Circuit breaker pattern for backend protection.

Prevents cascade failures by automatically stopping traffic to backends
that are experiencing high error rates, allowing them time to recover.

State Machine:
- CLOSED (normal): Traffic flows, errors are counted
- OPEN (blocking): No traffic sent, waiting for timeout
- HALF-OPEN (testing): Limited traffic to test recovery

Transitions:
- CLOSED -> OPEN: When error rate exceeds threshold
- OPEN -> HALF-OPEN: After open-duration-ms timeout
- HALF-OPEN -> CLOSED: After N consecutive successes
- HALF-OPEN -> OPEN: On any failure

Configuration management for the load balancer.
Handles configuration data structures, validation, and persistence.

Connection tracking management for the load balancer.
Provides utilities for monitoring, cleaning, and querying connection state.

Core API for the eBPF load balancer.
Provides high-level functions for initialization, configuration, and management.

DNS-based backend resolution for dynamic environments.

Provides:
- DNS hostname support for backend targets
- Periodic re-resolution with configurable intervals
- Multiple A record expansion to weighted targets
- Graceful failure handling with last-known-good fallback

Usage:
  ;; In configuration
  :default-target {:host "backend.local" :port 8080 :dns-refresh-seconds 30}

  ;; Programmatic usage
  (dns/start!)
  (dns/register-target! "proxy-name" "hostname" config update-fn)
  (dns/get-status "proxy-name")
  (dns/stop!)

Background daemon for periodic DNS re-resolution.

Follows the same pattern as lb.health.manager:
- ScheduledExecutorService for periodic tasks
- Jitter to avoid thundering herd
- Callbacks to update BPF maps on IP changes
- Last-known-good fallback on failures

DNS resolution logic with multiple A record support.

Provides:
- Resolution of hostnames to all A records
- Conversion of resolved IPs to weighted targets
- Result types for success/failure handling

Connection draining for graceful backend removal.
Allows backends to be drained by stopping new connections while
allowing existing connections to complete.

Public API for health checking system.
Provides a simple interface for managing health-aware load balancing.

Health check implementations for TCP and HTTP protocols.
Uses virtual threads for efficient concurrent checking.

Health check orchestration using virtual threads.
Manages health state for all targets and triggers weight updates.

Weight redistribution logic for health-aware load balancing.
Computes effective weights based on target health status.

eBPF map management for the load balancer.
Provides functions to create, operate on, and close all required maps.

Prometheus metrics export for the load balancer.

Provides an HTTP endpoint for Prometheus scraping with metrics:
- lb_connections_active - Current active connections
- lb_bytes_total - Bytes transferred (forward/reverse)
- lb_packets_total - Packets transferred
- lb_backend_health - Backend health status (0/1)
- lb_health_check_latency_seconds - Health check latency histogram
- lb_dns_resolution_status - DNS resolution status

Usage:
  ;; In configuration
  :settings {:metrics {:enabled true :port 9090 :path "/metrics"}}

  ;; Programmatic usage
  (metrics/start! {:port 9090})
  (metrics/register-data-sources! {...})
  (metrics/stop!)

Collects and formats metrics in Prometheus text format.

Gathers data from various sources:
- Connection tracking (active connections, bytes, packets)
- Health checking (backend health status, latency)
- DNS resolution (resolution status)
- Stats aggregator (totals)

Histogram implementation for Prometheus metrics.

Provides cumulative bucket histograms compatible with Prometheus format.

HTTP server for Prometheus metrics endpoint.

Provides a simple HTTP server using Java's built-in HttpServer
that serves Prometheus-formatted metrics on a configurable endpoint.

Common eBPF program fragments and DSL utilities shared between XDP and TC programs.

TC egress program for the load balancer.
Handles reply packets from backends: performs SNAT to restore original destination.

XDP ingress program for the load balancer.
Handles incoming packets: parses headers, looks up routing, performs DNAT.

Rate limiting management for the load balancer.

Provides per-source IP and per-backend rate limiting using a token bucket
algorithm. Rate limits are configured via BPF maps and enforced in the
XDP program.

Token bucket parameters:
- rate: tokens added per second (requests/sec)
- burst: maximum tokens (handles traffic spikes)

Rate limiting is disabled by default (rate = 0).

Configuration hot reload for the load balancer.

Provides:
- File watching (inotify-based via Java NIO WatchService)
- SIGHUP signal handling
- Incremental configuration updates
- Validation before apply with rollback on failure

Usage:
  ;; Enable hot reload for a config file
  (enable-hot-reload! "/etc/lb/config.edn")

  ;; Manual reload
  (reload-config!)

  ;; Disable hot reload
  (disable-hot-reload!)

Statistics streaming and aggregation for the load balancer.
Consumes events from the eBPF ring buffer and provides real-time stats.

Utility functions for IP address conversion, CIDR parsing, and binary encoding.