_retry.py — langchain Source File

Source Code

"""Shared retry utilities for agent middleware.

This module contains common constants, utilities, and logic used by both
model and tool retry middleware implementations.
"""

from __future__ import annotations

import random
from collections.abc import Callable
from typing import Literal

# Type aliases
RetryOn = tuple[type[Exception], ...] | Callable[[Exception], bool]
"""Type for specifying which exceptions to retry on.

Can be either:
- A tuple of exception types to retry on (based on `isinstance` checks)
- A callable that takes an exception and returns `True` if it should be retried
"""

OnFailure = Literal["error", "continue"] | Callable[[Exception], str]
"""Type for specifying failure handling behavior.

Can be either:
- A literal action string (`'error'` or `'continue'`)
    - `'error'`: Re-raise the exception, stopping agent execution.
    - `'continue'`: Inject a message with the error details, allowing the agent to continue.
       For tool retries, a `ToolMessage` with the error details will be injected.
       For model retries, an `AIMessage` with the error details will be returned.
- A callable that takes an exception and returns a string for error message content
"""


def validate_retry_params(
    max_retries: int,
    initial_delay: float,
    max_delay: float,
    backoff_factor: float,
) -> None:
    """Validate retry parameters.

    Args:
        max_retries: Maximum number of retry attempts.
        initial_delay: Initial delay in seconds before first retry.
        max_delay: Maximum delay in seconds between retries.
        backoff_factor: Multiplier for exponential backoff.

    Raises:
        ValueError: If any parameter is invalid (negative values).
    """
    if max_retries < 0:
        msg = "max_retries must be >= 0"
        raise ValueError(msg)
    if initial_delay < 0:
        msg = "initial_delay must be >= 0"
        raise ValueError(msg)
    if max_delay < 0:
        msg = "max_delay must be >= 0"
        raise ValueError(msg)
// ... (64 more lines)