This topic explains the meanings of key statistical metrics on each page in application monitoring of Application Real-Time Monitoring Service (ARMS).
Application Performance Index (APDEX) is an internationally accepted standard for evaluating application performance. According to APDEX, user experience of an application can be divided into three levels:
- - Satisfied (0 to T)
- - Tolerating (T to 4T)
- - Frustrated (greater than 4T)
The following formula is used to calculate the APDEX score:
APDEX score = (Satisfied samples + Tolerating samples/2)/Total samples
Image source: apdex.org
For ARMS, First Paint Time (FPT) is taken into account. The default value of T is 2s.
In ARMS, JS stability refers to the JS error rate of pages.
If any JS error occurs in a page view (PV) cycle, this PV cycle is an error sample.
Error rate = Error samples/Total samples
In addition to automatically reported JS errors, page exceptions include errors reported by manually calling methods in Methods user guide.
In ARMS, the page speed indicates the FPT of a page.
When performance or speed statistics are collected, all data is collected by the Navigation Timing API defined by the World Wide Web Consortium (W3C).
Image source: www.w3.orgField description
|dns||The time consumed for DNS resolution.||domainLookupEnd - domainLookupStart||None|
|tcp||The time consumed for TCP connection.||connectEnd - connectStart||None|
|ssl||The time consumed for SSL connection.||connectEnd - secureConnectionStart||This field is valid only when HTTPS is used.|
|ttfb||The time to first byte (TTFB), indicating the time consumed for a network request.||responseStart - requestStart||TTFB can be calculated in multiple ways. For TTFB calculation in ARMS, see Google development definition.|
|trans||The time consumed for data transmission.||responseEnd - responseStart||None|
|dom||The time consumed for document object model (DOM) resolution.||domInteractive - responseEnd||None|
|res||The time consumed for resource loading.||loadEventStart - domContentLoadedEventEnd||This field indicates the time consumed for synchronously loading resources on the page.|
|firstbyte||The time used for generating the first response packet.||responseStart - domainLookupStart||None|
|fpt||The FPT.||responseEnd - fetchStart||This field indicates the duration from the time when a request is initiated to the time when the browser starts to parse the bytes of the first batch of HTML documents.|
|tti||The Time to Interact (TTI).||domInteractive - fetchStart||After the browser resolves all HTML documents and constructs the DOM, the browser starts to load resources.|
|load||The time for completely loading the page.||loadEventStart - fetchStart||load = fpt + dom + (ready - tti) + res|
API call success rate
API call success rate = Successful API calling samples/Total samples
In addition to the automatically reported AJAX requests, samples for API call success rate statistics also include the data reported by manually calling methods in Methods user guide.