circumambient-avg.js

var redis = require('redis').createClient();
var app = require('express')();

var total = 0, count = 0;

redis.on('message', function(channel, message) {
  if (channel == "requests") {
    var obj = JSON.parse(message);

    total += obj.duration;
    count += 1;
  }
});

app.get('/', function(req, res){
  if (count == 0) {
    res.send("No requests recorded");
  } else {
    res.send('Average: ' + Math.round(total / count / 1e3) + 'µs');
  }
});

process.on('SIGINT', function() {
  redis.end();
  process.exit();
});

redis.subscribe('requests');
console.log('started app.js on :4567');
app.listen(4567);