Troubleshooting Hanging Requests with Python Requests Library

Feb 3, 2024 ยท 2 min read

The Python Requests library makes sending HTTP requests simple and intuitive. However, sometimes you may encounter issues where Requests seems to hang and never return a response. Here are some things to try when facing hanging requests:

Check for Network/Connectivity Issues

Before diving into application-specific troubleshooting, rule out any network or connectivity problems. Try accessing the target URL from a browser or curl to validate that the server is reachable. Issues like firewalls blocking connections, DNS failures, or server outages can manifest as hanging requests.

Use Timeout Settings

By default, Requests waits indefinitely for a response. Use the timeout parameter to bounds wait times:

import requests

response = requests.get('https://example.com', timeout=3) 

This will raise a Timeout exception if no response starts within 3 seconds. Start with conservative timeouts and increase as needed.

Retry with Exponential Backoff

An overloaded server may return errors or hang under high load. Implementing exponential backoff retries can help recover in these scenarios:

from time import sleep

MAX_RETRIES = 5
TIMEOUT = 1

for i in range(MAX_RETRIES):
  try:
    response = requests.get(url, timeout=TIMEOUT)
    break
  except:
    TIMEOUT *= 2
    sleep(TIMEOUT)

This exponentially increases the timeout after each failure, backing off to give systems time to recover.

Check for Deadlocks or Race Conditions

Application code may also cause requests to hang by introducing threading deadlocks or race conditions. Profile hanging requests using a debugger or logs to check for synchronized code blocks. Refactoring access to shared state can help eliminate these hangs.

With timeouts and retries in place, focus troubleshooting on application factors on the client and server side that could be leading to the stalled requests.

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