HugeGraph Store

Note: From revision 1.5.0, the HugeGraph-Store code has been adapted to this location.

Overview

HugeGraph Store is a distributed storage backend for HugeGraph that provides high availability, horizontal scalability, and strong consistency for production graph database deployments. Built on RocksDB and Apache JRaft, it serves as the data plane for large-scale graph workloads requiring enterprise-grade reliability.

Core Capabilities

• Distributed Storage: Hash-based partitioning with automatic data distribution across multiple Store nodes
• High Availability: Multi-replica data replication using Raft consensus, tolerating node failures without data loss
• Horizontal Scalability: Dynamic partition allocation and rebalancing for seamless cluster expansion
• Query Optimization: Advanced query pushdown (filter, aggregation, index) and multi-partition parallel execution
• Metadata Coordination: Tight integration with HugeGraph PD for cluster management and service discovery
• High Performance: gRPC-based communication with streaming support for large result sets

Technology Stack

• Storage Engine: RocksDB 7.7.3 (optimized for graph workloads)
• Consensus Protocol: Apache JRaft (Ant Financial's Raft implementation)
• RPC Framework: gRPC + Protocol Buffers
• Deployment: Java 11+, Docker/Kubernetes support

When to Use HugeGraph Store

Use Store for:

• Production deployments requiring high availability (99.9%+ uptime)
• Workloads exceeding single-node storage capacity (100GB+)
• Multi-tenant or high-concurrency scenarios (1000+ QPS)
• Environments requiring horizontal scalability and fault tolerance

Use RocksDB Backend for:

• Development and testing environments
• Single-node deployments with moderate data size (<100GB)
• Embedded scenarios where simplicity is preferred over distribution

Architecture

HugeGraph Store is a Maven multi-module project consisting of 9 modules:

Three-Tier Architecture

Client Layer (hugegraph-server)
    ↓ (hg-store-client connects via gRPC)
Store Node Layer (hg-store-node)
    ├─ gRPC Services (Session, Query, State)
    ├─ Partition Engines (each partition = one Raft group)
    └─ PD Integration (heartbeat, partition assignment)
         ↓
Storage Engine Layer (hg-store-core + hg-store-rocksdb)
    ├─ HgStoreEngine (manages all partition engines)
    ├─ PartitionEngine (per-partition Raft state machine)
    └─ RocksDB (persistent storage)

Key Architectural Features

• Partition-based Distribution: Data is split into partitions (default: hash-based) and distributed across Store nodes
• Raft Consensus per Partition: Each partition is a separate Raft group with 1-3 replicas (typically 3 in production)
• PD Coordination: Store nodes register with PD for partition assignment, metadata synchronization, and health monitoring
• Query Pushdown: Filters, aggregations, and index scans are pushed to Store nodes for parallel execution

For detailed architecture, Raft consensus mechanisms, and partition management, see Distributed Architecture.

Quick Start

Prerequisites

• Java: 11 or higher
• Maven: 3.5 or higher
• HugeGraph PD Cluster: Store requires a running PD cluster for metadata coordination (see PD README)
• Disk Space: At least 10GB per Store node for data and Raft logs
• Network: Low-latency network (<5ms) between Store nodes for Raft consensus

Build

Important: Build hugegraph-struct first, as it's a required dependency.

From the project root:

# Build struct module
mvn install -pl hugegraph-struct -am -DskipTests

# Build Store and all dependencies
mvn clean package -pl hugegraph-store/hugegraph-store-dist -am -DskipTests

The assembled distribution will be available at:

hugegraph-store/apache-hugegraph-store-incubating-1.7.0/lib/hg-store-node-1.7.0.jar```

Configuration

Extract the distribution package and edit conf/application.yml:

Core Settings

Single-Node Development Example (with fake-pd)

pdserver:
  address: localhost:8686  # Ignored when fake-pd is true

grpc:
  host: 127.0.0.1
  port: 8500

raft:
  address: 127.0.0.1:8510
  snapshotInterval: 1800

server:
  port: 8520

app:
  data-path: ./storage
  fake-pd: true  # Built-in PD mode (development only)

