Deprecate User Defined Variables, and hide it from the menus

[vlsi]

Expected behavior

There should be a way to initialize variables at the beginning of the test.
For instance:
a) Initialize variables based on properties
b) Set thread-group specific variables

In JMeter, variable should have thread scope, and it is unexpected for the variables from different threads to interfere.
The name User Defined Variable suggests that the config element configures variables, however, it configures test plan variables which is completely misleading

Actual behavior

Currently, User Defined Variables are replaced globally in the test plan which results in surprising behaviour. For instance, if several User Defined Variables located under different thread groups share a variable name, only one of the values win, and the same value is reused for all the threads.

See also

• Make setting variables predictable #4360

Steps to reproduce the problem

udv_sharing.zip

JMeter Version

5.5

Java Version

17

OS Version

No response

[markuswege]

The behaviour of the User Defined Variables is documented:
https://jmeter.apache.org/usermanual/component_reference.html#User_Defined_Variables

UDV are initialized once at test start.

To make this behaviour more clear and to prevent errors, UDVs should be only allowed on "root" level. More than one UDV block could make sense in case some variables rely on others being set before.

[vlsi]

Frankly speaking, that documentation and the behavior were obscure to me until I analyzed the sources.
At the same time, the reasons for that behavior are not clear either.

[markuswege]

I would suggest not to deprecate the UDV, but to separate these.
Global UDV and thread scoped UDV.
That way, the scopes of both would be clear whilst remaining backward compatible.