Add langchain instrumentation

[Radhika Gupta (rads-1996)]

No description provided.

[Copilot]

Pull request overview

Adds first-party LangChain instrumentation to the Microsoft OpenTelemetry Python distro by introducing a LangChain BaseTracer implementation, an OTel BaseInstrumentor entry point for auto-discovery, and accompanying unit tests + sample.

Changes:

• Introduce genai._langchain module with attribute-extraction utilities, a LangChain tracer that emits OTel spans, and an instrumentor that hooks BaseCallbackManager.
• Register langchain as a supported/preview instrumentation and add an opentelemetry_instrumentor entry point.
• Add a LangChain sample and a dedicated tests/langchain/ test suite.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/langchain/test_utils.py	Unit tests for LangChain → OTel attribute extraction helpers.
tests/langchain/test_tracer.py	Unit tests for tracer span lifecycle, agent wrapper spans, and aggregation behavior.
tests/langchain/test_tracer_instrumentor.py	Unit tests for instrumentor wiring and callback-manager hook behavior.
tests/langchain/init.py	Marks tests.langchain as a package.
src/microsoft/opentelemetry/_constants.py	Adds langchain to supported instrumented libraries list.
src/microsoft/opentelemetry/_azure_monitor/_constants.py	Adds langchain to preview/opt-in instrumentations.
src/genai/_langchain/_utils.py	Implements core extraction/normalization utilities and OTel GenAI attribute mapping.
src/genai/_langchain/_tracer.py	Implements LangChainTracer that creates spans for runs and aggregates agent content.
src/genai/_langchain/_tracer_instrumentor.py	Adds OTel BaseInstrumentor to attach tracer to LangChain callback managers + convenience APIs.
src/genai/_langchain/init.py	Exposes LangChainInstrumentor.
src/genai/init.py	Introduces genai package.
samples/langchain/sample_langchain_instrumentation.py	Demonstrates enabling LangChain instrumentation and running LLM + agent flows.
pyproject.toml	Adds dependencies + registers the langchain instrumentor entry point.

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