metric middleware

metric.js

/**
 * Module dependencies
 */
var metric = require("metric-log");

module.exports = function() {
  // TODO what do we inherit from?
  var parent = metric.context();

  return function metricLogger(req, res, next) {
    req.metric = metric.context({
      request_id: req.get("Heroku-Request-ID")
    }).use(parent);
    
    next();
  }
};