Adding telemetry for debugger time-to-start performance

[karthiknadig]

For #7332

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Has a news entry file (remember to thank yourself!)
• Appropriate comments and documentation strings in the code
  - [ ] Has sufficient logging.
• Has telemetry for enhancements.
  - [ ] Unit tests & system/integration tests are added/updated
  - [ ] Test plan is updated as appropriate
  - [ ] package-lock.json has been regenerated by running npm install (if dependencies have changed)
  - [ ] The wiki is updated with any design decisions/details.

[karthiknadig]

@luabud is there work item for this in the extension repo? I can create one if not. I will update that and the news item after.

[codecov-io]

Codecov Report

Merging #7323 into master will decrease coverage by 0.06%.
The diff coverage is 47.82%.

@@            Coverage Diff             @@
##           master    #7323      +/-   ##
==========================================
- Coverage   58.36%   58.29%   -0.07%     
==========================================
  Files         493      493              
  Lines       21667    21690      +23     
  Branches     3486     3489       +3     
==========================================
  Hits        12645    12645              
- Misses       8242     8266      +24     
+ Partials      780      779       -1

Impacted Files	Coverage Δ
src/client/telemetry/index.ts	86.13% <ø> (ø)	⬆️
src/client/debugger/types.ts	100% <ø> (ø)	⬆️
src/client/telemetry/constants.ts	100% <100%> (ø)	⬆️
src/client/datascience/debugLocationTracker.ts	69.56% <36.84%> (-12.44%)	⬇️
src/client/common/logger.ts	68.55% <0%> (-6.92%)	⬇️

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[kimadeline]

I approved the DS changes, but there are still extension changes pending 🤦‍♀

[DonJayamanne]

This seems to measure just the data science debugger, not the standard debugger user by extension!
Shouldn't we do it for both, in a more generic way? I.e. benefit everyone.
This way we can add more telemetry in the future for other bits as well.

Also the class modified is named debugLocationTracker, doesn't feel like the right place to add this perf stuff.
I'd prefer if we created a separate tracker class for perf, and moved it out of data science folder to make it generic to the entire Extension.

[karthiknadig]

@DonJayamanne You can register only one tracker per language. This runs for anytime a debug configuration has language python. Let me know if you have any suggestion on reorganizing this.

[karthiknadig]

Note that there are a bunch of issues with the tracker here.

1. The DS tracker does not isolate itself from non-DS scenarios. This tracker is used in all debug sessions where the language is python.
2. The DS tracker factory reuses a single tracker instance. The debug session is updated on it when ever a new session starts. This breaks in multi proc scenario where there can be multiple simultaneous debug sessions.

Let me know if I can go ahead and make the change to create a global tracker for python and let DS register itself with that. The DA can register telemetry with that too. Essentially observer pattern.

[karthiknadig]

Talked to @kimadeline created a separate item to track the refactor of this tracker https://github.com/microsoft/vscode-python/issues/7352