How do you know when to debug a REST API?

Debug a REST API when encountering issues such as unexpected errors, incorrect data responses, or functionality failures. Utilize logging to track request and response details. Employ debugging tools like Postman or cURL for manual testing. Monitor server logs for error messages. Use breakpoints in code during development. Regularly test API endpoints to catch potential bugs early. Debugging is essential whenever the API's behavior deviates from the expected outcomes to ensure optimal performance.

Some telltale signs of a faulty API are inconsistent and unpredictable responses, poor performance, and unexplained errors. These issues are evident when the agreement defined as the request/response for each part of the API is not met, the API times out, and there are frequent server errors (HTTP status 5xx) or client-side errors (HTTP status 4xx) without clear and understandable error messages being displayed.

Obviously unexpected response shows a lousy & improfessional API. Meanwhile slow performance is a great signal for faulty API which needs debugging & recheck!

Signs of a faulty API - Poor performance, scalability issues, load test failures. If one encounters any of these, it’s a red signal and it behooves to start debugging to address the needs for effective performance.

Proper logging is essential for debugging and monitoring; it will help find the exact dates and periods when the API had problems. If you assign correct log levels like info, warnings, and errors, you can have alerts and reports that will be useful for debugging.

You can go more than the half way using Chrome DevTools & Postman! Chrome DevTools combines lots of details in one place all together, like header & body of response, errors code and a lot more ...

To debug a REST API, you can use various API clients and design tools. Some examples of these tools include Postman, Insomnia, Swagger, and RapidAPI (Paw). The simplest and most common method is to use the browser's DevTools. However, this approach may be inaccurate because the browser handles more than just API-related requests, and this can make performance checks noisy and less focused on the API itself.

In the beginning, try to define a specific area for debugging. If the API recently performed worse than usual, look first at the latest code changes and analyze how they affect the API performance; e.g., it might be some dependency update. If your API is located in different environments, test each to see if they have similar issues; you can use monitoring tools. Review each error and list them together; some are irrelevant, so you must determine where to focus. A common mistake is to focus on the first error message a person reads and ignore the rest. And when you make modifications, change one thing at a time to test if it works, then another.

Request Timeout 408 happens often. It might result from an unexpected error in the code that has yet to be caught. As a result, this function never returns the response. The API waits a certain period and produces a timeout in this case. So try to find where the system stops and delays, search for any minor error output, see what input parameters it expects, catch the error, improve documentation, and return the response. Another possible reason is that API received a request to process big data, which the function can't process before it timeouts; the solution is to notice it and produce errors like "too many results" or increase the timeout. In addition, it might result in rewriting the API to divide it into smaller and faster endpoints.