[AIR-3][AIS-3][BPC-3][RES-3]

High Availability System [AIR-3][AIS-3][RES-3][SCL-3]¶

Table of Contents¶

• Section 1
• Section 2

This document describes the High Availability (HA) subsystem of Anya Core, detailing the architecture, components, and operational characteristics that ensure continuous operation even in the face of failures.

Overview¶

The High Availability subsystem provides fault tolerance, automatic failover, and resilience capabilities to Anya Core. It implements a distributed coordination mechanism that ensures service continuity even when individual nodes or components fail.

Architecture¶

The HA system follows the hexagonal architecture pattern defined by official Bitcoin Improvement Proposals (BIPs):

                  +----------------+
                  | Cluster API    |
                  +-------+--------+
                          |
+----------------+  +-----v--------+  +----------------+
|   Discovery    |  |   Cluster    |  |   Monitoring   |
|   Services     <--+   Manager    +-->   & Metrics    |
| (DNS, K8s, etc)|  |              |  | (Prometheus)   |
+----------------+  +-------+------+  +----------------+
                          |
                  +-------v--------+
                  | Node Management|
                  | & Health Checks|
                  +----------------+

Key Components [AIR-3]¶

Cluster Manager¶

The ClusterManager is the central component of the High Availability subsystem. It manages:

• Node discovery and registration
• Leader election
• Health monitoring
• Fault detection
• Automatic failover
• Configuration synchronization

/// Cluster Manager for high availability operations
/// \[AIR-3\]\[RES-3\]\[SCL-3\]
pub struct ClusterManager {
    config: ClusterConfig,
    nodes: HashMap<NodeId, NodeInfo>,
    current_leader: Option<NodeId>,
    status: ClusterStatus,
}

Node Discovery Services [AIR-3]¶

Multiple node discovery mechanisms are supported:

1. Static Configuration: Pre-configured list of nodes
2. DNS Discovery: SRV record-based discovery
3. Kubernetes Discovery: Kubernetes API-based discovery
4. Multicast Discovery: Local network discovery via multicast

Membership Service [RES-3]¶

The Membership Service tracks node status and manages:

• Node join/leave operations
• Health check protocols
• Heartbeat monitoring
• Split-brain detection
• Quorum-based decisions

Health Monitoring [RES-3]¶

Comprehensive health monitoring includes:

• Regular heartbeat checks
• Application-level health probes
• Resource utilization monitoring
• Response time measurements
• Error rate tracking

Leader Election [AIR-3][RES-3]¶

The leader election algorithm is based on the Raft consensus protocol with the following properties:

1. Safety: At most one leader can be elected in a given term
2. Liveness: A new leader will eventually be elected if the current one fails
3. Fault Tolerance: The system can tolerate up to (N-1)/2 node failures

The election process follows these steps:

1. All nodes start in follower state
2. If a follower receives no communication, it becomes a candidate
3. A candidate requests votes from other nodes
4. Nodes vote for at most one candidate per term
5. A candidate becomes the leader if it receives votes from a majority of nodes

Fault Detection and Recovery [RES-3]¶

The system detects and handles various failure scenarios:

Failure Type	Detection Method	Recovery Action
Node Crash	Missed heartbeats	Leader election
Network Partition	Quorum loss	Partition healing
Performance Degradation	Slow response time	Load balancing
Resource Exhaustion	Resource metrics	Auto-scaling
Application Errors	Error rate increase	Restart service

Configuration Synchronization [AIR-3]¶

The HA subsystem ensures configuration consistency across the cluster:

1. Leader maintains the authoritative configuration
2. Configuration changes are propagated to all nodes
3. Version tracking prevents conflicts
4. Two-phase commit ensures atomic updates
5. Roll-back capability for failed updates

Security Considerations [AIS-3]¶

The HA system implements these security measures:

