feat(instrumentation): added synchronous gauge

[clintonb]

Which problem is this PR solving?

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #4296

Short description of the changes

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: clintonb / name: Clinton Blackburn (2ff80f5, 48e9cba, 42f977c)

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 92.84%. Comparing base (2610122) to head (313ce47).
Report is 23 commits behind head on main.

❗ Current head 313ce47 differs from pull request most recent head 2ff80f5. Consider uploading reports for the commit 2ff80f5 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4528      +/-   ##
==========================================
+ Coverage   90.77%   92.84%   +2.07%     
==========================================
  Files          90      328     +238     
  Lines        1930     9524    +7594     
  Branches      417     2050    +1633     
==========================================
+ Hits         1752     8843    +7091     
- Misses        178      681     +503     

Files	Coverage Δ
api/src/metrics/Metric.ts	100.00% <ø> (ø)
api/src/metrics/NoopMeter.ts	95.34% <80.00%> (-2.02%)	⬇️

... and 244 files with indirect coverage changes

[pichlermarc]

@clintonb looks awesome already. 🙂

I see this is currently a draft: when getting ready for the review, would you mind splitting the PR into two parts? So in essence:

• PR#1 SDK changes only (merged first)
• PR#2 API changes only (merged second)

The reason for that is: the SDK changes need to be functional with an older version of the API that does not include the new types. If we split that into two PRs we'll very easily be able to see if there's any adjustments that need to be made to the SDK part to ensure that it also works with the older (current) version of the API. That usually includes duplicating types from the API PR#2 into the SDK PR#1 to ensure we don't use anything that might not yet be there 🙂

[pichlermarc]

This is the case I was talking about above, where we may need to duplicate the type from @opentelemetry/api as we need to be backward compatible to @opentelemetry/api@1.3.0 which does not yet have this type. 🙂

While somewhat counter-intuitive, splitting it into two PRs where the SDK changes come first makes this a bit easier to see. 🙂

[clintonb]

@pichlermarc let me know if there is anything I need to do here and/or next steps.,

[pichlermarc]

@pichlermarc let me know if there is anything I need to do here and/or next steps.,

Sorry this is taking so long.

Turns out we need to figure out a way to add experimental metrics features to the API package as we've never done it before with new Instruments. I've opened a prototype PR to look into that #4622.

[pichlermarc]

The specification was marked stable, so we can proceed with this PR without having to go the experimental route (#4622)

While reviewing this PR I just saw that we put the Type-Parameters on the SDK implementation of the Gauge too:

opentelemetry-js/packages/sdk-metrics/src/Meter.ts

Lines 56 to 59 in 928796d

	createGauge<AttributesTypes extends Attributes = Attributes>(
	name: string,
	options?: MetricOptions
	): Gauge<AttributesTypes> {

These can be removed now as they're part of the interface we're implementing (like on the rest of the functions on the Meter class).

You may now also remove the @experimental annotations from the SDK that we added in #4565:

• opentelemetry-js/packages/sdk-metrics/src/Meter.ts

  Line 54 in 928796d

  * @experimental

• opentelemetry-js/packages/sdk-metrics/src/types.ts

  Line 29 in 928796d

  * @experimental

[clintonb]

@pichlermarc please review. 🤞🏾

[clintonb]

@pichlermarc one more look?

[clintonb]

Failing test is unrelated to this change.