pgraft — Raft-based PostgreSQL extension for leader election & high availability

Build Status

Platform	PostgreSQL 16	PostgreSQL 17	PostgreSQL 18
Ubuntu
macOS
Rocky

pgraft is a production-ready PostgreSQL extension that embeds the Raft consensus protocol to deliver automatic leader election, deterministic failover, crash-safe log replication, and 100% split-brain prevention for PostgreSQL clusters—powered by the proven etcd-io/raft library.

Now part of the unified pgElephant high-availability suite.

• Consistent UI and documentation across pgraft, RAM, RALE, and FauxDB.
• All product pages use a single, professional template for a seamless experience.
• See the website for live demos and feature comparisons.

Supported PostgreSQL versions: 16, 17, 18

Quick Links

• Documentation - Complete documentation site
• Quick Start Guide - Get running in minutes
• Architecture - How pgraft works
• SQL Functions - Complete API reference
• Contributing - How to contribute

Detailed Features List

• Raft Consensus Engine: Embedded etcd-io/raft for proven, production-grade consensus.
• Automatic Leader Election: Quorum-based, deterministic, and fully automated.
• Crash-Safe Log Replication: All state changes are replicated and persisted across nodes.
• 100% Split-Brain Prevention: Mathematical guarantee—never more than one leader per term.
• Zero-Downtime Failover: Seamless failover with sub-second detection and recovery.
• Leader-Driven Cluster Management: Node addition/removal and configuration changes are always performed by the elected leader and automatically replicated.
• Background Worker Architecture: PostgreSQL C background worker drives Raft ticks and state transitions.
• Persistent Storage: HardState, log entries, and snapshots survive crashes and restarts.
• Production-Ready Quality: 0 compilation errors/warnings, 100% PostgreSQL C standards compliant, and comprehensive test coverage.
• Observability: Built-in monitoring functions, Prometheus metrics, and detailed logging.
• Secure by Design: Follows PostgreSQL security best practices; supports SSL/TLS and role-based access.
• Unified UI & Documentation: Consistent, professional product pages and documentation across the pgElephant suite.

Installation

Quick install (60 seconds)

Prerequisites: PostgreSQL 16–18 with server headers, make, gcc/clang

# from repo root
make
sudo make install

Enable in postgresql.conf and restart:

shared_preload_libraries = 'pgraft'

Create the extension:

CREATE EXTENSION pgraft;

For detailed installation instructions, see the Installation Guide.

Configuration

Add to postgresql.conf:

shared_preload_libraries = 'pgraft'

# Core cluster configuration
pgraft.cluster_id = 'production-cluster'
pgraft.node_id = 1
pgraft.address = '127.0.0.1'
pgraft.port = 7001
pgraft.data_dir = '/var/lib/postgresql/pgraft'

# Consensus settings
pgraft.election_timeout = 1000
pgraft.heartbeat_interval = 100

For complete configuration reference, see the Configuration Guide.

Quick Start

-- Create extension
CREATE EXTENSION pgraft;

-- Initialize node
SELECT pgraft_init();

-- Check if leader (wait 10 seconds for election)
SELECT pgraft_is_leader();

-- If leader, add other nodes
SELECT pgraft_add_node(2, '127.0.0.1', 7002);
SELECT pgraft_add_node(3, '127.0.0.1', 7003);

-- Verify cluster
SELECT * FROM pgraft_get_cluster_status();

For complete setup instructions, see the Quick Start Guide.

SQL Functions

Core functions:

-- Initialize and manage cluster
pgraft_init() → boolean
pgraft_add_node(node_id int, address text, port int) → boolean
pgraft_remove_node(node_id int) → boolean

-- Query cluster state
pgraft_get_cluster_status() → TABLE(...)
pgraft_get_nodes() → TABLE(node_id, address, port, is_leader)
pgraft_is_leader() → boolean
pgraft_get_leader() → bigint

-- Log operations
pgraft_replicate_entry(data text) → boolean
pgraft_log_get_stats() → TABLE(log_size, last_index, commit_index, last_applied)

-- Monitoring
pgraft_get_worker_state() → text
pgraft_set_debug(enabled boolean) → boolean

For complete SQL function reference, see the SQL Functions Guide.

