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Health checks

createCovara mounts two endpoints by default:

EndpointProbeMeaning
GET /healthzLivenessThe process is up. Stays 200 even during graceful shutdown.
GET /readyzReadinessThe instance is ready to serve traffic. Flips to 503 during shutdown so load balancers drain it.

Both support HEAD for cheap probes. Wire them into your orchestrator (Kubernetes livenessProbe/readinessProbe, load-balancer health checks).

Configuration​

const app = createCovara({
  health: {
    version: "1.0.0",
    checks: {
      kv: getGlobalKV(),         // dependency checks — included in the readiness result
    },
    thresholds: {
      eventLoopLagMs: 100,        // mark unhealthy above this lag
      memoryPercent: 90,          // mark unhealthy above this memory usage
    },
  },
});

Pass health: false to disable the endpoints, or health: true for defaults.

checks accepts dependency objects (e.g. the KV store, a database) that the readiness endpoint probes; a failing dependency makes /readyz report unhealthy. thresholds add runtime guards (event-loop lag, memory) on Node.

Response shape​

{
  "status": "ok",
  "version": "1.0.0",
  "uptime": 3600,
  "checks": { "kv": { "status": "ok" } }
}

Graceful shutdown​

On Node, startServer installs SIGTERM/SIGINT handlers that, on shutdown:

  1. flip readiness so /readyz returns 503 (new traffic stops routing here),
  2. close long-lived SSE subscriptions cleanly so clients reconnect elsewhere,
  3. wait a bounded drain window (drainTimeoutMs, default 10s) before closing the listener.

/healthz stays 200 throughout — only /readyz flips — so the orchestrator distinguishes "draining" from "dead". See Node deployment.