Breakdown metrics

Breakdown metrics help you visualize where your application is spending the majority of its time — allowing you to find the root cause of performance problems even quicker. These metrics are calculated for each transaction based on its corresponding types.

Page load transactions breakdown aligns closely with the processsing model of the Navigation Timing API available in the browser. The different types of metrics are:

• DNS - Duration of the DNS query for the current page (domainLookupEnd - domainLookupStart).
• TCP - How long it took to establish the TCP connection to the server. Includes the TLS negotitaion time for HTTPS pages (connectEnd - connectStart).
• Request - The time elapsed between the browser making the HTTP request and receiving the first byte of the response (responseStart - requestStart). Also referred as TTFB (Time to First Byte).
• Response - The elapsed time between the first and the last byte of the response. Referred commonly as Content Download time (responseEnd - responseStart).
• Processing - Time taken to render the current page; this includes downloading necessary resources like JavaScript, Images, CSS, etc. required by the page (domComplete - domLoading).
• Load - Duration of the load event after the browser is done dowloading the document and resources required for rendering the page (loadEventEnd - loadEventStart). Duration would be longer if there are multiple listeners for the load event.

For other transactions including SPA (Single Page Application) navigations and user created ones, the breakdown metrics are calculated based on the spans associated with the transaction.

• If a SPA navigation transaction (route-change) spends 20% of the time downloading resources and 80% of the time waiting for the API call response, then the transaction breakdown would indicate time spent by span type as resource - 20% and http - 80%.
• For a transaction that has concurrent async spans, the breakdown would include the sum of time spent by each span type.