Module peer 

Peer connection management.

Manages Redis connections to peer nodes with automatic reconnection, circuit breaker protection, and Merkle root caching.

Connection Lifecycle

Disconnected → Connecting → Connected
     ↑             ↓             ↓
     └─── Backoff ←┴─────────────┘

Connections are lazy: they’re only established when first needed (via PeerConnection::ensure_connected()). If a connection fails, the peer enters PeerState::Backoff state with exponential backoff.

Circuit Breaker

Each peer has a circuit breaker to prevent cascade failures:

• Closed: Normal operation, requests pass through
• Open: Too many consecutive failures, requests rejected immediately

The circuit opens after circuit_failure_threshold consecutive failures and resets after circuit_reset_timeout_sec seconds.

Merkle Root Caching

To reduce load during cold path repair, Merkle roots are cached for 5 seconds (see MERKLE_ROOT_CACHE_TTL). This prevents hammering peers when checking consistency.

Example

use replication_engine::peer::PeerConnection;
use replication_engine::config::PeerConfig;

let config = PeerConfig::for_testing("peer-1", "redis://localhost:6379");
let peer = PeerConnection::new(config);

// Connection is lazy - this triggers the actual connect
peer.ensure_connected().await?;

// Use the connection
let conn = peer.connection().await;

Structs

PeerConnection

A managed connection to a peer’s Redis.

PeerManager

Manager for all peer connections.

Enums

PeerCircuitState

Circuit breaker state for peer connections.

PeerState

State of a peer connection.