JMeter, threads using dynamic incremented value - jmeter

Question

I have created a JMeter functional test that essentially:
creates a user;
logs in with the user;
deletes the user.
Now, I need to be able to thread this, and dynamically generate a username with a default prefix and a numerically incremented suffix (ie TestUser_1, TestUser_2, ... etc).
I used the counter, and things were working fine until I really punched up the number of threads/loops. When I did this, I was getting a conflict with the counter. Some threads were trying to read the counter, but the counter had already been incremented by another thread. This resulted in trying to delete a thread that was just created, then trying to log in with a thread that was just deleted.
The project is set up like this:
Test Plan
Thread group
Counter
User Defined Variables
Samplers
I was hoping to solve this problem by using the counter to append a number to the user defined variables upon thread execution, but the counter cannot be accessed in the user defined variables.
Any ideas on how I can solve this problem?
Thank you in advance.

Answer 1

I've used the following scheme successfully with any amount of test users:
1. Generate using beanshell-script (in BeanShell Sampler e.g.) csv-file with test-user details, for example:
testUserName001,testPwd001
testUserName002,testPwd002
. . .
testUserName00N,testPwd00N
with the amount of entries you need for the test-run.
This is done once per "N users test-run", in separate Thread Group, in setUp Thread Group or maybe even in separate jmx-script... makes no difference.
You can please find working beanshell-code below.
2. Create your test users IN TEST APPLICATION using previously created users-list.
If you don't need create in application you may skip this.
Thread Group
Number of Threads = 1
Loop Count = 1
. . .
While Controller
Condition = ${__javaScript("${newUserName}"!="",)} // this will repeat until EOF
CSV Data Set Config
Filename = ${__property(user.dir)}${__BeanShell(File.separator,)}${__P(users-list,)} // path to generated users-list
Variable Names = newUserName,newUserPwd // these are test-users details read from file into pointed variables
Delimiter = '
Recycle on EOF? = False
Stop thread on EOF? = True
Sharing Mode = Current thread group
[CREATE TEST USERS LOGIC HERE] // here are actions to create separate user in application
. . .
3. Perform multi-user logic.
Schema like the given above one but Thread Group executed not for 1 but for N threads.
Thread Group
Number of Threads = ${__P(usersCount,)} // set number of users you need to test
Ramp-Up Period = ${__P(rampUpPeriod,)}
Loop Count = X
. . .
While Controller
Condition = ${__javaScript("${newUserName}"!="",)} // this will repeat until EOF
CSV Data Set Config
Filename = ${__property(user.dir)}${__BeanShell(File.separator,)}${__P(users-list,)} // path to generated users-list
Variable Names = newUserName,newUserPwd // these are test-users details read from file into pointed variables
Delimiter = '
Recycle on EOF? = False
Stop thread on EOF? = True
Sharing Mode = Current thread group
[TEST LOGIC HERE] // here are test actions
. . .
The key idea is in using Thread Group + While Controller + CSV Data Set Config combination:
3.1. CSV Data Set Config reads details for each the test users from generated file:
. . . a. only once - because of "Stop thread on EOF? = True";
. . . b. doesn't block file for further access (in another thread groups, e.g., if there are any) - because of "Sharing Mode = Current thread group";
. . . c. pointed variables - "Variable Names = newUserName,newUserPwd" - you will use in further test-actions;
3.2. While Controller forces CSV Data Set Config to read all the entries from generated file - because of defined condition (until the EOF).
3.3. Thread Group will start all the threads with defined ramp-up - or simultaneously if ramp-up = 0.
You can take here template script for described schema: multiuser.jmx.
Beanshell script to generate test-users details looks like below and takes the following args:
- test-users count
- test-user name template ("TestUser_" in your case)
- test-user name format (e.g. 0 - to get TestUser_1, 00 - to get TestUser_01, 000- for TestUser_001, etc... you can simply hardcode this orexclude at all)
- name of generated file.
import java.text.*;
import java.io.*;
import java.util.*;
String [] params = Parameters.split(",");
int count = Integer.valueOf(params[0]);
String testName = params[1];
String nameFormat = params[2];
String usersList = params[3];
StringBuilder contents = new StringBuilder();
try {
DecimalFormat formatter = new DecimalFormat(nameFormat);
FileOutputStream fos = new FileOutputStream(System.getProperty("user.dir") + File.separator + usersList);
for (int i = 1; i <= count; i++) {
String s = formatter.format(i);
String testUser = testName + s;
contents.append(testUser).append(",").append(testUser);
if (i < count) {
contents.append("\n");
}
}
byte [] buffer = contents.toString().getBytes();
fos.write(buffer);
fos.close();
}
catch (Exception ex) {
IsSuccess = false;
log.error(ex.getMessage());
System.err.println(ex.getMessage());
}
catch (Throwable thex) {
System.err.println(thex.getMessage());
}
All together it will look like:
Sorry if answer is too overloaded.
Hope this helps.

Answer 2

The "User Defined Variables" config element does not pick up the reference variable from the "Counter" config element. I think this is a bug in JMeter. I have verified this behavior in version 3.2.
I added a "BeanShell Sampler" element to work around the issue.
Notice that the reference name of the "Counter" element is INDEX
The RUN_FOLDER variable gets set to a combination of the TESTS_FOLDER variable and the INDEX variable in the "BeanShell Sampler"
The "Debug Sampler" simply gathers a snapshot of the variables so I can see them in the "View Results Tree" listener element. Notice how the RUN_FOLDER variable has the INDEX variable value (5 in this case) appended.