replication

Replication Documentation Index

Welcome to the ThemisDB replication documentation. This directory serves as the central hub for all replication and high-availability (HA) documentation.

📚 Core Documentation

User Guides

• replication-ha-guide.md - START HERE ⭐
  • Complete guide to High Availability replication
  • Deployment topologies (Active-Passive, Active-Active, Multi-DC)
  • Configuration examples and best practices
  • Monitoring, alerting, and operational procedures
  • Performance tuning and troubleshooting

Implementation Documentation

• REPLICATION_IMPLEMENTATION_STATUS.md (German)

  • Detailed implementation status (~85% complete)
  • Component breakdown and file locations
  • Write-path flow diagrams
  • Build & test status
  • Prometheus metrics reference

• replication_raid_plan.md

  • RAID 1/10 replication readiness plan
  • Current findings and implementation steps
  • Acceptance criteria and next actions
  • Integration status

🏗️ Architecture Overview

Module Organization

ThemisDB's replication system is organized across two main modules:

replication/ Module (High-Level Orchestration)

• Location: include/replication/, src/replication/
• Components:
  • ReplicationManager - Lifecycle and configuration management
  • MultiMasterReplicationManager - Multi-master coordination (see include/replication/multi_master_replication.h)
• Responsibility: High-level replication strategies and orchestration

sharding/ Module (Low-Level Infrastructure)

• Location: include/sharding/, src/sharding/
• Components:
  • WALManager - Write-Ahead Log with LSN tracking
  • WALShipper - Batch-based WAL shipping to replicas
  • WALApplier - Idempotent WAL application
  • ReplicationCoordinator - Write concern enforcement (ONE/MAJORITY/ALL)
  • ReplicaTopology - Shard-to-replica mapping (RAID 1/10/5/6)
  • Consensus modules (Raft, Gossip, Paxos)
  • HealthMonitor - Replica health tracking
• Responsibility: WAL-based replication mechanics, distributed consensus, topology management

Design Rationale: This separation allows the replication/ module to focus on business logic while sharding/ handles the complex distributed systems infrastructure needed for both replication and horizontal scaling.

Key Features

✅ Completed:

• WAL-based replication with LSN tracking
• Write concern support (ONE/MAJORITY/ALL)
• RAID 1/10 topology support
• Idempotent WAL application
• Prometheus metrics integration
• HTTP and gRPC replication endpoints
• Leader election (Raft/Gossip/Paxos)
• Health monitoring and failure detection

🚧 In Progress:

• Multi-node endurance testing
• RAID 5/6 implementation
• Automatic failover enhancement

🔗 Related Documentation

Sharding & Distribution

• Distributed Sharding Architecture
• Consensus Module Architecture
• Distributed Transactions

System Architecture

• ARCHITECTURE.md - System overview
• SECURITY.md - Security configuration
• MONITORING.md - Monitoring setup

Operations

• Disaster Recovery - DR procedures

🚀 Quick Start

1. Start here: Read replication-ha-guide.md for a comprehensive overview
2. Configuration: Check the configuration examples in the HA guide
3. Implementation details: See REPLICATION_IMPLEMENTATION_STATUS.md for component-level details
4. Deployment planning: Review replication_raid_plan.md for RAID configuration

📊 Implementation Status

Overall Progress: ~85% Complete

Completed Components ✅

• WAL Manager, Shipper, Applier
• Replication Coordinator
• Replica Topology
• HTTP/gRPC endpoints
• Integration tests (8/8 passing)
• Prometheus metrics

Remaining Work

• Multi-node endurance testing
• RAID 5/6 parity implementation
• Automatic failover enhancements

🤝 Contributing

When updating replication documentation:

1. Keep all three core documents in sync (HA guide, implementation status, RAID plan)
2. Update cross-references when adding new documentation
3. Follow the established structure for consistency
4. Update this index when adding new replication docs

📝 License

See LICENSE for licensing information.