Langchain instrumentor implementation

docs/instrumentation-genai/langchain/langchain.rst

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+OpenTelemetry Jinja2 Instrumentation
+====================================
+
+.. automodule:: opentelemetry.instrumentation.langchain
+    :members:
+    :undoc-members:
+    :show-inheritance:

instrumentation-genai/opentelemetry-instrumentation-langchain/src/opentelemetry/instrumentation/langchain/__init__.py

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+from typing import Collection
+from opentelemetry.instrumentation.instrumentor import BaseInstrumentor
+from wrapt import wrap_function_wrapper
+
+from opentelemetry.trace import get_tracer
+from opentelemetry.instrumentation.utils import unwrap
+
+# from opentelemetry.instrumentation.langchain_v2.version import __version__
+from opentelemetry.instrumentation.langchain.version import __version__
+from opentelemetry.instrumentation.langchain_v2.callback_handler import OpenTelemetryCallbackHandler
+from opentelemetry.instrumentation.langchain_v2.async_callback_handler import OpenTelemetryAsyncCallbackHandler
+
+
+__all__ = ["OpenTelemetryCallbackHandler"]
+
+_instruments = ("langchain >= 0.1.0",)
+
+class LangChainInstrumentor(BaseInstrumentor):
+
+    def instrumentation_dependencies(cls) -> Collection[str]:
+        return _instruments
+
+    def _instrument(self, **kwargs):
+        tracer_provider = kwargs.get("tracer_provider")
+        tracer = get_tracer(__name__, __version__, tracer_provider)
+
+        otelCallbackHandler = OpenTelemetryCallbackHandler(tracer)
+
+        wrap_function_wrapper(
+            module="langchain_core.callbacks",
+            name="BaseCallbackManager.__init__",
+            wrapper=_BaseCallbackManagerInitWrapper(otelCallbackHandler),
+        )
+
+    def _uninstrument(self, **kwargs):
+        unwrap("langchain_core.callbacks", "BaseCallbackManager.__init__")
+        if hasattr(self, "_wrapped"):
+            for module, name in self._wrapped:
+                unwrap(module, name)
+        self.handler = None
+
+class _BaseCallbackManagerInitWrapper:
+    def __init__(self, callback_handler: "OpenTelemetryCallbackHandler"):
+        self.callback_handler = callback_handler
+        self._wrapped = []
+
+    def __call__(
+        self,
+        wrapped,
+        instance,
+        args,
+        kwargs,
+    ) -> None:
+        wrapped(*args, **kwargs)
+        for handler in instance.inheritable_handlers:
+            if isinstance(handler, OpenTelemetryCallbackHandler):
+                return None
+        else:
+            instance.add_handler(self.callback_handler, True)