I have a webhook issue with code written in PHP on Google App Engine that is very difficult to debug. The webhook doesn't have a frontend, so to diagnose the issue I'm in a "print to syslog and redeploy to App Engine" debug cycle which is very slow. Unfortunately, the bug only appears on a production server, not local or staging servers, so my debug options are limited.
Google had a snapshot debugger to diagnose issues on a running server, but has deprecated the service. The announcement is here https://cloud.google.com/stackdriver/docs/deprecations/debugger-deprecation and says "...it remains available to use." How do I do that on App Engine? Is it really still possible to use? All documentation and support seems to have disappeared.
For reference, the original PHP debugger is on GitHub here, but the documentation links point back to Google's deprecation announcement. https://github.com/googleapis/google-cloud-php-debugger