3-Node Cluster Example (production)

Prerequisites: A running 3-node PD cluster at 192.168.1.10:8686, 192.168.1.11:8686, 192.168.1.12:8686

Store Node 1 (192.168.1.20):

pdserver:
  address: 192.168.1.10:8686,192.168.1.11:8686,192.168.1.12:8686

grpc:
  host: 192.168.1.20
  port: 8500

raft:
  address: 192.168.1.20:8510

app:
  data-path: ./storage
  fake-pd: false

Store Node 2 (192.168.1.21):

pdserver:
  address: 192.168.1.10:8686,192.168.1.11:8686,192.168.1.12:8686

grpc:
  host: 192.168.1.21
  port: 8500

raft:
  address: 192.168.1.21:8510

app:
  data-path: ./storage
  fake-pd: false

Store Node 3 (192.168.1.22):

pdserver:
  address: 192.168.1.10:8686,192.168.1.11:8686,192.168.1.12:8686

grpc:
  host: 192.168.1.22
  port: 8500

raft:
  address: 192.168.1.22:8510

app:
  data-path: ./storage
  fake-pd: false

For detailed configuration options, RocksDB tuning, and deployment topologies, see Deployment Guide.

Run

Start the Store server:

# Replace {version} with your hugegraph version
cd apache-hugegraph-store-incubating-{version}

# Start Store node
bin/start-hugegraph-store.sh

# Stop Store node
bin/stop-hugegraph-store.sh

# Restart Store node
bin/restart-hugegraph-store.sh

Startup Options

bin/start-hugegraph-store.sh [-g GC_TYPE] [-j "JVM_OPTIONS"]

• -g: GC type (g1 or ZGC, default: g1)
• -j: Custom JVM options (e.g., -j "-Xmx16g -Xms8g")

Default JVM memory settings (defined in start-hugegraph-store.sh):

• Max heap: 32GB
• Min heap: 512MB

Verify Deployment

Check if Store is running and registered with PD:

# Check process
ps aux | grep hugegraph-store

# Test gRPC endpoint (requires grpcurl)
grpcurl -plaintext localhost:8500 list

# Check REST API health
curl http://localhost:8520/v1/health

# Check logs
tail -f logs/hugegraph-store.log

# Verify registration with PD (from PD node)
curl http://localhost:8620/v1/stores

For production deployment, see Deployment Guide and Best Practices.

Integration with HugeGraph Server

HugeGraph Store serves as a pluggable backend for HugeGraph Server. To use Store as the backend:

1. Configure HugeGraph Server Backend

Edit hugegraph-server/conf/graphs/<graph-name>.properties:

# Backend configuration
backend=hstore
serializer=binary

# Store connection (PD addresses)
store.provider=org.apache.hugegraph.backend.store.hstore.HstoreProvider
store.pd_peers=192.168.1.10:8686,192.168.1.11:8686,192.168.1.12:8686

# Connection pool settings
store.max_sessions=4
store.session_timeout=30000

2. Start HugeGraph Server

Ensure PD and Store clusters are running, then start HugeGraph Server:

cd hugegraph-server
bin/init-store.sh  # Initialize schema
bin/start-hugegraph.sh

3. Verify Backend

# Check backend via REST API
curl --location --request GET 'http://localhost:8080/metrics/backend' \
--header 'Authorization: Bearer <YOUR_ACCESS_TOKEN>'
# Response should show:
# {"backend": "hstore", "nodes": [...]}

Testing

Run Store tests:

# All tests (from hugegraph root)
mvn test -pl hugegraph-store/hg-store-test -am

# Specific test module
mvn test -pl hugegraph-store/hg-store-test -am -Dtest=HgStoreEngineTest

# From hugegraph-store directory
cd hugegraph-store
mvn test

Test Profiles

Store tests are organized into 6 profiles (all active by default):

• store-client-test: Client library tests
• store-core-test: Core storage and partition management tests
• store-common-test: Common utilities and query abstraction tests
• store-rocksdb-test: RocksDB abstraction layer tests
• store-server-test: Store node server and gRPC service tests
• store-raftcore-test: Raft consensus integration tests

For development workflows and debugging, see Development Guide.