1. TLS Mutual Authentication: All node-to-node communication is encrypted and authenticated
2. Authorization: Role-based access control for administrative operations
3. Audit Logging: All cluster operations are logged with tamper-evident records
4. Network Isolation: Control plane traffic is isolated from data plane
5. Secure Bootstrap: Nodes are securely provisioned with initial credentials

Performance Characteristics [AIP-3]¶

The HA subsystem is designed for optimal performance:

• Low-latency leader election (<500ms in typical conditions)
• Efficient heartbeat protocol with minimal network overhead
• Scalable to 100+ nodes without significant performance degradation
• Configurable monitoring intervals based on deployment requirements
• Low CPU and memory footprint (<5% of system resources)

Bitcoin-Specific Considerations [AIR-3][AIS-3]¶

For Bitcoin operations, the HA system provides additional guarantees:

1. Transaction Consistency: Ensures no double-spending during failover
2. UTXO Set Integrity: Maintains consistent UTXO references across nodes
3. Blockchain State: Synchronizes blockchain view across all nodes
4. HSM Coordination: Manages distributed HSM operations securely
5. DLC Contract Continuity: Ensures DLC contracts remain valid during failover

Usage Examples¶

Basic HA Cluster Configuration¶

let config = ClusterConfig {
    node_id: "node-1".to_string(),
    discovery_method: DiscoveryMethod::Static {
        nodes: vec!["node-1:7800".to_string(), "node-2:7800".to_string(), "node-3:7800".to_string()],
    },
    bind_address: "0.0.0.0:7800".to_string(),
    heartbeat_interval: Duration::from_secs(1),
    election_timeout: Duration::from_secs(5),
    ..Default::default()
};

let cluster_manager = ClusterManager::new(config);
cluster_manager.initialize().await?;
cluster_manager.join_cluster().await?;

// Get cluster status
let status = cluster_manager.get_status().await?;
println!("Current leader: {:?}", status.current_leader);
println!("Cluster nodes: {:?}", status.nodes);

Custom Health Check Configuration¶

let health_config = HealthCheckConfig {
    checks: vec![
        HealthCheck::Http {
            name: "api".to_string(),
            url: "http://localhost:8080/health".to_string(),
            interval: Duration::from_secs(5),
            timeout: Duration::from_secs(1),
            expected_status: 200,
        },
        HealthCheck::Custom {
            name: "bitcoin-sync".to_string(),
            command: Box::new(|ctx| {
                Box::pin(async move {
                    // Check Bitcoin synchronization status
                    let bitcoin_client = ctx.get_service::<BitcoinClient>().unwrap();
                    let sync_status = bitcoin_client.get_sync_status().await?;
                    Ok(sync_status.blocks_remaining < 10)
                })
            }),
            interval: Duration::from_secs(30),
        },
    ],
    aggregation: HealthAggregation::All,
};

cluster_manager.configure_health_checks(health_config).await?;

Testing and Verification [AIT-3]¶

The HA subsystem undergoes rigorous testing:

1. Unit Tests: All components have comprehensive unit tests
2. Chaos Testing: Random node failures are simulated
3. Network Partition Testing: Various network partition scenarios
4. Performance Testing: Behavior under load and stress conditions
5. Long-running Tests: Stability verification over extended periods

Future Enhancements¶

Planned improvements to the HA subsystem include:

1. Geo-distributed Clustering: Support for multi-region deployments
2. Automatic Scaling: Dynamic node addition/removal based on load
3. Enhanced Observability: Advanced metrics and diagnostics
4. Custom Consensus Protocols: Pluggable consensus mechanisms
5. Integrated Backup Management: Automated backup and restore

References¶

1. Official Bitcoin Improvement Proposals (BIPs)
2. Raft Consensus Algorithm
3. Kubernetes Operator Framework
4. Prometheus Monitoring System
5. BFT Consensus Algorithms

Last Updated¶

2025-03-12

See Also¶

• Related Document