Parallel execution of Samplers in JMeter with different URL parameters - jmeter

Question

There is "ForEach" controller in JMeter which takes an array of items and executes a sampler with each item. This is very useful when you need to execute a sampler with different parameters based on data received in previous request. However, "ForEach" controller runs samplers one after the other.
What I am looking for is, execute the samples in parallel. There is a plug in available in JMeter called, "bzm - Parallel Controller". However, this doesn't accept any input variable like "ForEach" controller does.
For example, I have following data in database. Author along with their books.
[
{
"firstName": "William",
"lastName":"Shakespeare",
"Title": "Mr",
"id": "1",
"books": [
{
"id": "WS1",
"title": "King John",
"year":"1596"
},
{
"id": "WS2",
"title": "Julius Caesar",
"year": "1599"
},
{
"id": "WS3",
"title": "Romeo and Juliet",
"year": "1595"
}
],
"Nationality": "English"
},
{
"firstName": "Sidney",
"lastName":"Sheldon",
"Title": "Mr",
"id": "2",
"books": [
{
"id": "SS1",
"title": "The Naked Face",
"year":"1969"
},
{
"id": "SS2",
"title": "A Stranger in the Mirror",
"year": "1976"
},
{
"id": "SS3",
"title": "Bloodline",
"year": "1977"
}
],
"Nationality": "American"
},
{
"firstName": "Eiichiro",
"lastName":"Oda",
"Title": "Mr",
"id": "3",
"books": [
{
"id": "EO1",
"title": "Wanted",
"year":"1992"
},
{
"id": "EO2",
"title": "Ikki Yako",
"year": "1993"
},
{
"id": "EO3",
"title": "Monsters",
"year": "1994"
}
],
"Nationality": "Japanese"
}
]
In my JMeter Test plan, I have defined a CSV Data Set Config file to store the ids of all authors in my system.
And then, there is a Thread Group. Inside thread group, I have a HTTP Sampler, GET /authors/{id}/books. for Example GET /authors/1/books. This will get all the books written by author "William Shakespeare".
Using JSON Extractor, I can capture the array of book ids returned by GET /authors/{id}/books.
There are 3 books with ids WS1, WS2 and WS3. Now for each of the books, I need to run another HTTP Sampler
PUT /books/WS1
PUT /books/WS2
PUT /books/WS3.
When I use ForEach controller, I can specify the input variable which was captured from previous JSON extractor. And it loops through each PUT request, for each book id. I want to do the same, but in PARALLEL, not sequential.
Does anyone know how to achieve this? or we have to write custom groovy/BeanShell script for this? If custom Groovy/BeanShell script is the only way, can you please tell me how to write this
Many thanks

Answer 1

You can do that by placing each test in a separate threadGroup.
You have a flag in the main test plan that controls if threads are executed in parallel or consecutively.

Answer 2

You're using not very correct test element, consider switching to Parallel Sampler instead.
Given you have the following JMeter Variables:
book_1=WS1
book_2=WS2
book_3=WS3
book_matchNr=3
You can add a Parallel Sampler and configure it to hit URLs containing ${book_1}, ${book_2} and ${book_3}
All the URLs to Retrieve will be executed in parallel:
More information: How to Use the Parallel Controller in JMeter

Answer 3

You could dynamically add URLs to Parallel HTTP Requests sampler.
Add JSR223 PreProcessor like a child to Parallel HTTP Requests sampler.
To script area add something like that:
String url = "https://examle.url.com/?book=";
1.upto(vars.get('book_matchNr') as int, {
index -> {
sampler.addURL(url + vars.get('book_' + index))
}
});