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node.js prometheus client basic metrics
Last updated: 10 months ago

Downloads: 7914

Reviews: 4

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Quick Start

Step1. Install Node.js Prometheus client and collect default metrics

npm install prom-client
import { collectDefaultMetrics } from 'prom-client';
collectDefaultMetrics({ timeout: 5000 });

https://github.com/siimon/prom-client

Step2 Expose your metrics endpoint and customize your metrics

Take koa2 (with pino logger) as example

import { yourRouter} from './routes';
import { collectDefaultMetrics, register, Counter, Gauge } from 'prom-client';
import Router = require('koa-router');

// tslint:disable-next-line: no-var-requires
const { startTime } = require('pino-http');

yourRouter.get('/metrics', (ctx) => {
  ctx.headers['content-type'] = register.contentType;
  ctx.body = register.metrics();
});

// Customized Http Metrics (Optional)
const httpMetricsLabelNames = ['method', 'path'];
const totalHttpRequestCount = new Counter({
  name: 'nodejs_http_total_count',
  help: 'total request number',
  labelNames: httpMetricsLabelNames
});
const totalHttpRequestDuration = new Gauge({
  name: 'nodejs_http_total_duration',
  help: 'the last duration or response time of last request',
  labelNames: httpMetricsLabelNames
});

function initMetrics4EachRoute(layer: Router.Layer) {
  layer.stack.unshift(async (ctx, next) => {
    await next();
    totalHttpRequestCount.labels(ctx.method, layer.path).inc();
    // start time symbol defined in pino-http
    totalHttpRequestDuration
      .labels(ctx.method, layer.path)
      .inc(new Date().valueOf() - (ctx.res as any)[startTime]);
  });
}

// call this function to intecept ALL routes with detailed HTTP metrics (Optional)
export function initRoutingMetrics() {
  yourRouter.stack.forEach(initMetrics4EachRoute);
}