Every call in a request, in order, with timings

Trace mode instruments the whole app at build time. Turn it on and Phlo writes one JSON dump per request holding every call to a generated method, prop getter, static or native helper, with arguments and timings.

It works because the transpiler is already rewriting the code. There is no runtime interception, no debugger extension to install, no wrapper around your objects: the build injects one line at the top of every generated method, and loads a traced variant of the helper file so that esc(), arr(), loop(), view() and apply() are logged too. What you get is not a sample, it is the whole request.

The dump is structured for the two questions you actually ask. active maps file to kind to call count, which answers what got touched a lot. sequence records the order of first touch per file, which draws the path the request took through your app. Under those sits the full chronological event log.

Two small pieces of consideration. Requests to the Control Center are skipped, so looking at traces does not fill the list with traces of looking at traces. And it is stated plainly as a debugging and profiling tool rather than something to leave on: instrumenting every call costs what you would expect it to cost.

The nice property of building it this way is that there is nothing to keep in sync. Trace covers new code the moment it compiles.

Engine 1.0. See the Trace chapter.