Add retry strategy in client side

[Zhaoyilunnn]

Due to the stability issue of backend server, long running VQA programs still face high possibility of failure even if we send tasks asynchronously.

A potential implementation method may leverage urllib3 Retry

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

def requests_retry_session(
    retries=3,
    backoff_factor=0.3,
    status_forcelist=(500, 502, 504),
    session=None,
):
    session = session or requests.Session()
    retry = Retry(
        total=retries,
        read=retries,
        connect=retries,
        backoff_factor=backoff_factor,
        status_forcelist=status_forcelist,
        method_whitelist=["HEAD", "GET", "PUT", "DELETE", "OPTIONS", "TRACE"]
    )
    adapter = HTTPAdapter(max_retries=retry)
    session.mount('http://', adapter)
    session.mount('https://', adapter)
    return session

if __name__ == "__main__":
    url = 'http://httpbin.org/status/500'  
    session = requests_retry_session()
    try:
        response = session.get(url)
        print(response.status_code)
    except Exception as x:
        print('It failed :(', x.__class__.__name__)
    else:
        print('It eventually worked', response.status_code)