Listeners in Jmeter

Open-source software called Apache JMeter is generally employed for load, performance, and functional testing. It offers a range of features that enable programmers and testers to model various situations and gauge the effectiveness of their apps. JMeter's support for listeners is one of its important features. We will examine listeners in JMeter, their functionality, and their significance in performance testing in this article.

JMeter listeners operate by keeping an eye out for events produced by the test plan. These events may be associated with the beginning and completion of a test, the success or failure of a request, or the system under test's performance metrics. The listener records each event as it occurs and modifies its display accordingly.

Listeners in Jmeter

Listeners

Listeners are JMeter components that provide test plan results in a variety of formats, including graphs, tables, and trees. They offer in-the-moment updates on a test plan's performance, enabling developers and testers to keep an eye on how the system being tested is acting. In-built listeners offered by JMeter include those for Graph Results, Table Results, Summary Report, and View Results Tree.

JMeter's listeners are a potent tool that offer in-the-moment updates on a test plan's performance. Listeners can assist developers and testers in locating performance issues and optimising the system under test by keeping track of response times, error rates, and memory utilisation. Additionally, listeners can be used to produce reports that compile the outcomes of a test plan, enabling stakeholders to comprehend the system's performance. As a result, listeners are a crucial part of any strategy for performance testing.

Syntax

To add a listener, users can right-click on the test plan and select Add > Listener.

JMeter listeners are implemented as test plan components. Users can right-click on the test plan and choose Add > Listener to add a listener. Users can choose the kind of listener they want to add in a dialogue box that will be opened as a result. Users can modify the listener's properties and set it up to show test plan results after it has been added.

Algorithm

• Step 1 − The listener is included in the test plan and set up to present the intended outcomes.

• Step 2 − Requests are made of the system being tested while the test plan is being carried out.

• Step 3 − JMeter records and keeps in memory the responses to each request.

• Step 4 − The listener records the event and changes its display with the related results when an event is generated, such as the conclusion of a request or the conclusion of a test plan.

• Step 5 − The listener continues to capture and display results until the test plan is complete.

Approach

• Approach 1 − Monitoring Response Time

• Approach 2 − Analyzing Error Rates

• Approach 3 − Generating Reports

• Approach 4 − Identifying Memory Leaks

Approach 1: Monitoring Response Time

In this approach, we will see monitoring response time.Below is the path for the same in Jmeter GUI.

Example

Right-click on your test plan in the JMeter GUI and select Add -> Listener -> Response Times Over Time.
Select the HTTP request that you want to monitor from the left-hand panel.
Start your test and the Response Times Over Time graph will display the response time of each request over time.

Listeners offer a valuable means of tracking how rapidly the system undergoing testing reacts to inquiries. By leveraging this tool, developers and testers can pinpoint potential performance obstacles with greater ease and efficacy, allowing them to swiftly modify systems as required based on response times.

Approach 2: Analysing Error Rates

In this approach, we will see Analysing Error Rates.Below is the path for the same in Jmeter GUI.

Example

Right-click on your test plan in the JMeter GUI and select Add -> Listener -> Error % or Response Codes Per Second.
Start your test and the Error % or Response Codes Per Second graph will display the frequency of different response codes and the percentage of requests that resulted in an error.

Listeners can be used to monitor the error rates of requests made to the system being tested. The system can be improved by developers and testers by detecting faults and their root causes.

Approach 3: Generating Reports

In this approach, we will seeGenerating Reports.Below is the path for the same in Jmeter GUI.

Example

Right-click on your test plan in the JMeter GUI and select Add -> Listener -> Generate Summary Results or Generate Report Dashboard.
Configure the listener options as desired.
Start your test and the listener will generate a report that summarizes the results of your test plan.

Reports that list the outcomes of a test plan can be made using listeners. These reports can be used to inform stakeholders about the performance of the system being tested.

Approach 4: Identifying memory leaks

In this approach, we will see Identifying memory leaks.Below is the path for the same in Jmeter GUI.

Example

Right-click on your test plan in the JMeter GUI and select Add -> Listener -> Memory Usage or GC Activity.
Start your test and the listener will display the memory usage and garbage collection events during the test plan.
Analyze the results to identify potential memory leaks and address them before they become critical issues.

Memory leaks in the system being tested can be found using listeners. Developers and testers can find possible memory leaks and fix them before they become serious problems by looking at the memory use during the test plan.

JMeter listeners can be applied in many different ways to enhance the performance and dependability of applications. These are some of the most popular methods for employing listeners in JMeter

Conclusion

In conclusion, listeners are a crucial part of JMeter that aid in the interpretation of load testing results by testers. They offer a variety of graphical depictions, tables, and reports that make it easier to see how the tested system performed under various loads. The performance of the system can be improved by identifying performance bottlenecks, resource utilisation, response time, throughput, and other important metrics with the aid of listeners.It's crucial to remember that using too many listeners can compromise the effectiveness of the testing environment. Therefore, it is advised to only use the listeners required for the particular testing requirements.