Measured Node Metrics

Various metrics generators and http framework middlewares that can be used with a self reporting metrics registry to easily instrument metrics for a node app.

Install

npm install measured-node-metrics

What is in this package

Measured Node Metrics Module

See the docs for the main module to see the exported helper functions and maps of metric generators for various system and os metrics.

Example usage

const express = require('express');
const { createProcessMetrics, createOSMetrics, createExpressMiddleware } = require('measured-node-metrics');

const registry = new SelfReportingMetricsRegistry(new SomeReporterImple());

// Create and register default OS metrics
createOSMetrics(registry);
// Create and register default process metrics
createProcessMetrics(registry);
// Use the express middleware
const app = express();
app.use(createExpressMiddleware(registry));

// Implement the rest of app

You can also create your own middleware if your not using express, (please contribute it)

  const { onRequestStart, onRequestEnd } = require('measured-node-metrics');

  /**
   * Creates an Express middleware that reports a timer on request data.
   * With this middleware you will get requests counts and latency percentiles all filterable by status codes, http method, and uri paths.
   *
   * @param {SelfReportingMetricsRegistry} metricsRegistry
   * @param {number} [reportingIntervalInSeconds]
   * @return {Function}
   */
  createExpressMiddleware: (metricsRegistry, reportingIntervalInSeconds) => {
    return (req, res, next) => {
      const stopwatch = onRequestStart();

      req.on('end', () => {
        const { method } = req;
        const { statusCode } = res;
        // path variables should be stripped in order to avoid runaway time series creation, 
        // /v1/cars/:id should be one dimension rather than n, one for each id.
        const uri = req.route ? req.route.path : '_unknown';
        onRequestEnd(metricsRegistry, stopwatch, method, statusCode, uri, reportingIntervalInSeconds);
      });

      next();
    };
  }