Saving a max value of counter to file in JMeter - testing

Question

I'm using a SOAP/XML-RPC Request to test a WSDL. Additionally I created a Counter element for this request. Each call of one of the functions has to contain other value in one of parameters.
Is there any possibility to save the maximum counter value to the file?
So when I start test, the value will be loaded from the file and increase by the counter.
At the end, this max value will be again saved to this file. And so on, so on...

Answer 1

Let's drop the built-in Counter and pass around the thread safe AtomicInteger.
Add a setUp Thread Group with a JSR223 Sampler (choose groovy as a scripting language) to your test plan. We will use it to read the value from the file. This thread group will be executed before all other thread groups and will provide us with the initial value.
Add the following code to the sampler:
import java.util.concurrent.atomic.AtomicInteger
counter = new File($/C:\Path\ToFile\fileName.txt/$).text
ai = new AtomicInteger(Integer.valueOf(counter))
props.put("sharedAtomicInteger", ai)
Then add another JSR223 Sampler after SOAP/XML-RPC Request in your regular Thread Group.
Add the following code to the sampler:
ai = props.get("sharedAtomicInteger")
variable = ai.incrementAndGet()
vars.put("variable", Integer.toString(variable))
Now the value of the improvised counter is stored in a variable and can be used in other requests issued by this thread.
Add a tearDown Thread Group with a JSR223 Sampler to your test plan. This thread group will be executed after all other thread groups and will write the maximum value to the file.
Add the following code to the sampler:
ai = props.get("sharedAtomicInteger")
new File($/C:\Path\ToFile\fileName.txt/$).write(ai.toString())
Finally, your test plan should look like this:
setUp Thread Group
JSR223 Sampler
Regular Thread Group
SOAP/XML-RPC Request
JSR223 Sampler
tearDown Thread Group
JSR223 Sampler
P.S.
Bear in mind that for brevity's sake I used the put() method of java.util.Properties class which is discouraged in the documentation.

Answer 2

To save value into a file (assumes a JSR223 Element and Groovy language)
new File("value.txt").text = vars.get("foo")
To read the value from file (assumes __FileToString() function)
${__FileToString(value.txt,,)}

Answer 3

I used tips from the first comment and do it in the following way:
transfer - Simple Controller
reading transactionId - JSR223 PreProcessor
transfer - SOAPXML-RPC Request
saving transactionId - JSR223 PostProcessor
JSR223 PreProcessor
Script language: groovy
import java.util.concurrent.atomic.AtomicInteger;
initial = new File("${absolute_path}transactionid.txt").text;
initial = initial.trim();
ai = new AtomicInteger(Integer.valueOf(initial));
transactionId = ai.incrementAndGet();
vars.put("transactionId", Integer.toString(transactionId));
SOAPXML-RPC Request
Here I'm using transactionId as one of the parameters in the SOAP Request.
JSR223 PostProcessor
Script language: groovy
transactionId = vars.get("transactionId");
new File("${absolute_path}transactionid.txt").write(transactionId.toString());
${absolute_path} is a variable defined in test plan as:
${__BeanShell(import org.apache.jmeter.services.FileServer; FileServer.getFileServer().getBaseDir();)}${__BeanShell(File.separator,)}
It is a path to folder with this JMeter project. This folder also contains file which is read to this test case.