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on_chain_start() — langchain Function Reference

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

Function python Observability CallbackManager calls 2 called by 2

Entity Profile

Dependency Diagram

graph TD
  1b37e7f7_9f67_e0c5_eb5f_dffa98170394["on_chain_start()"]
  f2c19eb2_a092_16e7_b693_b7ae35a0bc8c["CallbackManager"]
  1b37e7f7_9f67_e0c5_eb5f_dffa98170394 -->|defined in| f2c19eb2_a092_16e7_b693_b7ae35a0bc8c
  61bdaf3c_38ed_e800_b567_b934b7b71aaa["on_chain_start()"]
  61bdaf3c_38ed_e800_b567_b934b7b71aaa -->|calls| 1b37e7f7_9f67_e0c5_eb5f_dffa98170394
  e694e06d_9c3a_9620_74b6_743814a492ce["trace_as_chain_group()"]
  e694e06d_9c3a_9620_74b6_743814a492ce -->|calls| 1b37e7f7_9f67_e0c5_eb5f_dffa98170394
  61bdaf3c_38ed_e800_b567_b934b7b71aaa["on_chain_start()"]
  1b37e7f7_9f67_e0c5_eb5f_dffa98170394 -->|calls| 61bdaf3c_38ed_e800_b567_b934b7b71aaa
  8964b4e9_440e_18a7_2a15_a54a0b2b733c["handle_event()"]
  1b37e7f7_9f67_e0c5_eb5f_dffa98170394 -->|calls| 8964b4e9_440e_18a7_2a15_a54a0b2b733c
  style 1b37e7f7_9f67_e0c5_eb5f_dffa98170394 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/callbacks/manager.py lines 1412–1455

    def on_chain_start(
        self,
        serialized: dict[str, Any] | None,
        inputs: dict[str, Any] | Any,
        run_id: UUID | None = None,
        **kwargs: Any,
    ) -> CallbackManagerForChainRun:
        """Run when chain starts running.

        Args:
            serialized: The serialized chain.
            inputs: The inputs to the chain.
            run_id: The ID of the run.
            **kwargs: Additional keyword arguments.

        Returns:
            The callback manager for the chain run.

        """
        if run_id is None:
            run_id = uuid7()
        handle_event(
            self.handlers,
            "on_chain_start",
            "ignore_chain",
            serialized,
            inputs,
            run_id=run_id,
            parent_run_id=self.parent_run_id,
            tags=self.tags,
            metadata=self.metadata,
            **kwargs,
        )

        return CallbackManagerForChainRun(
            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,
        )

Domain

Subdomains

Defined In

Calls

Called By

Source

Frequently Asked Questions

What does on_chain_start() do?
on_chain_start() is a function in the langchain codebase, defined in libs/core/langchain_core/callbacks/manager.py.
Where is on_chain_start() defined?
on_chain_start() is defined in libs/core/langchain_core/callbacks/manager.py at line 1412.
What does on_chain_start() call?
on_chain_start() calls 2 function(s): handle_event, on_chain_start.
What calls on_chain_start()?
on_chain_start() is called by 2 function(s): on_chain_start, trace_as_chain_group.

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