A number of changes here. I recommend viewing the diff with the <a href="?w=1">whitespace flag enabled</a>.
- OpenTelemetry is replaced with a custom and lightweight tracing solution.
- Three trace targets are currently supported: console, Zipkin, and NextJS.
- Tracing is now governed by environment variables rather than `--require instrument.js`.
+ `TRACE_TARGET`: one of `CONSOLE`, `ZIPKIN`, or `TELEMETRY`; defaults to `TELEMETRY` if unset or invalid.
+ `TRACE_ID`: an 8-byte hex-encoded value used as the Zipkin trace ID; if not provided, this value will be randomly generated and passed down to subprocesses.
Other sundry:
- I'm missing something, probably a setup step, with the Zipkin target. Traces are captured successfully, but you have to manually enter the Trace ID in order to view the trace - it doesn't show up in queries.
- I'm generally unhappy with [this commit](235cedcb3e). It is... untidy to provide a telemetry object via `setGlobal`, but I don't have a ready alternative. Is `distDir` strictly required when creating a new Telemetry object? I didn't dig too deep here.
As noted, there are a lot of changes, so it'd be great if a reviewer could:
- [ ] pull down the branch and try to break it
- [ ] check the Zipkin traces and identify possible regressions in the functionality
Closes#22570Fixes#22574
@timneutkens I think this is ready for a review.
I've made some changes to the original design that _seem_ to have paid off. The parenting relationships for traces of normal builds are applied more uniformly, resulting in more intelligible traces:
<img width="900" alt="Screen Shot 2021-01-29 at 12 53 47 AM" src="https://user-images.githubusercontent.com/5016978/106253732-ba321880-61cc-11eb-98fd-d45af5078273.png">
Hot-reloading is surfaced now, too. I will note, however, that we will want to dig in deeper and find out where the large portion of time at the beginning of hot-reload is spent. Example:
<img width="894" alt="Screen Shot 2021-01-29 at 12 53 28 AM" src="https://user-images.githubusercontent.com/5016978/106253828-e057b880-61cc-11eb-967d-46eaff31ecef.png">
Where did those 180 ms go? At the least, we can now track how long a hot-reload takes, and have a place to start with further investigation.
* Add custom profiler / tracer
This captures both client/production builds and everything before and after is cpu profiled, which makes sure that the whole process instead of just webpack is included in the final report.
* Update tests
* Update profiling-plugin.js
* Rename profiling-plugin.js to profiling-plugin.ts
* Update profiling-plugin.ts
* Update and rename profiling-plugin.ts to profiling-plugin.js
* Update webpack-config.ts
* Update profiling-plugin.js
* Add types
* Add missing type
* Add back TypeScript linting
* Remove tracing-js
