on_retriever_start() — langchain Function Reference

Architecture documentation for the on_retriever_start() function in manager.py from the langchain codebase.

Function python Observability CallbackManager calls 2 called by 1

Entity Profile

Observability→ CallbackManager→ on_retriever_start() — langchain Function Reference

Dependency Diagram

graph TD
  bef424f7_9a20_c8f6_a6d0_29ffbe00b826["on_retriever_start()"]
  f2c19eb2_a092_16e7_b693_b7ae35a0bc8c["CallbackManager"]
  bef424f7_9a20_c8f6_a6d0_29ffbe00b826 -->|defined in| f2c19eb2_a092_16e7_b693_b7ae35a0bc8c
  1a67808c_e69a_d19e_ad47_0b3b14d7a56a["on_retriever_start()"]
  1a67808c_e69a_d19e_ad47_0b3b14d7a56a -->|calls| bef424f7_9a20_c8f6_a6d0_29ffbe00b826
  1a67808c_e69a_d19e_ad47_0b3b14d7a56a["on_retriever_start()"]
  bef424f7_9a20_c8f6_a6d0_29ffbe00b826 -->|calls| 1a67808c_e69a_d19e_ad47_0b3b14d7a56a
  8964b4e9_440e_18a7_2a15_a54a0b2b733c["handle_event()"]
  bef424f7_9a20_c8f6_a6d0_29ffbe00b826 -->|calls| 8964b4e9_440e_18a7_2a15_a54a0b2b733c
  style bef424f7_9a20_c8f6_a6d0_29ffbe00b826 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/callbacks/manager.py lines 1518–1563

    def on_retriever_start(
        self,
        serialized: dict[str, Any] | None,
        query: str,
        run_id: UUID | None = None,
        parent_run_id: UUID | None = None,
        **kwargs: Any,
    ) -> CallbackManagerForRetrieverRun:
        """Run when the retriever starts running.

        Args:
            serialized: The serialized retriever.
            query: The query.
            run_id: The ID of the run.
            parent_run_id: The ID of the parent run.
            **kwargs: Additional keyword arguments.

        Returns:
            The callback manager for the retriever run.
        """
        if run_id is None:
            run_id = uuid7()

        handle_event(
            self.handlers,
            "on_retriever_start",
            "ignore_retriever",
            serialized,
            query,
            run_id=run_id,
            parent_run_id=self.parent_run_id,
            tags=self.tags,
            metadata=self.metadata,
            **kwargs,
        )

        return CallbackManagerForRetrieverRun(
            run_id=run_id,
            handlers=self.handlers,
            inheritable_handlers=self.inheritable_handlers,
            parent_run_id=self.parent_run_id,
            tags=self.tags,
            inheritable_tags=self.inheritable_tags,
            metadata=self.metadata,
            inheritable_metadata=self.inheritable_metadata,
        )