Jmeter: How to combine Constant Throughput Timer with ForEachController?

Question

I'm pretty new in the area of performance testing via Jmeter, and currently in my project I'm struggling with the following issue:

In my current project I have the following test plan (Jmeter 5.5):

• UDV - containing a list of ids (500 + ids)
• Main Thread group -- BeanShell Sampler (pulls a random id from the above list and attributes it to a thread) -- ForEach Controller (For each id in list) --- HTTP Request sampler (GET something/{$id}) ---- Constant Throughput Timer ---- Header Manager ---- Summary Report

The details I'm trying to use:

• Thread Number : 500
• Loop : infinite
• Duration: 10 mins (600 seconds)
• Desired Throughput = 500/sec

My questions here are:

• What am I doing wrong? I'm currently getting around 90/s Throughput

I ve tried to add a Precise Throughput timer, even tried removing the for each in order to have the http sampler alone, keep getting same result.

Answer 1

The throughput depends on your system under test response time.

You can reach 500 requests/sec with 500 users only if response time will be 1 second sharp (or less)

Constant Throughput Timer can only pause JMeter threads to limit the requests execution rate to the given value.

Try adding more threads and if the system under test supports the given load you should see throughput increase. Alternatively consider migrating to Concurrency Thread Group and Throughput Shaping Timer combination, they can be connected via Feedback Function and it will allow JMeter to kick off more threads if the current amount is not sufficient.

Also regarding using Beanshell - it's some form of a performance anti-pattern, since JMeter 3.1 you should be using JSR223 Test Elements with Groovy