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import abc
import socket
from time import sleep
from typing import TYPE_CHECKING, Any, Callable, Generic, Iterable, Tuple, Type, TypeVar
from redis.exceptions import ConnectionError, TimeoutError
T = TypeVar("T")
E = TypeVar("E", bound=Exception, covariant=True)
if TYPE_CHECKING:
from redis.backoff import AbstractBackoff
class AbstractRetry(Generic[E], abc.ABC):
"""Retry a specific number of times after a failure"""
_supported_errors: Tuple[Type[E], ...]
def __init__(
self,
backoff: "AbstractBackoff",
retries: int,
supported_errors: Tuple[Type[E], ...],
):
"""
Initialize a `Retry` object with a `Backoff` object
that retries a maximum of `retries` times.
`retries` can be negative to retry forever.
You can specify the types of supported errors which trigger
a retry with the `supported_errors` parameter.
"""
self._backoff = backoff
self._retries = retries
self._supported_errors = supported_errors
@abc.abstractmethod
def __eq__(self, other: Any) -> bool:
return NotImplemented
def __hash__(self) -> int:
return hash((self._backoff, self._retries, frozenset(self._supported_errors)))
def update_supported_errors(self, specified_errors: Iterable[Type[E]]) -> None:
"""
Updates the supported errors with the specified error types
"""
self._supported_errors = tuple(
set(self._supported_errors + tuple(specified_errors))
)
def get_retries(self) -> int:
"""
Get the number of retries.
"""
return self._retries
def update_retries(self, value: int) -> None:
"""
Set the number of retries.
"""
self._retries = value
class Retry(AbstractRetry[Exception]):
__hash__ = AbstractRetry.__hash__
def __init__(
self,
backoff: "AbstractBackoff",
retries: int,
supported_errors: Tuple[Type[Exception], ...] = (
ConnectionError,
TimeoutError,
socket.timeout,
),
):
super().__init__(backoff, retries, supported_errors)
def __eq__(self, other: Any) -> bool:
if not isinstance(other, Retry):
return NotImplemented
return (
self._backoff == other._backoff
and self._retries == other._retries
and set(self._supported_errors) == set(other._supported_errors)
)
def call_with_retry(
self,
do: Callable[[], T],
fail: Callable[[Exception], Any],
) -> T:
"""
Execute an operation that might fail and returns its result, or
raise the exception that was thrown depending on the `Backoff` object.
`do`: the operation to call. Expects no argument.
`fail`: the failure handler, expects the last error that was thrown
"""
self._backoff.reset()
failures = 0
while True:
try:
return do()
except self._supported_errors as error:
failures += 1
fail(error)
if self._retries >= 0 and failures > self._retries:
raise error
backoff = self._backoff.compute(failures)
if backoff > 0:
sleep(backoff)
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