feat(logger): support VSAG_LOG_LEVEL

[wxyucs]

Change Type

• Bug fix
• New feature
• Improvement/Refactor
• Documentation
• CI/Build/Infra

Linked Issue

Not applicable for kind/improvement; no issue was provided.

What Changed

• Added VSAG_LOG_LEVEL parsing for the built-in DefaultLogger.
• Supported values: trace, debug, info, warn/warning, error, and critical.
• Invalid values are ignored so the existing default info level remains in effect.
• Documented the environment variable in English and Chinese API resource docs.

Test Evidence

• make fmt
• make lint
• make test
• make cov, run tests, and collect coverage
• Other (describe below)

Test details:

# TDD check before implementation: failed as expected
./build/tests/unittests "DefaultLogger uses VSAG_LOG_LEVEL"

clang-format-15 -i src/impl/logger/default_logger.cpp src/impl/logger/default_logger.h src/impl/logger/default_logger_test.cpp
cmake --build ./build --target unittests --parallel 96
./build/tests/unittests "DefaultLogger*"
# All tests passed (6 assertions in 5 test cases)

./build/tests/unittests "[ut][logger]"
# All tests passed (11 assertions in 7 test cases)

git diff --check

Compatibility Impact

• API/ABI compatibility: no public API change.
• Behavior changes: the built-in logger now reads VSAG_LOG_LEVEL when it is constructed; explicit SetLevel calls still override it.

Performance and Concurrency Impact

• Performance impact: none expected; parsing happens once at logger construction.
• Concurrency/thread-safety impact: none expected.

Documentation Impact

• No docs update needed
• Updated docs:
  • README.md
  • DEVELOPMENT.md
  • CONTRIBUTING.md
  • Other: docs/docs/en/src/api/resource.md, docs/docs/zh/src/api/resource.md

Risk and Rollback

• Risk level: low
• Rollback plan: revert this commit.

Checklist

• I have linked the relevant issue (required for kind/bug and kind/feature; see "Linked Issue" above)
• I have added/updated tests for new behavior or bug fixes
• I have considered API compatibility impact
• I have updated docs if behavior/workflow changed
• My commit messages follow project conventions (Conventional Commits, optional [skip ci] prefix)

[mergify]

Merge Protections

🟢 All 2 merge protections satisfied — ready to merge.

Show 2 satisfied protections

🟢 Require kind label

• label~=^kind/

🟢 Require version label

• label~=^version/

[gemini-code-assist]

Code Review

This pull request introduces the ability to configure the log level of the built-in logger using the VSAG_LOG_LEVEL environment variable, including updates to English and Chinese documentation, implementation of a case-insensitive log level parser, and comprehensive unit tests. The reviewer feedback suggests avoiding virtual function calls in the constructor by directly updating the atomic log level, adding a length guard to the parser to prevent unnecessary allocations, and supporting as well as documenting the "off" log level to completely disable logging.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[Copilot]

Pull request overview

Adds support for configuring the built-in vsag::DefaultLogger log level via a VSAG_LOG_LEVEL environment variable, and documents this behavior in the API “Resource” docs (EN/ZH). This fits into VSAG’s runtime configuration surface by allowing users to adjust default logging verbosity without changing code.

Changes:

• Added VSAG_LOG_LEVEL parsing at DefaultLogger construction time with support for trace, debug, info, warn/warning, error, critical (invalid values are ignored).
• Added unit tests covering env-driven level selection, alias handling, invalid input fallback, and explicit SetLevel override behavior.
• Documented VSAG_LOG_LEVEL usage in English and Chinese API resource docs.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/impl/logger/default_logger.h	Declares an explicit DefaultLogger() constructor to enable env-based initialization.
src/impl/logger/default_logger.cpp	Implements VSAG_LOG_LEVEL parsing and applies the parsed level during logger construction.
src/impl/logger/default_logger_test.cpp	Adds Catch2 tests and small RAII helpers for env/stream capture to validate new behavior.
docs/docs/en/src/api/resource.md	Documents VSAG_LOG_LEVEL behavior and supported values (EN).
docs/docs/zh/src/api/resource.md	Documents VSAG_LOG_LEVEL behavior and supported values (ZH).

[wxyucs]

/assign @wxyucs

[vsag-bot]

/label S-ready-to-merge
/waiting-on maintainer
/request-review @jiaweizone
/request-review @inabao

[LHT129]

LGTM

[mergify]

Tick the box to add this pull request to the merge queue (same as @mergifyio queue).

• Queue this pull request