How to deal with sporadic BadStatusLine, CannotSendRequest errors in python WebDriver

Question

Since we started running selenium UI tests in jenkins, we noticed a small but annoying frequency of errors during tests. We get BadStatusLine and CannotSendRequest errors on seemingly random selenium actions (click, quit, visit, etc.). They would usually look something like: ``` File "/usr/lib/python2.7/unittest/case.py", line 327, in run testMethod() File "/home/jenkins/workspace/Create and Upload Functional Testing/shapeways/test_suite/Portal/CreateAndUpload/TestUploadWhenNotLoggedIn_ExpectLoginModal.py", line 22, in runTest self.dw.visit(ShapewaysUrlBuilder.build_model_upload_url()) File "/home/jenkins/workspace/Create and Upload Functional Testing/webdriver/webdriverwrapper/WebDriverWrapper.py", line 212, in visit return self.execute_and_handle_webdriver_exceptions(lambda: _visit(url)) File "/home/jenkins/workspace/Create and Upload Functional Testing/webdriver/webdriverwrapper/WebDriverWrapper.py", line 887, in execute_and_handle_webdriver_exceptions return function_to_execute()…

Accepted Answer

For a while, I had no repro and no idea what the cause was. I was finally able to repro by running:

```
import requests
import json

while True:

requests.post('http://127.0.0.1/hub/session/', data=json.dumps({"url": "http://example.com/login", "sessionId": "ab64574a-4a17-447a-b2e8-5b0f5ed5e923"}))
```

While this was running, I quit the browser and got a BadStatusLine error! When I tried making that request again, that's when I got the expected "ConnectionError" that you would see from any dead server.

SO, what I suspect happens is that when the browser is sent the kill signal, there is a short window during its shutdown where any response will still be returned but with 0 bytes. That's why you get different types of exceptions for essentially the same problem (browser dies). Turns out we had a cron which was killing our browsers in the background.

How to deal with sporadic BadStatusLine, CannotSendRequest errors in python WebDriver

Solution

Problem