JSR-233 Timer strange(?) behavior - jmeter

Question

I'm using JSR-223 Timer (jMeter 5.4.1), with groovy language, and trying to add delay\pauses to my threads.
I'm following the instructions by BlazeMeter (How to Easily Implement Pacing).
The strange(?) behavior is that the actual delay is double than required.
The script is as follows:
Long pacing = 5000 - prev.getTime();
Integer iPacing = pacing != null ? pacing.intValue() : null;
log.info("Transaction Pacing: " +String.valueOf(iPacing));
vars.put("myDelay", String.valueOf(iPacing));
return iPacing;
I get the duration of the Sampler action, then calculate "myDelay" as the difference from a base duration of 5,000 mSec. myDelay is a variable I use in the Flow Control Sampler.
Now the strange result:
The actual delay I achieve is TWICE than calculated. In this example, the delay is 5K mSec, but the actual delay is 10K mSec.
Now here is the real strange issue:
If I mark-out the return iPacing, the delay is 5K mSec as required (with a warning message in log file).
See the output below.
Why does the Flow Control Sampler adds myDelay and the iPacing values?
The first block - iPacing is returned. The overall pause is myDelay + iPacing.
The second block - iPacing is marked-out. The delay is myDelay only.

Answer 1

Your delay is TWICE simply BECAUSE you're setting it TWICE.
This statement:
return iPacing;
will create a delay BEFORE each SAMPLER in the JSR223 Time SCOPE
So there is no need to use the Flow Control Action sampler because you're creating the delay in the JSR223 timer ALREADY.
In general PACING is not implemented in JMETER because there is an EASIER way of creating the LOAD in terms of X REQUESTS per second: Constant THROUGHPUT timer and friends.