Docker

Build Docker Image

From the project root:

docker build -f hugegraph-store/Dockerfile -t hugegraph-store:latest .

Run Container

docker run -d \
  -p 8520:8520 \
  -p 8500:8500 \
  -p 8510:8510 \
  -v /path/to/conf:/hugegraph-store/conf \
  -v /path/to/storage:/hugegraph-store/storage \
  -e PD_ADDRESS=192.168.1.10:8686,192.168.1.11:8686 \
  --name hugegraph-store \
  hugegraph-store:latest

Exposed Ports:

• 8520: REST API (management, metrics)
• 8500: gRPC (client connections)
• 8510: Raft consensus

Docker Compose Example

For a complete HugeGraph distributed deployment (PD + Store + Server), see:

hugegraph-server/hugegraph-dist/docker/example/

For Docker and Kubernetes deployment details, see Deployment Guide.

Documentation

Comprehensive documentation for HugeGraph Store:

Production Deployment Notes

Cluster Topology

Minimum Cluster (development/testing):

• 3 PD nodes
• 3 Store nodes
• 1-3 Server nodes

Recommended Production Cluster:

• 3-5 PD nodes (odd number for Raft quorum)
• 6-12 Store nodes (depends on data size and throughput)
• 3-6 Server nodes (depends on query load)

Large-Scale Cluster:

• 5 PD nodes
• 12+ Store nodes (horizontal scaling)
• 6+ Server nodes (load balancing)

High Availability

• Store uses Raft consensus for leader election and data replication
• Each partition has 1-3 replicas (default: 3 in production)
• Cluster can tolerate up to (N-1)/2 Store node failures per partition (e.g., 1 failure in 3-replica setup)
• Automatic failover and leader re-election (typically <10 seconds)
• PD provides cluster-wide coordination and metadata consistency

Partition Strategy

• Default Partitioning: Hash-based (configurable in PD)
• Partition Count: Recommended 3-5x the number of Store nodes for balanced distribution
• Replica Count: 3 replicas per partition for production (configurable)
• Rebalancing: Automatic partition rebalancing triggered by PD patrol (default: 30 minutes interval)

Network Requirements

• Latency: <5ms between Store nodes for Raft consensus performance
• Bandwidth: 1Gbps+ recommended for data replication and query traffic
• Ports: Ensure firewall allows traffic on 8500 (gRPC), 8510 (Raft), 8520 (REST)
• Topology: Consider rack-aware or availability-zone-aware placement for fault isolation

Monitoring

Store exposes metrics via:

• REST API: http://<store-host>:8520/actuator/metrics
• Health Check: http://<store-host>:8520/actuator/health
• Prometheus Integration: Metrics exported in Prometheus format

Key Metrics to Monitor:

• Raft leader election count and duration
• Partition count and distribution
• RocksDB read/write latency and throughput
• gRPC request QPS and error rate
• Disk usage and I/O metrics

For detailed operational guidance, see Operations Guide and Best Practices.

Community

• Website: https://hugegraph.apache.org
• Documentation: https://hugegraph.apache.org/docs/
• GitHub: https://github.com/apache/hugegraph
• Mailing List: dev@hugegraph.apache.org
• Issue Tracker: https://github.com/apache/hugegraph/issues

Contributing

Contributions are welcome! Please read our Development Guide and follow the Apache HugeGraph contribution guidelines.

For development workflows, code structure, and testing strategies, see the Development Guide.

License

HugeGraph Store is licensed under the Apache License 2.0.

HugeGraph Store is under active development. Please report issues via GitHub or the mailing list.