Retry Strategy Misconfigured

7 Dec 2025

1 min read

Retry strategy misconfigured

$ python -c "import requests; from requests.adapters import HTTPAdapter; from urllib3.util.retry import Retry; s=requests.Session(); s.mount('https://', HTTPAdapter(max_retries=Retry(total='x'))); s.get('https://example.com')"
Traceback (most recent call last):
  ...
TypeError: cannot concatenate 'str' and 'int'

Why this happens

Retry.total must be int; wrong retryable methods/status codes can disable retries.

Fix

Configure Retry with correct types and backoff.

Wrong code

from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry
import requests
s = requests.Session()
s.mount('https://', HTTPAdapter(max_retries=Retry(total='3')))

Fixed code

from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry
import requests
s = requests.Session()
retry = Retry(total=3, backoff_factor=0.5, status_forcelist=[429, 500, 502, 503, 504])
s.mount('https://', HTTPAdapter(max_retries=retry))