Misconfigured API requests, broken assertions, or incorrect redirects can cause a stress test to produce misleading results or fail entirely. Debugging your scenario reports the response status, assertion results, and timing details, so you can identify and fix configuration errors before launching a full-scale test. Performance Testing (PTS) supports debugging for both PTS scenarios and JMeter scenarios.
Prerequisites
Before you begin, make sure you have:
A PTS scenario or JMeter scenario. For more information, see Create a PTS scenario or Create a JMeter scenario
Run the debugger
Log on to the PTS console and choose Performance Test > Scenarios.
Find the scenario and click Edit in the Actions column.
In the lower part of the Edit Scenario page, click Debug. The Debug dialog box opens and runs the API operations in the scenario.
To minimize the Debug dialog box, click the 
icon in the upper-right corner. A pop-up window appears in the lower-right corner of the page so you can monitor progress. Click the pop-up window to restore the full dialog box.
Debug a single API operation
On the Scenario Settings tab, click Debug API next to the API operation name to debug it individually. The result appears in the dialog box after debugging completes.
PTS does not support debugging a single API operation in a virtual private cloud (VPC). To debug in a VPC, click Debug in the lower part of the Edit Scenario page to debug the entire scenario instead.
Interpret PTS debugging results
After debugging completes, the interface shows response status, assertion results, error details, and timing data for each API operation.
Response status
Each API operation displays one of the following statuses:
| Status | Meaning |
|---|---|
| HTTP status code (200, 302, 403, 500, 503, etc.) | The server returned a response. Check the code to determine whether the request succeeded. |
| Status Exception | No response was returned. Common causes include a request timeout or an incorrect request URL that contains the request body, such as an unrecognized function or an invalid URL format. |
Diagnose failures by status type
Depending on the status you see, use the following table to locate the root cause.
| Failure type | Where to look | What to check |
|---|---|---|
| Status Exception | Response Details tab > Error Information section | The error message describes the cause, such as invalid parameters or an unrecognized function. |
| Non-200 HTTP status code | Response Details tab and your application server logs | The response body for error details. Cross-reference with server-side logs to identify the root cause. |
| Assertion failure (x mark next to the API operation) | Response Details tab > Checkpoint information section | The assertion rule and actual response value. If no assertion information appears, no output parameter values were extracted. |
Error information
The Error Information section on the Response Details tab shows details about failed requests, including timeout messages, parameter errors, and connection refusals.
Timing waterfall
The Timing tab shows a waterfall chart of request time consumption across the core lifecycle. Use this chart to pinpoint where delays or errors occur during the request. All error messages can be presented in the timing waterfall.
For example, if you enabled 302 redirects in the scenario configuration, the timing waterfall shows whether a redirect occurred and the full redirect path.
Test output parameter expressions
When an API response contains data you need to extract -- typically from a TEXT-type response body -- define an output parameter using a regular expression. Test the expression during debugging to verify it returns the expected value before running a full stress test.
The expression test feature is not available for Application/JSON or TEXT/JSON response formats because these formats can be parsed directly without regular expressions.
Test a regular expression
In the right panel of the Debug dialog box, click Click to test the regular expression for the target API operation.
Configure the following parameters:
Parameter Description Source The response content to search Regular Expression The regex pattern to match Nth match Which match to return when multiple matches exist Click Test Expression to view the matching result.
If the result meets your requirements, click Sync Output Parameter to apply the expression to the API operation's output parameters.
After debugging completes, go to the Scenario Settings tab and configure the output parameter name on the Output Parameter Definition subtab.
Interpret JMeter debugging results
Click Sampler to view the request details, response details, and timing waterfall for each sampler.
Sampling log
The Sampling log section contains four tabs:
| Tab | Information displayed |
|---|---|
| General | Request URL, HTTP method, and status code |
| Request Details | Request header, body, and original packet |
| Response Details | Response header, body, and original packet |
| Timing | Time consumption of all API operations |
Engine logs
The Engine logs section shows Apache JMeter operation logs. If no sampling logs appear after debugging, you can analyze and troubleshoot issues based on the error messages in the engine logs.
For common errors and their solutions, see Common errors.