev-pbft interactive shell:

    cd sawtooth-pbft
    
    docker build . -f Dockerfile -t sawtooth-dev-pbft
    
    docker run -v $(pwd):/project/sawtooth-pbft -it sawtooth-dev-pbft bash
    
    # You can optionally use this to speed up your build times, if you have a cargo-registry Docker volume set up:
    docker run -v $(pwd):/project/sawtooth-pbft -v cargo-registry:/root/.cargo/registry -it sawtooth-dev-pbft bash
    
  3. Once you have the sawtooth-dev-pbft interactive shell up, run:

    cargo build
    
  4. Once the project finishes building, exit the interactive shell and run

    tests/pbft.sh
    

This script first builds a few docker images, then starts up a network of four nodes and goes through a liveness test of 55 blocks (using the Docker Compose file test_liveness.yaml). The default log level is INFO, so it prints out quite a bit of information as the algorithm executes. All of the on-chain settings (such as block duration and view change timeout) can be adjusted inside of the file tests/test_liveness.yaml, as well as the log level for each of the services in the network.

If you'd like to specify a different Docker Compose file to use (such as grafana.yaml, client.yaml, or pbft_unit_tests.yaml), provide pbft.sh with an additional argument:

tests/pbft.sh pbft_unit_tests

If you'd like to pass additional arguments to Docker Compose, they go after the compose file you're using:

tests/pbft.sh client --abort-on-container-exit