Monitor

The @esmj/monitor is module for collecting node metrics from native node API.

Requirements

• Node 18+

Install

npm install @esmj/monitor

Usage

It works for both Javascript modules (ESM and CJS).

// server.js
import { createMonitoring } from '@esmj/monitor';

const { monitor, metricsHistory } = new createMonitoring();

const { unsubscribe } = monitor.subscribe((metric) => {
  console.log(metric);
//   {
//   cpuUsage: { user: 1692, system: 925, percent: 0.26 },
//   eventLoopDelay: {
//     min: 20.07,
//     max: 21.15,
//     mean: 20.78,
//     stddev: 0.38,
//     percentile80: 21.08
//   },
//   eventLoopUtilization: {
//     idle: 992.72,
//     active: 7.85,
//     utilization: 0.01
//   },
//   loadAverage: {
//     minute1: 3.38,
//     minute5: 8.28,
//     minute15: 9.15
//   },
//   memoryUsage: {
//     percent: 5.23,
//     rss: 54.2,
//     heapTotal: 20.2,
//     heapUsed: 17.74,
//     external: 0.9,
//     arrayBuffers: 0.07
//   },
//   gc: { entry: null },
//   process: {
//     pid: 53509,
//     ppid: 53480,
//     platform: 'darwin',
//     uptime: 14.656514084,
//     version: 'v18.12.1'
//   }
// }
});

monitor.start();

setTimeout(() => {
  console.log(metricsHistory.percentile('cpuUsage.percent', 80)); // 1 
  console.log(metricsHistory.percentile('memoryUsage.rss', 80)); // 61
  console.log(metricsHistory.trend('memoryUsage.rss').predict()); // 65
}, 5000);

setTimeout(() => {
  console.log(metricsHistory.size) // 15;
  console.log(metricsHistory.current) // return last captured metric structure
  unsubscribe();
  monitor.stop();
  console.log(metricsHistory.percentile('cpuUsage.percent', 80)); // undefined 
  console.log(metricsHistory.percentile('memoryUsage.rss', 80)); // undefined
}, 15000);

API

monitor = new Monitor(options?)

Create a new instance of Monitor.

options?

Type: object

Configure options for the new instance of Monitor.

options.interval?

Type: integer Default: 1000

Measure interval metric.

start()

Monitoring start measure node metric.

stop()

Monitoring stop measure node metric.

subscribe(listener)

Subscribe listener for metrics.

Returns a subscription object with unsubscribe method.

unsubscribe(listener)

Remove subscription.

add(metric)

Monitoring add measure new metric.

metric

Type: Metric

Add new metric to monitoring.

remove(metric)

Remove defined metric from monitoring.

metricsHistory = new MetricsHistory(options.metricsHistory?)

Create a new instance of Monitor.

options?

Type: object

Configure options for the new instance of MetricsHistory.

options.limit?

Type: integer Default: 60

FIFO size of array for calculating percentile and linear regressions.

percentile(key, number)

Returns defined percentile for measured metric

key

Type: String

Path in measured metric structure.

number

Type: Number

Percentile number for FIFO array

percentileMemo(key, number)

Memoized version of percentile function. Cache is cleared after capture new metric.

trend(key, limit)

Returns linear regression variables slope, yIntercept and predict function for measured metric.

key

Type: String

Path in measured metric structure.

limit

Type: Number

Defined how much records use for calculating linear regression. Default is use all records from FIFO array.

trendMemo(key, number)

Memoized version of trend function. Cache is cleared after capture new metric.