A complete implementation of the Raft Consensus Algorithm as a C library, licensed under BSD.

This is a fork of the original library created by Willem-Hendrik Thiart, which is now actively maintained by Redis Ltd. and used as part of RedisRaft.

See raft.h for full API documentation.

Main Features

The library implements all basic features of Raft as well as some extensions, including:

• Leader election
• Log replication and FSM interface
• Compaction and snapshot support
• Cluster membership changes
• Quorum check and step-down by leader
• Pre-vote
• Leadership transfer

The library is completely abstract and it is up to the caller to implement things like:

• RPC and networking
• Log storage and access
• Generation of snapshots from FSM state

Getting Started

To build and run basic tests:

make tests

If you prefer, you can also use cmake:

mkdir build
cd build
cmake ..
make
make test

Tests

The library uses the following testing methods:

• A simulator (virtraft2) is used to test the Raft invariants on unreliable networks
• All bugs have regression tests
• Many unit tests

virtraft2

This cluster simulator checks the following:

• Log Matching (servers must have matching logs)
• State Machine Safety (applied entries have the same ID)
• Election Safety (only one valid leader per term)
• Current Index Validity (does the current index have an existing entry?)
• Entry ID Monotonicity (entries aren't appended out of order)
• Committed entry popping (committed entries are not popped from the log)
• Log Accuracy (does the server's log match mirror an independent log?)
• Deadlock detection (does the cluster continuously make progress?)

Chaos generated by virtraft2:

• Random bi-directional partitions between nodes
• Message dropping
• Message duplication
• Membership change injection
• Random compactions

Run the simulator using:

mkdir .env
virtualenv .env
source .env/bin/activate
pip install -r tests/requirements.txt
make test_virtraft

Requirements

• Python 3.9 or later