express-server-status-minus-git/index.js

Get a quick overview of the status of an express server (uptime, version, stats)

var path = require('path');
var os = require('os');
var fs = require('fs');
var moment = require('moment');
var requests = { total: 0 };
var requests_per_minute = [];

for(var i=0;i<60;i++)
  requests_per_minute[i] = 0;

var uptime_start = new Date();
var exec = require('child_process').exec;

var sum = function(arr, from, length) {
  var total = 0;
  for(var i=from-length;i<from;i++) {
    total += arr[(i+arr.length)%arr.length];
  }
  return total;
}

var average = function(arr, from, length) {
  var total = sum(arr, from, length   );
  return Math.round(total/arr.length);
}

var resetCounter = function() {
  var minute = (new Date).getMinutes();
  requests_per_minute[(minute+1)%59] = 0;
}
// Every minute, we reset the oldest entry
setInterval(resetCounter, 60*1000);

module.exports = function(app, options) {

  var server = { status: "up" };

  var filepath = "package.json";
  var i = 0;
  do {
    filepath = require.main.paths[i++].replace(/\/[^\/]*$/,'/') + "package.json";
  }
  while(!fs.existsSync(filepath) && i < require.main.paths.length);

  try {
    var pkg = require(filepath);
    server.name = pkg.name;
    server.version = pkg.version;
  } catch(e) { console.error("express-server-status> Error loading " + filepath, e); }

  app.get('*', function(req, res, next) {
    requests.total++;
    var minute = (new Date).getMinutes();
    requests_per_minute[minute]++;
    return next();
  });

  return function(req, res, next) {

    req.stats = {}
    req.stats.start = new Date;

    // decorate response#end method from express
    var end = res.end;
    res.end = function () {
      req.stats.responseTime = (new Date) - req.stats.start;
      // call to original express#res.end()
      res.setHeader('X-Response-Time', req.stats.responseTime);
      end.apply(res, arguments);
    }

    var minute = (new Date).getMinutes();
    server.started_at = moment(uptime_start);
    server.uptime = Math.round((new Date() - uptime_start) / 1000);
    server.uptime_human = moment(uptime_start).fromNow();
    server.env = process.env.NODE_ENV;

    var node = {
      version: process.version,
      memoryUsage: Math.round(process.memoryUsage().rss / 1024 / 1024) + 'M',
      uptime: process.uptime()
    };
    var system = {
      loadavg: os.loadavg(),
      freeMemory: Math.round(os.freemem() / 1024 / 1024) + 'M',
      hostname: os.hostname()
    };

    // requests.per_minute = requests_per_minute;
    requests.last_minute = sum(requests_per_minute, minute, 1);
    requests.last_5mn_avg = sum(requests_per_minute, minute, 5);
    requests.last_15mn_avg = average(requests_per_minute, 0, 15);
    server.requests = requests;
    const status = { server: server, node: node, system: system };

    res.send(status);

  };

}