phantomas/modules/keepAlive/keepAlive.js

Headless Chromium-based web performance metrics collector and monitoring tool

/**
 * Analyzes if HTTP responses keep the connections alive.
 */
"use strict";

module.exports = function (phantomas) {
  var closedConnectionHosts = {};

  phantomas.setMetric("closedConnections"); // @desc number of requests not keeping the connection alive and slowing down the next request

  phantomas.on("recv", (entry) => {
    var connectionHeader = (entry.headers.Connection || "").toLowerCase(),
      // Taking the protocol in account, in case the same domain is called with two different protocols.
      host = entry.protocol + "://" + entry.domain;

    if (connectionHeader.indexOf("close") !== -1) {
      // Don't blame it immediatly, wait to see if the connection is needed a second time.
      closedConnectionHosts[host] = entry.url;
    }
  });

  phantomas.on("send", (entry) => {
    var host = entry.protocol + "://" + entry.domain,
      previousClosedConnection = closedConnectionHosts[host];

    if (typeof previousClosedConnection !== "undefined") {
      // There was a closed connection. We can blame it safely now!
      phantomas.incrMetric("closedConnections");
      phantomas.addOffender("closedConnections", previousClosedConnection);

      phantomas.log(
        "keepAlive: connection for <%s> was closed, but the page requested <%s>",
        host,
        entry.url
      );

      closedConnectionHosts[host] = undefined;
    }
  });
};