This project implements the JSON format used by Firefox Profiler, and uses that format to provide a simple Tracer, allowing to record nested spans in a format that can be visualised on https://profiler.firefox.com

See sample for usage:

1. Run buildSample in SBT shell
2. Load the sample-profile.json (will be created at the root of the project) into Firefox Profiler
3. My development workflow usually involves running some live reload server (with CORS), and using "Load from URL" in Firefox Profiler – this allows me to continuously rebuild the profile file and I only need to reload the Profiler tab to see the changes

// SBT
libraryDependencies += "com.indoorvivants" %% "fxprof-tracer" % "VERSION"
// Scala CLI 
//> using dep com.indoorvivants::fxprof-tracer::VERSION

All modules are

Caveats:

1. Current tracer is single threaded
2. The output looks right-ish, but not as rich as something like what samply can produce
3. At the moment profiles can only be written, not read

This work relies on a lot of trial and error because the firefox profiler format is sparsely documented, and mostly defined in a typescript file. To that end, we use a very crude code generator along with manual extensions.

Jsoniter is used for JSON serialisation.