lib/metrics/runtime.js

/*
 * Copyright Elasticsearch B.V. and other contributors where applicable.
 * Licensed under the BSD 2-Clause License; you may not use this file except in
 * compliance with the BSD 2-Clause License.
 */

'use strict';

const eventLoopMonitor = require('monitor-event-loop-delay');

const activeHandles =
  typeof process._getActiveHandles === 'function'
    ? process._getActiveHandles.bind(process)
    : () => [];

const activeRequests =
  typeof process._getActiveRequests === 'function'
    ? process._getActiveRequests.bind(process)
    : () => [];

const eventLoopMonitorResolution = 10;

class RuntimeCollector {
  constructor() {
    this.stats = {
      'nodejs.handles.active': 0,
      'nodejs.requests.active': 0,
      'nodejs.eventloop.delay.avg.ms': 0,
      'nodejs.memory.heap.allocated.bytes': 0,
      'nodejs.memory.heap.used.bytes': 0,
      'nodejs.memory.external.bytes': 0,
      'nodejs.memory.arrayBuffers.bytes': 0,
    };

    const monitor = eventLoopMonitor({
      resolution: eventLoopMonitorResolution,
    });
    monitor.enable();

    this.loopMonitor = monitor;
    this.collect();
  }

  collect(cb) {
    // Handles and Requests
    this.stats['nodejs.handles.active'] = activeHandles().length;
    this.stats['nodejs.requests.active'] = activeRequests().length;

    // Event loop
    const loopDelay = Math.max(
      0,
      (this.loopMonitor.mean || 0) / 1e6 - eventLoopMonitorResolution,
    );
    this.stats['nodejs.eventloop.delay.avg.ms'] = loopDelay;
    this.loopMonitor.reset();

    // Memory / Heap
    const memoryUsage = process.memoryUsage();
    this.stats['nodejs.memory.heap.allocated.bytes'] = memoryUsage.heapTotal;
    this.stats['nodejs.memory.heap.used.bytes'] = memoryUsage.heapUsed;

    this.stats['nodejs.memory.external.bytes'] = memoryUsage.external;
    this.stats['nodejs.memory.arrayBuffers.bytes'] =
      memoryUsage.arrayBuffers || 0; // Only available in NodeJS +13.0

    if (cb) process.nextTick(cb);
  }
}

module.exports = function createRuntimeMetrics(registry) {
  const collector = new RuntimeCollector();
  registry.registerCollector(collector);

  for (const metric of Object.keys(collector.stats)) {
    registry.getOrCreateGauge(metric, () => collector.stats[metric]);
  }
};