Json extract unique data - Jmeter - jmeter

Question

I am having a set of request in my Thread Group in which first request will feed inputs for the second request. I am using json extractor (match No.0) to extract the value from the list. I want to ensure that same data extracted in the Thread 1 is not been fetched in the subsequent thread runs. Can you please suggest how handle that.

Answer 1

As per JSON Extractor documentation
If the JSON Path query leads to many results, you can choose which one(s) to extract as Variables:
0 : means random (Default Value)
The "random" doesn't guarantee uniqueness so if you need the data to be unique - consider providing an incremented value to this "Match No" field.
Example setup:
Given the following JSON
{
"store": {
"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
},
"expensive": 10
}
Let's assume you want to use unique book title, i.e.
Sayings of the Century - for 1st iteration
Sword of Honour - for 2nd iteration
etc.
Amend "Match No" field value to look like:
${__intSum(${__jm__Thread Group__idx},1,)}
where __jm__Thread Group__idx is a pre-defined variable available since JMeter 4.0 which returns current Thread Group iteration and __intSum() is the JMeter Function which adds 1 to the iteration number (as it's zero-based)
the full JSON Extractor configuration would be something like:
That's basically it, now you have the confidence that the new value is being picked up for each Thread Group iteration, it can be checked using i.e. View Results Tree listener.