response-time middleware

Response time for Node.js servers.

This module creates a middleware that records the response time for requests in HTTP servers. The “response time” is defined here as the elapsed time from when a request enters this middleware to when the headers are written out to the client.

Installation

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install response-time

API

var responseTime = require('response-time');

responseTime([options])

Create a middleware that adds a X-Response-Time header to responses. If you don’t want to use this module to automatically set a header, please see the section about responseTime(fn).

Options

The responseTime function accepts an optional options object that may contain any of the following keys:

digits

The fixed number of digits to include in the output, which is always in milliseconds, defaults to 3 (ex: 2.300ms).

The name of the header to set, defaults to X-Response-Time.

suffix

Boolean to indicate if units of measurement suffix should be added to the output, defaults to true (ex: 2.300ms vs 2.300).

responseTime(fn)

Create a new middleware that records the response time of a request and makes this available to your own function fn. The fn argument will be invoked as fn(req, res, time), where time is a number in milliseconds.

Examples

express/connect

var express = require('express');
var responseTime = require('response-time');

var app = express();

app.use(responseTime());

app.get('/', function (req, res) {
  res.send('hello, world!');
});

vanilla http server

var finalhandler = require('finalhandler');
var http = require('http');
var responseTime = require('response-time');

// create "middleware"
var _responseTime = responseTime();

http.createServer(function (req, res) {
  var done = finalhandler(req, res);
  _responseTime(req, res, function (err) {
    if (err) return done(err);

    // respond to request
    res.setHeader('content-type', 'text/plain');
    res.end('hello, world!');
  });
});

response time metrics

var express = require('express');
var responseTime = require('response-time');
var StatsD = require('node-statsd');

var app = express();
var stats = new StatsD();

stats.socket.on('error', function (error) {
  console.error(error.stack);
});

app.use(
  responseTime(function (req, res, time) {
    var stat = (req.method + req.url).toLowerCase().replace(/[:.]/g, '').replace(/\//g, '_');
    stats.timing(stat, time);
  })
);

app.get('/', function (req, res) {
  res.send('hello, world!');
});

License

MIT