model_retry.py — langchain Source File

Source Code

"""Model retry middleware for agents."""

from __future__ import annotations

import asyncio
import time
from typing import TYPE_CHECKING

from langchain_core.messages import AIMessage

from langchain.agents.middleware._retry import (
    OnFailure,
    RetryOn,
    calculate_delay,
    should_retry_exception,
    validate_retry_params,
)
from langchain.agents.middleware.types import (
    AgentMiddleware,
    AgentState,
    ContextT,
    ModelRequest,
    ModelResponse,
    ResponseT,
)

if TYPE_CHECKING:
    from collections.abc import Awaitable, Callable


class ModelRetryMiddleware(AgentMiddleware[AgentState[ResponseT], ContextT, ResponseT]):
    """Middleware that automatically retries failed model calls with configurable backoff.

    Supports retrying on specific exceptions and exponential backoff.

    Examples:
        !!! example "Basic usage with default settings (2 retries, exponential backoff)"

            ```python
            from langchain.agents import create_agent
            from langchain.agents.middleware import ModelRetryMiddleware

            agent = create_agent(model, tools=[search_tool], middleware=[ModelRetryMiddleware()])
            ```

        !!! example "Retry specific exceptions only"

            ```python
            from anthropic import RateLimitError
            from openai import APITimeoutError

            retry = ModelRetryMiddleware(
                max_retries=4,
                retry_on=(APITimeoutError, RateLimitError),
                backoff_factor=1.5,
            )
            ```

        !!! example "Custom exception filtering"

// ... (253 more lines)