JMeter is a performance analysis and measurement tool for several software products and services. This is solely a Java-free program for testing FTP or Web applications. It's used to run Web application performance tests, load testing, and functional tests. This blog looks at a crucial JMeter concept called JMeter Correlation.
Correlation is the process of obtaining information from one request that can be used in a future request or any other request that has to be completed. Processors are required for extracting values from a request. HTMLLinkParser and other pre-processors can remove all links from a page received in response.
In most cases, post-processors such as XPath and Regular Expression Extractor extract values from responses and store them in variables. The same variable can now be used in the following request and future submissions. In most circumstances, you'll find JMeter obtaining session, cooked, login credentials and then using them as a parameter in other proposals.
Correlation is the process of transferring information from one step's response to another step's request. It catches and saves the server's dynamic answer before passing it on to other requests. When a reply returns different data for each iterating request, it is active. This might sometimes affect subsequent queries. Correlation is necessary for performance load test scripting because it will become ineffective if it is not handled correctly.
One of the most fundamental components of scripting is a correlation. It retrieves dynamic data from previous requests and posts it to new submissions. Let's look at an example to see why we require correlation in the first place. Assume we've captured a scenario in which:
Session variables are produced dynamically when we log in to a website. These session variables are passed along to subsequent requests, assisting in validating and verifying the actions taken. Otherwise, the test will fail because the web requests do not match the dynamic variables. We'll need to employ the Regular Expression Extractor for correlation.
When utilizing JMeter's Regular Expression Extractor, four stages follow. It contains the following items: When utilizing JMeter's Regular Expression Extractor, four steps follow. It includes the following items:
The JMeter program must first be downloaded and installed on your PC.
The technique of recording and storing the server's dynamic response and passing it on to subsequent queries is known as correlation. When a reply might return different data for each iterating request, it is termed active, sometimes affecting the following questions. Correlation is a crucial step in performance load test scripting since if it isn't done correctly, our script will be rendered useless.
It is vital to determine which reaction is dynamic and static from testing (the data stays the same for iterating requests). Every HTTP web performance test typically includes data correlation. The correlation may be ignored when evaluating static content pages, such as some homepages and contacts. In other circumstances, correlation handling is unavoidable at some point throughout the test.
The developer manually detects correlation points in the test flow and maps the values to be substituted in subsequent requests, known as manual correlation.
In Apache JMeterTM, correlation is handled in two steps:
A "Regular Expression Extractor" may be seen in the image above, which extracts data from the preceding sample's body. The variable $data-cmsid, which will be dynamically mapped during execution, can be used in subsequent requests after this component. This blog post will teach you how to correlate manually.
For the desktop version, JMeter does not include a native autocorrelation function. However, for free, we can use the BlazeMeter SmartJMX, which is included in the BlazeMeter Proxy Recorder. According to the saved script, the recorder has generated a JMX script that is automatically correlated.
When a script requires many different users, parameterization is utilized. CSV files can be used to retrieve other users and data. So, if a script runs with a thread count of 50, it will download a new user detail from the CSV file each time it runs. To Deal With Correlation The post-processor "Regular expression extractor" extracts the variable’s value from the first request for subsequent requests. Parameterization is concerned with the user's input values, whereas Correlation is examined with the data given by the server in response to the request made.
To work with JMeter dynamic values, you must first receive and save the dynamic value from the response and then utilize that value in subsequent requests. The Regular expression extractor post-processor is used to do this.
The "Regular expression extractor" post-processor is necessary to correlate header information in JMeter.
JMeter's correlation is a crucial feature. We learned about JMeter Correlation and the many sorts of correlations in this blog, like Manual JMeter Correlation and JMeter Auto-Correlation. We hope you found this information to be beneficial.
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