JMeter - Run a python script before calling each HTTP request sampler

Question

I am new to Jmeter. My HTTP request sampler call looks like this

Path= /image/**image_id**/list/
Header =  "Key" : "Key_Value"

Key value is generated by calling a python script which uses the image_id to generate a unique key.

Before each sampler I wanted to generate the key using python script which will be passed as a header to the next HTTP Request sampler.

I know I have to used some kind of preprocessor to do that. Can anyone help me do it using a preprocessor in jmeter.

A simpler approach I tend to use is to run use the script beforehand to create a file with parameters that is read via the JMeter CSV handler resulting in a `${imgid}` variable in your sampler URL. — rsp, Jul 24 '14 at 10:44

score 5 · Answer 1 · answered Jul 01 '14 at 15:22

5

I believe that Beanshell PreProcessor is what you're looking for.

Example Beanshell code will look as follows:

import java.io.BufferedReader;
import java.io.InputStreamReader;

Runtime r = Runtime.getRuntime();
Process p = r.exec("/usr/bin/python /path/to/your/script.py");
p.waitFor();
BufferedReader b = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
StringBuilder response = new StringBuilder();
while ((line = b.readLine()) != null) {
    response.append(line);

}

b.close();
vars.put("ID",response.toString());

The code above will execute Python script and put it's response into ID variable.

You will be able to refer it in your HTTP Request as /image/${ID}/list/

See How to use BeanShell: JMeter's favorite built-in component guide for more information on Beanshell scripting in Apache JMeter and a kind of Beanshell cookbook.

You can also put your request under Transaction Controller to exclude PreProcessor execution time from load report.

answered Jul 01 '14 at 15:22

Dmitri T

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Thanks a lot for your help. Can you also let me know how to pass parameter to this python file – user1788294 Jul 01 '14 at 15:56
You can just add arguments after script like `/usr/bin/python /path/to/your/script.py param1 param2` – Dmitri T Jul 01 '14 at 15:58
I am passing parameter like this it is not working String s ="param" /usr/bin/python /path/to/your/script.py s . In python script it is printed as "s" and not "param" – user1788294 Jul 01 '14 at 16:20
`String s = "param"; Process p = r.exec("/usr/bin/python /path/to/your/script.py " + s);` - this way it should work – Dmitri T Jul 02 '14 at 14:21
1

If you're going to fork a process, why wouldn't you use the OS Process Sampler? – Alastair McCormack May 08 '15 at 11:21

Dominik Antal · Answer 2 · 2014-07-01T14:35:02.063

3

A possible solution posted by Eugene Kazakov here:

JSR223 sampler has good possibility to write and execute some code, just put jython.jar into /lib directory, choose in "Language" pop-up menu jython and write your code in this sampler.

Sadly there is a bug in Jython, but there are some suggestion on the page.

More here.

edited Jul 01 '14 at 14:35

answered Jul 01 '14 at 14:20

Dominik Antal

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i would not recomand jython library as its very bugy, it worked fine for me with low number of threads, but when running a load test with many threads it just kept getting deadlocks and crashed my tests – omriman12 Jun 11 '22 at 04:04

score 2 · Answer 3 · answered Jan 07 '16 at 11:55

You can use a BSF PreProcessor.

First download the Jython Library and save to your jmeter's lib directory.

On your HTTP sampler add a BSF PreProcessor, choose as language Jython and perform your needed magic to obtain the id, as an example I used this one:

import random
randImageString = ""
for i in range(16):
    randImageString = randImageString + chr(random.randint(ord('A'),ord('Z')))

vars.put("randimage", randImageString)

Note the vars.put("randimage",randImageString") which will insert the variable available later to jmeter.

Now on your test you can use ${randimage} when you need it:

Now every Request will be different changing with the value put to randimage on the Python Script.

i would not recomand jython library as its very bugy, it worked fine for me with low number of threads, but when running a load test with many threads it just kept getting deadlocks and crashed my tests — omriman12, Jun 11 '22 at 04:04

JMeter - Run a python script before calling each HTTP request sampler

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