{"id":8295,"date":"2021-09-08T09:05:35","date_gmt":"2021-09-08T13:05:35","guid":{"rendered":"https:\/\/www.redline13.com\/blog\/?p=8295"},"modified":"2023-07-28T11:57:43","modified_gmt":"2023-07-28T15:57:43","slug":"troubleshoot-your-jmeter-load-tests","status":"publish","type":"post","link":"https:\/\/www.redline13.com\/blog\/2021\/09\/troubleshoot-your-jmeter-load-tests\/","title":{"rendered":"How to Troubleshoot your JMeter Load Tests"},"content":{"rendered":"

\"Troubleshoot<\/p>\n

An important part of developing a performance test involves debugging of the test itself. Simply put, we must \u201ctest our test\u201d to confirm that the results it generates are reliable. In this article we will walk you through how to troubleshoot your JMeter<\/a> load tests. We will include some specific ways that RedLine13 makes this process easier for cloud-based load testing.<\/p>\n

Common Mistakes<\/h3>\n

When creating a test plan, it is a good idea to be cognizant of common mistakes related to the design of the test.\u00a0 One of our industry partners The Test Tribe has a good article on Common mistakes in performance testing<\/a>.\u00a0 These include consideration of adequate ‘think time’, pitfalls of inaccurate workload modeling, and considerations of infrastructure monitoring.<\/p>\n

<\/a>Local Debugging<\/h3>\n

As the test plan is built up, we will invariably run in locally at various stages of construction. We will want to catch simple mistakes such as URL typos, logical errors, etc<\/em>., before we upload our test to the cloud with a service like RedLine13. While there are certainly additional methods and other tools available, we will describe a few common ways to debug your test plan locally.<\/p>\n

<\/a>View Results Tree<\/h3>\n

The easiest and most straightforward way to do this is to add a \u201cView Results Tree<\/em><\/a>\u201d listener to your JMeter test. Having this element added to your test plan will provide you with real time results from each request generated. It can be found under the \u201cListener<\/em>\u201d submenu when adding a new test plan element:<\/p>\n

\"Adding
Adding the “View Results Tree” listener to a JMeter test plan<\/figcaption><\/figure>\n

Here is some sample output for a very basic test plan. In this example, we can see that \u201cRequest B<\/em>\u201d is failing with a 500 Server Error<\/strong>:<\/p>\n

\"JMeter<\/p>\n

It is far better to catch errors due to simple typos or settings misconfiguration when running locally. Though we could find this information after running our test in the cloud \u2013 which we will discuss momentarily \u2013 it can save vast amounts of time catching these early.<\/p>\n

One thing we want to be careful of however, is that we remove any \u201cView Results Tree<\/em>\u201d listener before we run our test for any actual data collection. Having one of these listeners specified can have detrimental performance effects for actual test runs.<\/p>\n

<\/a>JMeter Log Viewer<\/h3>\n

Another good option for debugging tests locally is using JMeter\u2019s built-in \u201cLog Viewer<\/em><\/a>\u201d. This can be displayed from the JMeter GUI from the \u201cOptions<\/em>\u201d menu as shown below:<\/p>\n

\"The
The JMeter \u201cLog Viewer\u201d can be found under the \u201cOptions\u201d menu.<\/figcaption><\/figure>\n

In this example, we have captured an exception being thrown from a JSR223<\/a> post-processor<\/a>:<\/p>\n

\"Error
Error output within the JMeter logs<\/figcaption><\/figure>\n

Not only will the log viewer record error responses, but often we will be presented with detailed additional information which may be useful in identifying and resolving potential issues with our test plan.<\/p>\n

<\/a>API Debugging Tools<\/h3>\n

While the JMeter log output will provide some level of detail, there are times when we need additional visibility to the actual web response before an issue is obvious. Two common desktop tools for debugging web and API calls are Postman<\/a> and Telerik Fiddler<\/a>. Here is an example of an API call and actual resultant output using Postman:<\/p>\n

\"Example
Example of Postman testing an API<\/figcaption><\/figure>\n

In this case we can see not only the specific response, but also the raw output from the server. If the problem is not obvious to us at this point, a next step might be to search for this request within the application server logs of the target system we are testing.<\/p>\n

<\/a>Forensic Debugging in the Cloud<\/h3>\n

Once we run our load tests in the cloud, we no longer have the luxury of real-time monitoring of our load tests though the JMeter GUI. For performance testing it is in fact highly desirable to run JMeter \u201cheadless\u201d as to measure accurate performance characteristics of the system being tested. Having \u201cView Results Tree<\/em>\u201d elements or real-time log outputs would be detrimental to load generator performance and run counter to our testing goals.<\/p>\n

<\/a>The Error Table<\/em><\/h3>\n

RedLine13 provides several ways for you to investigate problems with your load test. The most visible of these is the \u201cError Table<\/em>\u201d which is displayed at the bottom of the results page for every test. It even provides some near-real time output of the most frequent errors while a test is running. Here is an example of a test that generated multiple errors:<\/p>\n

\"RedLine13<\/p>\n

These errors normally would show in the log viewer if we were debugging our test locally. The \u201cError Table<\/em>\u201d that we display on our results page is designed to be a convenient window into some common errors which may be occurring \u2013 however, it should not be depended upon for a complete listing of all<\/em> test errors.<\/p>\n

<\/a>Output Files<\/h3>\n

One of the best ways to debug a problematic load test is to directly view the JMeter log files. There is a feature built into RedLine13 that makes this task easy. In order to save your output and log files, you must check the \u201cSave Response Output and Calculate Percentiles<\/em>\u201d option prior to running your load test:<\/p>\n

\"Enabling<\/p>\n

This will provide you with the ability to download both JMeter output files as well as the raw log files for each load generator server. To download the files after the test completes, simply click on the compressed archive under \u201cOutput Files<\/em>\u201d for any listed load generator server:<\/p>\n

\"JMeter
JMeter output files and log files can be downloaded as a compressed archive.<\/figcaption><\/figure>\n

Within this compressed archive, you will find several files:<\/p>\n

\"Directory<\/p>\n

Under the \u201coutput<\/em>\u201d folder, there is a file named runLoadTest.log<\/strong> which will have the raw JMeter log output saved for your test. While this is often the most helpful file, the adjacent JTL file will contain useful response or failure information as well.<\/p>\n

Free RedLine13 Trial Subscription<\/h3>\n

Did you know that RedLine13 offers a fully featured free trial subscription? Sign up today<\/a> and discover the many benefits of load testing in the cloud with RedLine13.<\/p>\n","protected":false},"excerpt":{"rendered":"

An important part of developing a performance test involves debugging of the test itself. Simply put, we must \u201ctest our test\u201d to confirm that the results it generates are reliable. In this article we will walk you through how to troubleshoot your JMeter load tests. We will include some specific ways that RedLine13 makes this process easier for cloud-based load testing. Common Mistakes When creating a test plan, it is a good idea to be cognizantRead More →<\/a><\/p>\n","protected":false},"author":1,"featured_media":8306,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,7],"tags":[171,283,520],"class_list":{"0":"entry","1":"post","2":"publish","3":"author-user","4":"post-8295","6":"format-standard","7":"has-post-thumbnail","8":"category-blog","9":"category-jmeter","10":"post_tag-debugging","11":"post_tag-jmeter","12":"post_tag-troubleshooting"},"yoast_head":"\nHow to Troubleshoot your JMeter Load Tests - RedLine13<\/title>\n<meta name=\"description\" content=\"Here's how to troubleshoot your JMeter load tests. 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