How to add unique to each request in JMeter - jmeter

Question

I'm having a JSON array with n number of elements like productName, productId. I would like to generate unique id in productId for each element and for each request.
Currently, I'm reading productId from .csv file but for each request same productId is applied for all the elements. For example:
test.csv
productId
10
11
12
13
14
In JMeter it substitute like below for request 1:
[
{
"productName": "Apple",
"productId": "10"
},
{
"productName": "Apple",
"productId": "10"
},
{
"productName": "Apple",
"productId": "10"
},
{
"productName": "Apple",
"productId": "10"
}
]
request 2:
[
{
"productName": "Apple",
"productId": "11"
},
{
"productName": "Apple",
"productId": "11"
},
{
"productName": "Apple",
"productId": "11"
},
{
"productName": "Apple",
"productId": "11"
}
]
But the way I'm expecting is, first request should be
[
{
"productName": "Apple",
"productId": "10"
},
{
"productName": "Apple",
"productId": "11"
},
{
"productName": "Apple",
"productId": "12"
},
{
"productName": "Apple",
"productId": "13"
}
]
And second request should be like below and so on,
[
{
"productName": "Apple",
"productId": "14"
},
{
"productName": "Apple",
"productId": "15"
},
{
"productName": "Apple",
"productId": "16"
},
{
"productName": "Apple",
"productId": "17"
}
]
productId should generate with some random id for each request and apply random id for all the elements in the json. How can we achieve this in JMeter?

Answer 1

You can generate a random unique number with JMeter function __UUID
Replace the productId with the following
${__UUID}
Example
[
{
"productName": "Apple",
"productId": "${__UUID}"
},
{
"productName": "Apple",
"productId": "${__UUID}"
},
{
"productName": "Apple",
"productId": "${__UUID}"
},
{
"productName": "Apple",
"productId": "${__UUID}"
}
]

Answer 2

As per CSV Data Set Config documentation:
By default, the file is only opened once, and each thread will use a different line from the file. However the order in which lines are passed to threads depends on the order in which they execute, which may vary between iterations. Lines are read at the start of each test iteration. The file name and mode are resolved in the first iteration.
If you want to generate a random number you can just go for __Random() function which produces a random number within the given range:
[
{
"productName": "Apple",
"productId": "${__Random(1,2147483647,)}"
},
{
"productName": "Apple",
"productId": "${__Random(1,2147483647,)}"
},
{
"productName": "Apple",
"productId": "${__Random(1,2147483647,)}"
},
{
"productName": "Apple",
"productId": "${__Random(1,2147483647,)}"
}
]
More information on JMeter Functions concept: Apache JMeter Functions - An Introduction

Answer 3

Another solution could be using the __CSVRead function instead of CSV Data Set Config element.
Note :
You will have to remove the column names. i.e. First row
Ensure you have sufficient test data in the CSV file
[
{
"productName": "Apple",
"productId": "${__CSVRead(productIds.csv,0)}${__CSVRead(productIds.csv,next)}"
},
{
"productName": "Apple",
"productId": "${__CSVRead(productIds.csv,0)}${__CSVRead(productIds.csv,next)}"
},
{
"productName": "Apple",
"productId": "${__CSVRead(productIds.csv,0)}${__CSVRead(productIds.csv,next)}"
},
{
"productName": "Apple",
"productId": "${__CSVRead(productIds.csv,0)}${__CSVRead(productIds.csv,next)}"
}
]