fallbacks.py — langchain Source File

Source Code

"""`Runnable` that can fallback to other `Runnable` objects if it fails."""

import asyncio
import inspect
import typing
from collections.abc import AsyncIterator, Iterator, Sequence
from functools import wraps
from typing import TYPE_CHECKING, Any, cast

from pydantic import BaseModel, ConfigDict
from typing_extensions import override

from langchain_core.callbacks.manager import AsyncCallbackManager, CallbackManager
from langchain_core.runnables.base import Runnable, RunnableSerializable
from langchain_core.runnables.config import (
    RunnableConfig,
    ensure_config,
    get_async_callback_manager_for_config,
    get_callback_manager_for_config,
    get_config_list,
    patch_config,
    set_config_context,
)
from langchain_core.runnables.utils import (
    ConfigurableFieldSpec,
    Input,
    Output,
    coro_with_context,
    get_unique_config_specs,
)

if TYPE_CHECKING:
    from langchain_core.callbacks.manager import AsyncCallbackManagerForChainRun


class RunnableWithFallbacks(RunnableSerializable[Input, Output]):
    """`Runnable` that can fallback to other `Runnable` objects if it fails.

    External APIs (e.g., APIs for a language model) may at times experience
    degraded performance or even downtime.

    In these cases, it can be useful to have a fallback `Runnable` that can be
    used in place of the original `Runnable` (e.g., fallback to another LLM provider).

    Fallbacks can be defined at the level of a single `Runnable`, or at the level
    of a chain of `Runnable`s. Fallbacks are tried in order until one succeeds or
    all fail.

    While you can instantiate a `RunnableWithFallbacks` directly, it is usually
    more convenient to use the `with_fallbacks` method on a `Runnable`.

    Example:
        ```python
        from langchain_core.chat_models.openai import ChatOpenAI
        from langchain_core.chat_models.anthropic import ChatAnthropic

        model = ChatAnthropic(model="claude-3-haiku-20240307").with_fallbacks(
            [ChatOpenAI(model="gpt-3.5-turbo-0125")]
        )
        # Will usually use ChatAnthropic, but fallback to ChatOpenAI
// ... (605 more lines)