Simple aiohttp retry client
Python 3.7 or higher.
Install: pip install aiohttp-retry.
Breaking API changes
- Since 2.5.6 this is a new parameter in
get_timeoutfunc called "response".
If you have defined your ownRetryOptions, you should add this param into it. Issue about this: #59
Examples of usage:
from aiohttp_retry import RetryClient, ExponentialRetry
async def main():
retry_options = ExponentialRetry(attempts=1)
retry_client = RetryClient(raise_for_status=False, retry_options=retry_options)
async with retry_client.get('https://ya.ru') as response:
print(response.status)
await retry_client.close()from aiohttp import ClientSession
from aiohttp_retry import RetryClient
async def main():
client_session = ClientSession()
retry_client = RetryClient(client_session=client_session)
async with retry_client.get('https://ya.ru') as response:
print(response.status)
await client_session.close()from aiohttp_retry import RetryClient, RandomRetry
async def main():
retry_options = RandomRetry(attempts=1)
retry_client = RetryClient(raise_for_status=False, retry_options=retry_options)
response = await retry_client.get('/ping')
print(response.status)
await retry_client.close()from aiohttp_retry import RetryClient
async def main():
async with RetryClient() as client:
async with client.get('https://ya.ru') as response:
print(response.status)You can also add some logic, F.E. logging, on failures by using trace mechanic.
import logging
import sys
from types import SimpleNamespace
from aiohttp import ClientSession, TraceConfig, TraceRequestStartParams
from aiohttp_retry import RetryClient, ExponentialRetry
handler = logging.StreamHandler(sys.stdout)
logging.basicConfig(handlers=[handler])
logger = logging.getLogger(__name__)
retry_options = ExponentialRetry(attempts=2)
async def on_request_start(
session: ClientSession,
trace_config_ctx: SimpleNamespace,
params: TraceRequestStartParams,
) -> None:
current_attempt = trace_config_ctx.trace_request_ctx['current_attempt']
if retry_options.attempts <= current_attempt:
logger.warning('Wow! We are in last attempt')
async def main():
trace_config = TraceConfig()
trace_config.on_request_start.append(on_request_start)
retry_client = RetryClient(retry_options=retry_options, trace_configs=[trace_config])
response = await retry_client.get('https://httpstat.us/503', ssl=False)
print(response.status)
await retry_client.close()Look tests for more examples.
Be aware: last request returns as it is.
If the last request ended with exception, that this exception will be raised from RetryClient request
Documentation
RetryClient takes the same arguments as ClientSession[docs]
RetryClient has methods:
- get
- options
- head
- post
- put
- patch
- put
- delete
They are same as for ClientSession, but take one possible additional argument:
class RetryOptionsBase:
def __init__(
self,
attempts: int = 3, # How many times we should retry
statuses: Optional[Iterable[int]] = None, # On which statuses we should retry
exceptions: Optional[Iterable[Type[Exception]]] = None, # On which exceptions we should retry
retry_all_server_errors: bool = True, # If should retry all 500 errors or not
# a callback that will run on response to decide if retry
evaluate_response_callback: Optional[EvaluateResponseCallbackType] = None,
):
...
@abc.abstractmethod
def get_timeout(self, attempt: int, response: Optional[Response] = None) -> float:
raise NotImplementedErrorYou can specify RetryOptions both for RetryClient and it's methods.
RetryOptions in methods override RetryOptions defined in RetryClient constructor.
Important: by default all 5xx responses are retried + statuses you specified as statuses param
If you will pass retry_all_server_errors=False than you can manually set what 5xx errors to retry.
You can define your own timeouts logic or use:
-
ExponentialRetrywith exponential backoff -
RandomRetryfor random backoff -
ListRetrywith backoff you predefine by list -
FibonacciRetrywith backoff that looks like fibonacci sequence -
JitterRetryexponential retry with a bit of randomness
Important: you can proceed server response as an parameter for calculating next timeout.
However this response can be None, server didn't make a response or you have set up raise_for_status=True
Look here for an example: #59
Additionally, you can specify evaluate_response_callback. It receive a ClientResponse and decide to retry or not by returning a bool.
It can be useful, if server API sometimes response with malformed data.
Request Trace Context
RetryClient add current attempt number to request_trace_ctx (see examples,
for more info see aiohttp doc).
Change URL between retries
You can change URL between retries by specifying url as list of urls. Example:
from aiohttp_retry import RetryClient
retry_client = RetryClient()
async with retry_client.get(url=['/internal_error', '/ping']) as response:
text = await response.text()
assert response.status == 200
assert text == 'Ok!'
await retry_client.close()In this example we request /interval_error, fail and then successfully request /ping.
If you specify less urls than attempts number in RetryOptions, RetryClient will request last url at last attempts.
This means that in example above we would request /ping once again in case of failure.
Types
aiohttp_retry is a typed project. It should be fully compatablie with mypy.
It also introduce one special type:
ClientType = Union[ClientSession, RetryClient]
This type can be imported by from aiohttp_retry.types import ClientType
