http - How to implement retry mechanism into python requests library?

Question

I would like to add a retry mechanism to python request library, so scripts that are using it will retry for non fatal errors.

At this moment I do consider three kind of errors to be recoverable:

• HTTP return codes 502, 503, 504
• host not found (less important now)
• request timeout

At the first stage I do want to retry specified 5xx requests every minute.

I want to be able to add this functionality transparently, without having to manually implement recovery for each HTTP call made from inside these scripts or libraries that are using python-requests.

Answer 1

This snippet of code will make all HTTP requests from the same session retry for a total of 5 times, sleeping between retries with an increasing backoff of 0s, 2s, 4s, 8s, 16s (the first retry is done immediately). It will retry on basic connectivity issues (including DNS lookup failures), and HTTP status codes of 502, 503 and 504.

import logging
import requests

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

logging.basicConfig(level=logging.DEBUG)

s = requests.Session()
retries = Retry(total=5, backoff_factor=1, status_forcelist=[ 502, 503, 504 ])
s.mount('http://', HTTPAdapter(max_retries=retries))

s.get("http://httpstat.us/503")

See Retry class for details.