aioretry
Asyncio retry utility for Python 3.7+
Install
$ pip install aioretryUsage
import asyncio
from typing import (
Tuple
)
from aioretry import (
retry,
# Tuple[bool, Union[int, float]]
RetryPolicyStrategy,
RetryInfo
)
# This example shows the usage with python typings
def retry_policy(info: RetryInfo) -> RetryPolicyStrategy:
"""
- 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, (info.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, info: RetryInfo) -> RetryPolicyStrategy:
return info.fails > self._max_retries, info.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, info: RetryInfo) -> None:
await self._send_failure_log(info.exception, info.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(info: RetryInfo) -> RetryPolicyStrategy:
if isinstance(info.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[[RetryInfo], Optional[Awaitable]]]]If specified,before_retryis called after each failure offnand before the corresponding retry. If the retry is abandoned,before_retrywill not be executed.
Returns a wrapped function which accepts the same arguments as fn and returns an Awaitable.
RetryPolicy
RetryPolicy = Callable[[RetryInfo], 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(info)-
info
RetryInfo-
info.fails
intis the counter number of how many times functionfnperforms as a failure. Iffnfails for the first time, thenfailswill be1. -
info.exception
Exceptionis the exception thatfnraised. -
info.since
datetimeis the datetime when the first failure happens.
-
info.fails
- If
abandonisTrue, then aioretry will give up the retry and raise the exception directly, otherwise aioretry will sleepdelayseconds (asyncio.sleep(delay)) before the next retry.
def retry_policy(info: RetryInfo):
if isinstance(info.exception, KeyError):
# Just raise exceptions of type KeyError
return True, 0
return False, info.fails * 0.1Python 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,
RetryInfo
)Upgrade guide
Since 5.0.0, aioretry introduces RetryInfo as the only parameter of retry_policy or before_retry
2.x -> 5.x
2.x
def retry_policy(fails: int):
"""A policy that gives no chances to retry
"""
return True, 0.1 * fails5.x
def retry_policy(info: RetryInfo):
return True, 0.1 * info.fails3.x -> 5.x
3.x
def before_retry(e: Exception, fails: int):
...5.x
# Change the sequence of the parameters
def before_retry(info: RetryInfo):
info.exception
info.fails
...4.x -> 5.x
Since 5.0.0, both retry_policy and before_retry have only one parameter of type RetryInfo respectively.
