Troubleshoot load test errors by downloading Apache JMeter logs

Learn how to diagnose and troubleshoot errors while running a load test with Azure Load Testing. Download the Apache JMeter worker logs or load test results for detailed logging information.

When you start a load test, the Azure Load Testing test engines run your Apache JMeter script. Errors can occur at different levels. For example, during the execution of the JMeter script, while connecting to the application endpoint, or in the test engine instance.

You can use different sources of information to diagnose these errors:

There might also be problems with the application endpoint itself. If you host the application on Azure, you can configure server-side monitoring to get detailed insights about the application components.

Load test error indicators

After running a load test, there are multiple error indicators available:

  • The test run Status information is Failed.

    Screenshot that shows the load test dashboard, highlighting status information for a failed test.

  • The test run statistics shows a non-zero Error percentage value.

  • The Errors graph in the client-side metrics shows errors.

    Screenshot that shows the load test dashboard, highlighting the error information.


  • An Azure account with an active subscription. If you don't have an Azure subscription, create a free account before you begin.
  • An Azure load testing resource that has a completed test run. If you need to create an Azure load testing resource, see Create and run a load test.

Download Apache JMeter worker logs

When you run a load test, the Azure Load Testing test engines execute your Apache JMeter test script. During the load test, Apache JMeter stores detailed logging in the worker node logs. You can download these JMeter worker logs for each test run in the Azure portal.

For example, if there's a problem with your JMeter script, the load test status will be Failed. In the worker logs you might find additional information about the cause of the problem.

To download the worker logs for an Azure Load Testing test run, follow these steps:

  1. In the Azure portal, go to your Azure Load Testing resource.

  2. Select Tests to view the list of tests, and then select your load test.

    Screenshot that shows the list of load tests for an Azure Load Test resource.


    To limit the number of tests, use the search box and the Time range filter.

  3. Select a test run from the list to view the test run dashboard.

    Screenshot that shows a list of test runs for the selected load test.

  4. On the dashboard, select Download, and then select Logs.

    Screenshot that shows how to download the test log files from the test run details page.

    The browser should now start downloading the JMeter worker node log file worker.log.

  5. You can use a text editor to open the log file.

    Screenshot that shows the JMeter log file content.

    The worker.log file can help you diagnose the root cause of a failing load test. In the previous screenshot, you can see that the test failed because a file is missing.

Next steps