fix: Logger.Enabled()

[proost]

Fixes #2667

Changes

fix to Logger.Enabled() use severity. so it changes to default behavior that enabled all logs to emit.

I fix it as minimal what original issue mentioned. But the issue reported two years ago, spec is changed.

do I need to follow "DEVELOPMENT" status spec?(https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#enabled)

I think adding features to "LoggerConfig" is correct to me(default behavior can be annoyed because all logs enabled). But this is my first time, so I don't know what is rule in this project.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: proost / name: lani_karrot (22c01e3, 3e395c6)
• ✅ login: proost / name: proost (091a649, 35b6177, 3a59302, 40c576e, 6714614, 698e834, 7138337, 7e97ad8, 813f4fe, 824fa05, 8f0e119, b238ee7, c280e77, c48f823, ca4f1ba, e156c57, fa276f4, fb5c197)

[codecov]

Codecov Report

❌ Patch coverage is 85.54217% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.08%. Comparing base (dbf6567) to head (22c01e3).

Files with missing lines	Patch %	Lines
api/include/opentelemetry/logs/logger.h	64.52%	11 Missing ⚠️
sdk/src/logs/logger.cc	96.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4011      +/-   ##
==========================================
+ Coverage   82.06%   82.08%   +0.03%     
==========================================
  Files         385      385              
  Lines       15891    15978      +87     
==========================================
+ Hits        13039    13114      +75     
- Misses       2852     2864      +12     

Files with missing lines	Coverage Δ
sdk/include/opentelemetry/sdk/logs/logger_config.h	100.00% <100.00%> (ø)
sdk/include/opentelemetry/sdk/logs/processor.h	100.00% <100.00%> (ø)
sdk/src/logs/logger_config.cc	100.00% <100.00%> (ø)
sdk/src/logs/multi_log_record_processor.cc	93.25% <100.00%> (+0.82%)	⬆️
sdk/src/logs/multi_recordable.cc	90.55% <ø> (ø)
sdk/src/logs/logger.cc	90.79% <96.30%> (+2.79%)	⬆️
api/include/opentelemetry/logs/logger.h	68.84% <64.52%> (+3.97%)	⬆️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[marcalff]

do I need to follow "DEVELOPMENT" status spec?(https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#enabled)

Yes.

The spec in "development" status means some changes are still possible before it reaches a stable state.

SDK like opentelemetry-cpp needs to implement these specs early (so, now), to discover possible issues with the spec, so it can be adjusted if needed before reaching the stable status.

Thanks for the contribution.

[proost]

@marcalff @lalitb
I changed code to follow current api/sdk specs. If community is ok, can I divide fixing "EmitLogRecord" another PR? Because I think current change is meaningful and big enough.

[proost]

current code default is trace. if this is intended, I will rollback to current code.

[dbarker]

@proost Thanks for the PR! Both the LoggerConfig and YAML parsing/building features are very much needed :)

The PR has grown a bit beyond the initial issue. To facilitate review please break out the yaml config parsing to a separate PR as follow up to this one.

[lalitb]

@proost - Thanks for fixing the earlier ShouldEmitLogRecord(...) case.

I think the same concern still matters for Enabled(severity) itself. Enabled() is called from application /
instrumentation code as the guard before doing expensive log work, so this is one of the most important hot paths in
the logs API.

For example:

  if (logger->Enabled(Severity::kDebug)) {
    // allocate/build expensive debug log payload
  }

When debug logging is disabled, applications should pay as little as possible here. Previously this was just the
cached minimum-severity check. With the current code, the disabled path can still pay for runtime-context lookup and
virtual dispatch through Logger::EnabledImplementation(...) / LogRecordProcessor::Enabled(...).

Can we preserve the severity-only fast path for Enabled(severity), so disabled logging remains just the cheap
cached check, and only use the context / processor filtering path when that extra filtering is explicitly configured?

@ThomsonTan - Can you have a quick look on this PR too. Thanks.