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I'm doing load testing using JMeter, and on some endpoint trigged when a user clicks on a button to submit a form, the load time equals latency. I'm wondering why?

S_H
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1 Answers1

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As per JMeter glossary:

Latency. JMeter measures the latency from just before sending the request to just after the first response has been received. Thus the time includes all the processing needed to assemble the request as well as assembling the first part of the response, which in general will be longer than one byte. Protocol analysers (such as Wireshark) measure the time when bytes are actually sent/received over the interface. The JMeter time should be closer to that which is experienced by a browser or other application client.

So another term for the "latency" is time-to-first-byte

Again looking into the aforementioned glossary:

Elapsed time. JMeter measures the elapsed time from just before sending the request to just after the last response has been received. JMeter does not include the time needed to render the response, nor does JMeter process any client code, for example Javascript.

So another term for the "elapsed time" is time-to-last-byte

So delta between the elapsed time and the latency is the time for the all response to travel between application under test back to JMeter and if the response is small enough and the connection is fast enough it might be the case the whole response can be received in the same millisecond.

Another possible reason is that the response is cached so no actual request is being made, just little fast lightweight HEAD request to check whether it is needed to re-request the body data

Dmitri T
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  • Thank you so much for replying to my question; it indeed helped me. Another question I'm asking myself is: I know that JMeter does not work as the browser(it does not execute javascript), but the fact that a website is a Single page application developed using Angular and some section of that site (including the section of the button I mentioned above) can be updated without changing the URL and without reloading the entire page, can't this also be the cause the load time be small? – S_H Jan 10 '21 at 18:49