Class 08 — Connection Exception

 08000 connection_exception

 08003 connection_does_not_exist

 08006 connection_failure

 08001 sqlclient_unable_to_establish_sqlconnection

 08004 sqlserver_rejected_establishment_of_sqlconnection

# Example is taken from http://aiohttp.readthedocs.io/en/stable/#getting-started

import aiohttp

import asyncio

async def fetch(session, url):

async with session.get(url) as response:

return await response.text()

# Client code, provided for reference

async def main():

async with aiohttp.ClientSession() as session:

html = await fetch(session, 'http://python.org')

print(html)

loop = asyncio.get_event_loop()

loop.run_until_complete(main())

import aiohttp

@retry(aiohttp.DisconnectedError, aiohttp.ClientError,

aiohttp.HttpProcessingError)

async def fetch(session, url):

async with session.get(url) as response:

return await response.text()

import logging

from functools import wraps

log = logging.getLogger(__name__)

def retry(*exceptions, retries=3, cooldown=1, verbose=True):

    """Decorate an async function to execute it a few times before giving up.

    Hopes that problem is resolved by another side shortly.

    Args:

        exceptions (Tuple[Exception]) : The exceptions expected during function execution

        retries (int): Number of retries of function execution.

        cooldown (int): Seconds to wait before retry.

        verbose (bool): Specifies if we should log about not successful attempts.

    """

    def wrap(func):

        @wraps(func)

        async def inner(*args, **kwargs):

            retries_count = 0

            while True:

                try:

                    result = await func(*args, **kwargs)

                except exceptions as err:

                    retries_count += 1

                    message = "Exception during {} execution. " \

                              "{} of {} retries attempted".

                              format(func, retries_count, retries)

                    if retries_count > retries:

                        verbose and log.exception(message)

                        raise RetryExhaustedError(

                            func.__qualname__, args, kwargs) from err

                    else:

                        verbose and log.warning(message)

                    if cooldown:

                        await asyncio.sleep(cooldown)

                else:

                    return result

        return inner

    return wrap