JMeter requests delayed without timer

Question

Within my JMeter test plan I have transaction controller which contains multiple requests inside. There are no any timers between HTTP samplers and controller is configured to generate parent sample.

When I run that test most of the samples are OK but there are couple outliers for which response times for parent sample are enormous though HTTP response times inside controller are quite low. After checking I found that there are couple minute gaps between HTTP requests even no timers are configured.

E.g. first HTTP sampler started 04:08:34 and load time was 358 ms. Second sampler started 04:11:41 - so it took more than 3 minutes to start it. Then there were couple more similar requests and overall parent sample time is more than 6 minutes though sum of all HTTP sampler load times is less than 1 second.

Does anyone has an idea why it occasionally takes very long to start next HTTP request? Can it be caused by low resources (like memory) on the machines from which test is executed (it's distributed testing)?

This can be due to the application that are you are testing, actually the application sometimes hold the request due to which all other delayed randomly. Can you share which type of requests you are generating? — Zohair
Actually I was wrong saying that there are no timers. There is a timer which is within a scope of all these requests. Seems the problem is that JMeter includes timer duration even transaction controller not configured to include duration of timer and pre-post processors. I suppose it's some bug in JMeter because thousands of samples are calculated correctly and just couple of them include timer duration. I use JMeter v5.1.1. Probably need to switch to some other version. — MantasG
Still the same with version 4.0. But it was working fine with version 2.13. I'm trying to migrate to later version but have this strange issue. — MantasG
I found that for these outliers some data is missing in results (JTL) file. I see just couple first HTTP samples from my Ultimate Thread Group in these cases. My group is configured to start next thread loop on error but in these cases I don't see any errors. Could it be a bug of Ultimate Thread Group? Could anyone recommend any alternatives for Ultimate Thread Group? — MantasG

Dmitri T Dmitri T · Accepted Answer · 2019-09-06T08:52:29

If you don't have Timers or Flow Control Action sampler or Inter-Thread Communication Plugin JMeter executes samplers as fast as it can immediately one after another.

The only reasons I can think of is are:

lack of resources (CPU, RAM, Network, Disk) on JMeter side, I would recommend ensuring that JMeter has enough headroom to operate using i.e. JMeter PerfMon Plugin
the delay can be caused by PreProcessors, PostProcessors and Assertions so you could take a thread dump - it will provide information where exactly JMeter "hangs"

JMeter requests delayed without timer

1 Answers