Asyncio retry utility for Python 3.7+
Project description
aioretry
Asyncio retry utility for Python 3.7+
Install
$ pip install aioretry
Usage
import asyncio
from typing import (
Tuple
)
from aioretry import (
retry,
# Tuple[bool, Union[int, float]]
RetryPolicyStrategy
)
# This example shows the usage with python typings
def retry_policy(fails: int, _: Exception) -> RetryPolicyStrategy:
"""The second parameter of `retry_policy` is the exception,
which we will not use in this simple example.
- It will always retry until succeeded
- If fails for the first time, it will retry immediately,
- If it fails again,
aioretry will perform a 100ms delay before the second retry,
200ms delay before the 3rd retry,
the 4th retry immediately,
100ms delay before the 5th retry,
etc...
"""
return False, (fails - 1) % 3 * 0.1
@retry(retry_policy)
async def connect_to_server():
# connec to server
...
asyncio.run(connect_to_server())
Use as class instance method decorator
We could also use retry
as a decorator for instance method
class Client:
@retry(retry_policy)
async def connect(self):
await self._connect()
asyncio.run(Client().connect())
Use instance method as retry policy
retry_policy
could be the method name of the class if retry
is used as a decorator for instance method.
class ClientWithConfigurableRetryPolicy(Client):
def __init__(self, max_retries: int = 3):
self._max_retries = max_retries
def _retry_policy(self, fails: int) -> RetryPolicyStrategy:
return fails > self._max_retries, fails * 0.1
# Then aioretry will use `self._retry_policy` as the retry policy.
# And by using a str as the parameter `retry_policy`,
# the decorator must be used for instance methods
@retry('_retry_policy')
async def connect(self):
await self._connect()
asyncio.run(ClientWithConfigurableRetryPolicy(10).connect())
Register an before_retry
callback
We could also register an before_retry
callback which will be executed after every failure of the target function if the corresponding retry is not abandoned.
class ClientTrackableFailures(ClientWithConfigurableRetryPolicy):
# `before_retry` could either be a sync function or an async function
async def _before_retry(self, error: Exception, fails: int) -> None:
await self._send_failure_log(error, fails)
@retry(
retry_policy='_retry_policy',
# Similar to `retry_policy`,
# `before_retry` could either be a Callable or a str
before_retry='_before_retry'
)
async def connect(self):
await self._connect()
Only retry for certain types of exceptions
def retry_policy(fails: int, exception: Exception) -> RetryPolicyStrategy:
if isinstance(exception, (KeyError, ValueError)):
# If it raises a KeyError or a ValueError, it will not retry.
return True, 0
# Otherwise, retry immediately
return False, 0
@retry(retry_policy)
async def foo():
# do something that might raise KeyError, ValueError or RuntimeError
...
APIs
retry(retry_policy, before_retry)(fn)
- fn
Callable[[...], Awaitable]
the function to be wrapped. The function should be an async function or normal function returns an awaitable. - retry_policy
Union[str, RetryPolicy]
- before_retry?
Optional[Union[str, Callable[[Exception, int], Optional[Awaitable]]]]
If specified,before_retry
is called after each failture offn
and before the corresponding retry. If the retry is abandoned,before_retry
will not be executed.
Returns a wrapped function which accepts the same arguments as fn
and returns an Awaitable
.
RetryPolicy
RetryPolicy = Callable[[int, Exception], Tuple[bool, Union[float, int]]]
Retry policy is used to determine what to do next after the fn
fails to do some certain thing.
abandon, delay = retry_policy(fails, exception)
fails
is the counter number of how many times functionfn
performs as a failure. Iffn
fails for the first time, thenfails
will be1
exception
is the exception thatfn
raised- If
abandon
isTrue
, then aioretry will give up the retry and raise the exception directly, otherwise aioretry will sleepdelay
seconds (asyncio.sleep(delay)
) before the next retry.
def retry_policy(fails, exception):
if isinstance(exception, KeyError):
# Just raise exceptions of type KeyError
return True, 0
return False, fails * 0.1
Python typings
from aioretry import (
# The type of retry_policy function
RetryPolicy,
# The type of the return value of retry_policy function
RetryPolicyStrategy,
# The type of before_retry function
BeforeRetry
)
Upgrade guide
2.x -> 3.x
Since 3.0.0
, aioretry introduces a second positional parameter of type Exception
for retry_policy
while the function of 2.x
only has one parameters.
2.x
def retry_policy(fails: int):
"""A policy that gives no chances to retry
"""
return True, 0
3.x
def retry_policy(fails, int, _: Exception):
return True, 0
License
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