Purpose: help customers understand the process behind Basic and Proxy authentication process and why Dynatrace reclassifies these 401 and 407 HTTP return codes as 399
This applies to Dynatrace Synthetic Classic.
The Synthetic Classic 399 error code is a reclassification of Basic (401) or Proxy (407) authentication issue when executing the test. When testing a site with authentication, the initial request returns a 401 or 407 error to challenge the browser to respond with username/password. The Browser Engine then requests the page again with the authentication details. Most customers do not want the first request classified as a 4xx error code and many years ago Gomez reclassified this first request as a 399. The Engine then requests the page again with the username and password stated in the script – if successful the page usually returns a 200 response and the test continues. In the case where the username and password are incorrect, the engine fails authentication a second time and another HTTP 399 error code is generated.
Note that starting with the April 2017 release, if the root and final object of a step return an HTTP 399 code we assume this is a test failure. This typically indicates a problem with the script (username invalid or password expiration), not an application availability issue, so we classify the result as an error but do not count this as an availability issue.