Issues with subprocess in Linux (Travis)
Closed this issue · 8 comments
In an effort to make a dtm test (in mooray as it uses pytest...) a problem with subprocess in Travis is seen. The following code works fine locally (Windows):
def test_homepage_ping(execute_task):
response = execute_task(command='ping www.sevanssp.com', path=getcwd(), shell=True, pipe=True)
assert response['returncode'] == 0, print(response)
assert 'ping' in response['output'].lower(), print(response)
assert '194.63.249.212' in response['output'], print(response)
This does not work in Travis. Further investigation shows that shell=True freezes the testing completely. timeout=120 has no effect. Without shell=True the command doesn't work in Linux.
shell=True on Linux
There are differences on Windows and Linux OS whether commands like ping and others can be executed directly or needs to passed through a shell. That's just how it is.
Stalling build
That is strange. Did you manage to capture the piped stdout? I hope that will give a clue to what is going on.
No, the stall gives no feedback. Travis stops it when it has been idle for 10 minutes. shell=False gives FileNotFoundError, as expected.
I suggest you rewrite the test to unittest format in dtm, so we can investigate (and so we can learn how this test looks in unittest format)
Sure, I'll do that.
Have you tried another command like ls?
I've only tested ping www.sevanssp.com. But I've detached subprocess from execute_task and gotten the same result. so the error is not in execute_task
Hmmm. Can it be that some commands like ping are not allowed or that requesting www. redirects to https:\ and that for some reason this causes a stall?
try ping https:\\sevanssp.com
'ping -c 4 www.sevanssp.com' works in linux
It would be good to understand why it is not possible to send this command as a list or tuple, though...
Basically you should pass a sequence (list/tuple) with shell=False and a string with shell=True. It’s because of how Python creates the new processes and send them information, which differs on Windows and Linux.
On Windows you can pass either a string or a sequence since Python interprets the sequence of arguments into a string anyway with shell=False. With shell=True the string is sent directly to the shell.
The same thing happens on Linux with shell=True. However, if a sequence is passed, it is sent as positional arguments to the shell not to the command (first item in the sequence).
Issue logged as #5