aiohttp-retry 2.5.6

Simple retry client for aiohttp

Simple aiohttp retry client

Python 3.7 or higher.

Install: pip install aiohttp-retry.

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
    ):
        ...

    @abc.abstractmethod
    def get_timeout(self, attempt: int, response: Optional[Response] = None) -> float:
        raise NotImplementedError

You 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:

• ExponentialRetry with exponential backoff
• RandomRetry for random backoff
• ListRetry with backoff you predefine by list
• FibonacciRetry with backoff that looks like fibonacci sequence
• JitterRetry exponential retry with a bit of randomness

Important: you can 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: https://github.com/inyutin/aiohttp_retry/issues/59

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