#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import asyncio
import functools
import time
from contextlib import contextmanager
from logging import Logger
from typing import Any, Generator, List, Optional, Tuple, Type
MAX_WAIT_SECONDS: int = 600
[docs]def retry_on_exception(
exception_types: Optional[Tuple[Type[Exception], ...]] = None,
no_retry_on_exception_types: Optional[Tuple[Type[Exception], ...]] = None,
check_message_contains: Optional[List[str]] = None,
retries: int = 3,
suppress_all_errors: bool = False,
logger: Optional[Logger] = None,
default_return_on_suppression: Optional[Any] = None,
wrap_error_message_in: Optional[str] = None,
initial_wait_seconds: Optional[int] = None,
) -> Optional[Any]:
"""
A decorator for instance methods or standalone functions that makes them
retry on failure and allows to specify on which types of exceptions the
function should and should not retry.
NOTE: If the argument `suppress_all_errors` is supplied and set to True,
the error will be suppressed and default value returned.
Args:
exception_types: A tuple of exception(s) types to catch in the decorated
function. If none is provided, baseclass Exception will be used.
no_retry_on_exception_types: Exception types to consider non-retryable even
if their supertype appears in `exception_types` or the only exceptions to
not retry on if no `exception_types` are specified.
check_message_contains: A list of strings, against which to match error
messages. If the error message contains any one of these strings,
the exception will cause a retry. NOTE: This argument works in
addition to `exception_types`; if those are specified, only the
specified types of exceptions will be caught and retried on if they
contain the strings provided as `check_message_contains`.
retries: Number of retries to perform.
suppress_all_errors: If true, after all the retries are exhausted, the
error will still be suppressed and `default_return_on_suppresion`
will be returned from the function. NOTE: If using this argument,
the decorated function may not actually get fully executed, if
it consistently raises an exception.
logger: A handle for the logger to be used.
default_return_on_suppression: If the error is suppressed after all the
retries, then this default value will be returned from the function.
Defaults to None.
wrap_error_message_in: If raising the error message after all the retries,
a string wrapper for the error message (useful for making error
messages more user-friendly). NOTE: Format of resulting error will be:
"<wrap_error_message_in>: <original_error_type>: <original_error_msg>",
with the stack trace of the original message.
initial_wait_seconds: Initial length of time to wait between failures,
doubled after each failure up to a maximum of 10 minutes. If unspecified
then there is no wait between retries.
"""
def func_wrapper(func):
# Depending on whether `func` is async or not, we use a slightly different
# wrapper; if wrapping an async function, decorator will await it.
# `async_actual_wrapper` and `actual_wrapper` are almost exactly the same,
# except that the former is async and awaits the wrapped function.
if asyncio.iscoroutinefunction(func):
@functools.wraps(func)
async def async_actual_wrapper(*args, **kwargs):
(
retry_exceptions,
no_retry_exceptions,
suppress_errors,
) = _validate_and_fill_defaults(
retry_on_exception_types=exception_types,
no_retry_on_exception_types=no_retry_on_exception_types,
suppress_errors=suppress_all_errors,
**kwargs,
)
for i in range(retries):
with handle_exceptions_in_retries(
no_retry_exceptions=no_retry_exceptions,
retry_exceptions=retry_exceptions,
suppress_errors=suppress_errors,
check_message_contains=check_message_contains,
last_retry=i >= retries - 1,
logger=logger,
wrap_error_message_in=wrap_error_message_in,
):
if i > 0 and initial_wait_seconds is not None:
wait_interval = min(
MAX_WAIT_SECONDS, initial_wait_seconds * 2 ** (i - 1)
)
asyncio.sleep(wait_interval)
return await func(*args, **kwargs)
# If we are here, it means the retries were finished but
# The error was suppressed. Hence return the default value provided.
return default_return_on_suppression
return async_actual_wrapper
@functools.wraps(func)
def actual_wrapper(*args, **kwargs):
(
retry_exceptions,
no_retry_exceptions,
suppress_errors,
) = _validate_and_fill_defaults(
retry_on_exception_types=exception_types,
no_retry_on_exception_types=no_retry_on_exception_types,
suppress_errors=suppress_all_errors,
**kwargs,
)
for i in range(retries):
with handle_exceptions_in_retries(
no_retry_exceptions=no_retry_exceptions,
retry_exceptions=retry_exceptions,
suppress_errors=suppress_errors,
check_message_contains=check_message_contains,
last_retry=i >= retries - 1,
logger=logger,
wrap_error_message_in=wrap_error_message_in,
):
if i > 0 and initial_wait_seconds is not None:
wait_interval = min(
MAX_WAIT_SECONDS, initial_wait_seconds * 2 ** (i - 1)
)
time.sleep(wait_interval)
return func(*args, **kwargs)
# If we are here, it means the retries were finished but
# The error was suppressed. Hence return the default value provided.
return default_return_on_suppression
return actual_wrapper
return func_wrapper
[docs]@contextmanager
def handle_exceptions_in_retries(
no_retry_exceptions: Tuple[Type[Exception], ...],
retry_exceptions: Tuple[Type[Exception], ...],
suppress_errors: bool,
check_message_contains: Optional[str],
last_retry: bool,
logger: Optional[Logger],
wrap_error_message_in: Optional[str],
) -> Generator[None, None, None]:
try:
yield # Perform action within the context manager.
except no_retry_exceptions:
raise
except retry_exceptions as err: # Exceptions is a tuple.
err_msg = getattr(err, "message", repr(err))
if not last_retry or suppress_errors:
# We are either explicitly asked to suppress the error
# or we have retries left.
if logger is not None:
# `logger.exception` automatically logs `err` and its stack trace.
logger.exception(err)
elif (
not last_retry
and check_message_contains is not None
and any(message in err_msg for message in check_message_contains)
):
# In this case, the error is just logged, suppressed and default
# value returned
if logger is not None:
logger.exception(wrap_error_message_in)
elif not wrap_error_message_in:
raise
else:
msg = f"{wrap_error_message_in}: {type(err).__name__}: {str(err)}"
raise type(err)(msg).with_traceback(err.__traceback__)
def _validate_and_fill_defaults(
retry_on_exception_types: Optional[Tuple[Type[Exception], ...]],
no_retry_on_exception_types: Optional[Tuple[Type[Exception], ...]],
suppress_errors: bool,
**kwargs: Any,
) -> Tuple[Tuple[Type[Exception], ...], Tuple[Type[Exception], ...], bool]:
if retry_on_exception_types is None:
# If no exception type provided, we catch all errors.
retry_on_exception_types = (Exception,)
if not isinstance(retry_on_exception_types, tuple):
raise ValueError("Expected a tuple of exception types.")
if no_retry_on_exception_types is not None:
if not isinstance(no_retry_on_exception_types, tuple):
raise ValueError("Expected a tuple of non-retriable exception types.")
if set(no_retry_on_exception_types).intersection(set(retry_on_exception_types)):
raise ValueError(
"Same exception type cannot appear in both "
"`exception_types` and `no_retry_on_exception_types`."
)
# `suppress_all_errors` could be a flag to the underlying function
# when used on instance methods.
suppress_errors = suppress_errors or kwargs.get("suppress_all_errors", False)
return retry_on_exception_types, no_retry_on_exception_types or (), suppress_errors
