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libhotstuff
-----------
libhotstuff is a general-purpose BFT state machine replication library with
modularity and simplicity, suitable for building hybrid consensus
cryptocurrencies.
Paper
=====
This repo includes the prototype implementation evaluated in our *HotStuff: BFT
Consensus in the Lens of Blockchain* paper. The consensus protocol is also used
by Facebook in Libra_ project.
Feel free to contact us if you'd like to reproduce the results in the paper, or
tweak the code for your own project/product.
- Full paper: https://arxiv.org/abs/1803.05069
- PODC 2019 paper: https://dl.acm.org/citation.cfm?id=3331591
.. _Libra: https://github.com/libra
Features
========
- Simplicity. The protocol core logic implementation is as simple as the one
specified in our paper. See ``consensus.h`` and ``consensus.cpp``.
- Modular design. You can use abstraction from the lowest level (the core
protocol logic) to the highest level (the state machine replication service
with network implementation) in your application, or override/redefine the
detailed behavior to customize your own consensus.
- Liveness decoupled from safety. The liveness logic is entirely decoupled from
safety. By defining your own liveness gadget ("PaceMaker"), you can implement
your own liveness heuristics/algorithm. The actual performance varies
depending on your liveness implementation, but the safety is always intact.
- Friendly to blockchain systems. A PaceMaker could potentially be PoW-based and
it makes it easier to build a hybrid consensus system, or use it at the core of
some cryptocurrencies.
- Minimal. The project strives to keep code base small and implement just the
basic functionality of state machine replication: to deliver a consistent
command sequence to the library user. Application-specific parts are not
included, but demonstrated in the demo program.
Try the Current Version
=======================
NOTICE: the project is still in-progress. Try at your own risk, and this
section may be incomplete and subject to changes.
::
# install from the repo
git clone https://github.com/hot-stuff/libhotstuff.git
cd libhotstuff/
git submodule update --init --recursive
# ensure openssl and libevent are installed on your machine, more
# specifically, you need:
#
# CMake >= 3.9 (cmake)
# C++14 (g++)
# libuv >= 1.10.0 (libuv1-dev)
# openssl >= 1.1.0 (libssl-dev)
#
# on Ubuntu: sudo apt-get install libssl-dev libuv1-dev cmake make
cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED=ON -DHOTSTUFF_PROTO_LOG=ON
make
# start 4 demo replicas with scripts/run_demo.sh
# then, start the demo client with scripts/run_demo_client.sh
# Fault tolerance:
# Try to run the replicas as in run_demo.sh first and then run_demo_client.sh.
# Use Ctrl-C to terminate the proposing replica (e.g. replica 0). Leader
# rotation will be scheduled. Try to kill and run run_demo_client.sh again, new
# commands should still get through (be replicated) once the new leader becomes
# stable. Or try the following script:
# scripts/faulty_leader_demo.sh
Try to Reproduce Our Basic Results
==================================
See here_.
TODO (When I get some free time...)
===================================
- Rewrite this minimal code base in Rust: this time, with all the experience,
without C++ template kung-fu, I plan to have a ready-to-use, blackbox-like
libhotstuff implementation as a full library with better encapsulation and
interface. The new goal would be *any* engineer without knowledge of BFT
should be able to use it for his/her own application, without changing the
library code. Ping me if you like this re-writing idea or you'd like to
be part of it.
- Limit the async event callback depth (otherwise in the demo a fresh replica
could overflow its callback stack when trying to catch up)
- Add a PoW-based Pacemaker example
- Branch pruning & swapping (the current implementation stores the entire chain in memory)
- Persistent protocol state (recovery?)
.. _here: https://github.com/hot-stuff/libhotstuff/tree/master/scripts/deploy
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