How New Relic measures page load timing

The web application time includes the time spent on the application server. This can only be determined if the browser instrumentation for page load timing was provided by an APM agent.

The Network layer includes time spent in redirects as well as in requesting and receiving HTML. It does not include time on the server or for static assets.

Network time measurement starts from the initial click on a link. Network time includes DNS and may include more than one lookup if you have redirects on your site, TCP (including the firewall, unless you have configured request queue time monitoring), and SSL connect time.

• If you have configured request queue time monitoring, then the network time does not include any of the request queue time that occurs after the X-Request header.

• If you have not configured request queue time monitoring, then the network time does include all of the request queue time.

  The Navigation Timing Specification API provides a detailed breakdown of network time. (For old browsers, the timer starts on the "before unload event.")

  For apps that have been deployed using the copy/paste method, Browser includes web app and queue time in Network time. This is because browser relies on the server-side agent to pass the application values to the browser agent through auto-injection.

  For more information about how this backend time breaks down from the browser's point of view, use the Session traces page. The session traces report on all the network related events available, so you can see on a case-by-case basis how the browser is spending time on DNS lookups and other network events.

  Importante

  Even with request queuing configured, the frontend server's setup can still affect network time. This is because the frontend server does not add the queueing time header until after it actually accepts and processes the request. If the frontend server is configured in some way that causes requests to start backlogging and to queue up in the listener socket that the frontend server uses to accept connections, then you will see network time increase for browser monitoring. The queueing time headers can never account for backlog in this listener socket.

DOM processing is the time it takes to parse the HTML into a DOM and retrieve or execute synchronous scripts. If the browser starts to download images in this phase, page load timing will capture the image load time.

The DOM processing and page rendering layers include network time for static assets (assets that are not explicitly retrieved after page load). However, if a script on the page dynamically inserts image tags and loads images after the server or content delivery system (CDN) finishes, page load timing cannot capture the image load time.

The Page rendering phase is the time between the DOM being complete and the window load event. This phase measures browser-side processing of the page content, and often includes time for scripts and static assets to load.

Request queuing will be displayed in the load time chart if that account has browser monitoring and APM linked. In New Relic, request queuing refers to the time between a request entering your production systems and it reaching your application. Depending on the specifics of your production infrastructure, this time may include an actual queue that requests enter, or it may represent other functions that take time (such as load balancing or internal network latency).