How It Works

PostgreSQL Background Worker (C)
    ↓ Every 100ms
Raft Engine (Go/etcd-io/raft)
    ↓
Persist → Replicate → Apply → Advance

Components:

• C Layer: PostgreSQL integration, SQL functions
• Go Layer: Raft consensus engine (etcd-io/raft)
• Storage: Persistent state on disk
• Network: TCP server for inter-node communication

For detailed architecture, see the Architecture Guide.

Split-Brain Protection

pgraft provides 100% split-brain protection through Raft consensus:

• Quorum Requirement: Leader needs majority votes (N/2 + 1)
• Term Monotonicity: Higher term always wins
• Single Leader Per Term: Mathematical guarantee

For a 3-node cluster:

• Minimum 2 votes required for election
• Network partition: Only majority side can elect leader
• Impossible to have 2 leaders in same term

Learn more: Split-Brain Protection Guide

Examples

Three-Node Cluster

Configure each node with unique node_id:

shared_preload_libraries = 'pgraft'
pgraft.cluster_id = 'prod-cluster'
pgraft.node_id = 1  # 2, 3 for other nodes
pgraft.address = '127.0.0.1'
pgraft.port = 7001  # 7002, 7003 for other nodes

Then initialize:

# On each node
psql -c "CREATE EXTENSION pgraft; SELECT pgraft_init();"

# On leader (after 10 seconds)
psql -c "SELECT pgraft_add_node(2, '127.0.0.1', 7002);"
psql -c "SELECT pgraft_add_node(3, '127.0.0.1', 7003);"

For complete examples and test harness, see the Tutorial.

Monitoring

Quick health check:

SELECT 
    pgraft_is_leader() as is_leader,
    pgraft_get_term() as term,
    pgraft_get_leader() as leader_id,
    pgraft_get_worker_state() as worker;

For comprehensive monitoring guide, see Monitoring.

Troubleshooting

Common issues:

• Worker not running: Check shared_preload_libraries includes 'pgraft'
• Cannot add node: Must run on leader node
• No leader elected: Wait 10 seconds, check network connectivity

For complete troubleshooting guide, see Troubleshooting.

Development

Build and test:

# Build
make clean && make

# Test
cd examples
./run.sh --destroy && ./run.sh --init

For development guide, see Development.

Performance

• Tick Interval: 100ms (worker-driven)
• Election Timeout: 1000ms (default, configurable)
• Heartbeat: 100ms (default, configurable)
• Memory: ~50MB per node
• CPU: <1% idle, <5% during elections

Architecture

pgraft uses a worker-driven architecture where a PostgreSQL background worker drives the Raft consensus engine implemented in Go using etcd-io/raft.

For detailed architecture information, see the Architecture Guide.

License

MIT License - see LICENSE file for details.

Documentation

Complete documentation is available at: https://pgelephant.github.io/pgraft/

Documentation Sections

• Getting Started - Installation and quick start
• User Guide - Complete tutorial and configuration
• Core Concepts - Architecture and algorithms
• Operations - Monitoring and best practices
• Development - Building and contributing

Community and Support

• Documentation: https://pgelephant.github.io/pgraft/
• Issues: GitHub Issues
• Contributing: CONTRIBUTING.md
• License: MIT License

Project Status

Status: Production Ready
Version: 1.0.0
Standards: 100% PostgreSQL C Compliant
Quality: 0 compilation errors/warnings

Related Projects

• etcd-io/raft - Raft consensus implementation used by pgraft
• PostgreSQL - The world's most advanced open source database
• RAM - PostgreSQL clustering and failover manager
• RALE - Distributed consensus and key-value store
• FauxDB - MongoDB-compatible query proxy for PostgreSQL

SEO/Discoverability keywords

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