@openstatus/health-memory

Memory probe for @openstatus/health. Compares the process's heap in use with the V8 heap limit — and its resident set size with a byte budget — and fails the check above either threshold, so a leak turns the report degraded before the process is killed for running out of memory.

deno add jsr:@openstatus/health jsr:@openstatus/health-memory
npm install @openstatus/health @openstatus/health-memory

import { createHealthHandler } from "@openstatus/health";
import { memoryProbe } from "@openstatus/health-memory";

Deno.serve(
  createHealthHandler({
    probes: [memoryProbe({ maxHeapUsedPercent: 90 })],
  }),
);

The heap percentage is heapUsed from process.memoryUsage() over heap_size_limit from v8.getHeapStatistics() — the limit V8 will actually grow to, which honours --max-old-space-size. It is the number that predicts an out-of-memory crash. maxRssBytes bounds the whole resident set instead, which is what a container limit or an OOM killer measures; set it a little under that limit. The check fails above maxHeapUsedPercent (90% by default) or above maxRssBytes when that is set instead; pass both to enforce both. A failing check throws MemoryPressureError, which carries the reading, and a healthy one reports heapUsedBytes, heapLimitBytes, heapUsedPercent and rssBytes.

memoryProbe({
  maxHeapUsedPercent: 85,
  maxRssBytes: 900 * 1024 * 1024,
  // optional overrides from the Probe contract
  name: "heap",
  critical: true,
  timeoutMs: 100,
  skip: () => env.NODE_ENV !== "production",
});

Non-critical by default: memory pressure is an alert to act on, and taking a leaking instance out of rotation only shifts its traffic onto the others. Set critical: true when your platform restarts unhealthy instances and that is the recovery you want.

This probe uses node:process and node:v8, so it runs on Node.js, Deno and Bun but not on edge runtimes. Both readers are typed structurally and can be replaced for tests.

About openstatus

openstatus is the open-source uptime monitoring and status page platform. This package is part of @openstatus/health, the /health endpoints behind openstatus's own services, extracted so any JavaScript server can expose one. Point an openstatus monitor at the endpoint and assert on status in the body to be alerted on degraded before it becomes unhealthy.

Source: github.com/openstatusHQ/health. Issues and PRs welcome.

License

MIT