Distributed State Machine

A Rust implementation of a distributed state machine using a consensus protocol for state synchronization across nodes. The system uses a proposal-acknowledgment-commit pattern to ensure consistent state transitions across the network.

Features

• Distributed consensus protocol
• State transition validation
• Retry mechanism for message delivery
• Metrics collection
• Asynchronous communication using Tokio
• Comprehensive error handling
• Test coverage including unit and integration tests

Architecture

The system consists of the following key components:

• Node: Main component that handles peer communication and state management
• State Machine: Supports three states (Init, Running, Stopped) with validated transitions
• Message Types:
  • Proposal: Initiates state change
  • Acknowledgment: Confirms receipt of proposal
  • Commit: Finalizes state change
  • Reject: Declines invalid state transitions

Implementation Details

State Transitions

The system enforces strict state transition rules:

• Init → Running
• Running → Stopped
• Stopped → Init

Any other state transitions are considered invalid and will be rejected.

Message Flow

1. A node initiates a state change by broadcasting a proposal
2. Peer nodes validate the proposal and respond with acknowledgments
3. Once majority consensus is reached, the proposing node broadcasts a commit
4. All nodes apply the state change upon receiving the commit message

Error Handling

The system includes comprehensive error handling for:

• Network failures
• Serialization errors
• Consensus timeouts
• Message delivery failures

Retry Mechanism

• Configurable retry attempts for message delivery
• Adjustable delay between retry attempts
• Metrics tracking for successful/failed message delivery

Configuration

The system supports configurable parameters including:

• Consensus timeout duration
• Message retry attempts
• Message retry delay intervals

Metrics and Monitoring

Built-in metrics collection for:

• Message success/failure rates
• Node count
• Message processing statistics

Testing

The implementation includes extensive testing:

• Unit tests for state transitions
• Message handling tests
• Integration tests for node communication
• Mock network implementations for testing
• Timeout and error condition testing

Technical Requirements

• Rust (latest stable version)
• Tokio for async runtime
• Serde for serialization
• Metrics for monitoring
• Tracing for logging

Network Communication

The system uses TCP for reliable communication between nodes:

• Asynchronous message handling
• JSON serialization for messages
• Built-in connection management
• Automatic reconnection handling

Future Enhancements

• Message authentication (signature verification)
• Dynamic peer discovery
• State persistence
• Enhanced security features
• Performance optimizations