"IOError: [Errno 35] Resource temporarily unavailable" with PhantomJS, python, selenium, unittest

Question

I'm having an issue with running unit tests using selenium and the PhantomJS driver. It seems to be related to resource contention for stderr/stdout in the PhantomJS process. The error is:

$ python -m unittest selenium_failure.SeleniumTestCase
[]
[{u'timestamp': 1395857498698, u'message': u'{"log":{"version":"1.2","creator":{"name":"PhantomJS","version":"1.9.7"},"pages":[{"startedDateTime":"2014-03-26T18:11:38.347Z","id":"https://www.google.com/","title":"Google","pageTimings":{"onLoad":294}}],"entries":[{"startedDateTime":"2014-03-26T18:11:38.344Z","time":127,"request":{"method":"GET","url":"https://www.google.com/","httpVersion":"HTTP/1.1","cookies":[],"headers":[{"name":"User-Agent","value":"Mozilla/5.0 (Macintosh; Intel Mac OS X) AppleWebKit/534.34 (KHTML, like Gecko) PhantomJS/1.9.7 Safari/534.34"},{"name":"Accept","value":"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"}],"queryString":[],"headersSize":-1,"bodySize":-1},"response":{"status":200,"statusText":"OK","httpVersion":"HTTP/1.1","cookies":[],"headers":[{"name":"Date","value":"Wed, 26 Mar 2014 18:11:37 GMT"},{"name":"Expires","value":"-1"},{"name":"Cache-Control","value":"private, max-age=0"},{"name":"Content-Type","value":"text/html; charset=UTF-8"},{"name":"Set-Cookie",E
======================================================================
ERROR: test_that_something_fails (selenium_failure.SeleniumTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "selenium_failure.py", line 16, in test_that_something_fails
    print repr(self.selenium.get_log('har'))
IOError: [Errno 35] Resource temporarily unavailable

----------------------------------------------------------------------
Ran 1 test in 2.398s

FAILED (errors=1)

More detailed gist here: https://gist.github.com/lucaswiman/9788422

import unittest
import logging
from selenium.webdriver import phantomjs
import sys

class SeleniumTestCase(unittest.TestCase):
    def setUp(self):
        self.selenium = phantomjs.webdriver.WebDriver()
    def tearDown(self):
        self.selenium.quit()
    def test_that_something_fails(self):
        self.selenium.get('https://www.google.com')
        print repr(self.selenium.get_log('browser'))
        print repr(self.selenium.get_log('har'))
        raise AssertionError()

The error is reproducible with that gist on OS X, but not on Ubuntu 12.04. I believe it's not specific to OS X, since I've seen a similar error for our integration tests on running on Ubuntu, though I haven't been able to reproduce it in an isolated form.

• Python 2.7.6
• selenium==2.35.0
• phantomjs@1.9.7

Answer 1

Fixed! A coworker pointed me to this related issue: http://trac.edgewall.org/ticket/2066#comment:1 I modified the patch there to make sys.__stderr__ and sys.__stdout__ have the block flag. Calling that function immediately after the instantiation of the phantomjs WebDriver allowed the stderr to be sent to stderr.