Action X, XHR total
Can you please explain how 509.00 ms was arrived at with respect to the below waterfall?
This means that after 6620ms this XHR call was executed which took a total of 509ms. The Elapsed Time tells you when this node was started in relation to the Entry Point Node (Elapsed Time=0)
I would assume your page got loaded and then some javascript sent that request. later one you see more AJAX Requests. One after 14.3s, the next after 18.5, then after 25.2. Maybe a background polling XHR call?
Andi - I am thinking that this 509 should be arrived from 174.09 + ?
It means that the response time of that XHR Request in the browser took 509ms - we capture that time through our JavaScript agent by measuring the time from send until the response is back in the browser. On the web server itself this request only took 174.
The difference can be explained by different technical issues:
a) time spent on the network
b) time spent in the browsers network layer, e.g: not enough physical connections available to that domain - therefore the XHR rquest had "to wait" for an available connection -> that often happens if you have overloaded pages which lets you run into the browser connection limits per domain
Hope this makes sense
