test_logging hangs if /etc/hosts only aliases "localhost" to ::1

[phantal]

BPO	29272
Nosy	@vstinner, @KMiNT21

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-01-14.01:37:00.339>
labels = ['type-bug', 'tests']
title = 'test_logging hangs if /etc/hosts only aliases "localhost" to ::1'
updated_at = <Date 2018-07-02.13:32:07.214>
user = 'https://bugs.python.org/phantal'

bugs.python.org fields:

activity = <Date 2018-07-02.13:32:07.214>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Tests']
creation = <Date 2017-01-14.01:37:00.339>
creator = 'phantal'
dependencies = []
files = []
hgrepos = []
issue_num = 29272
keywords = []
message_count = 3.0
messages = ['285452', '318266', '320881']
nosy_count = 3.0
nosy_names = ['vstinner', 'phantal', 'KMiNT21']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29272'
versions = ['Python 3.6']

Linked PRs

• gh-73458: Fix logging.config.listen() on a host without an IPv4 address #154491

[phantal]

On some of the linux boxes on our (air-gapped, if that matters) network it looks like some of them were mis-configured and their /etc/hosts file looks something like this:

$ cat /etc/hosts
127.0.0.1 snoopy.the.internal.domain snoopy localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

... whereas for other linux machines not exhibiting this problem:

$ cat /etc/hosts
127.0.0.1 woodstock.the.internal.domain woodstock localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

It appears this is causing test_logging to hang while running SocketHandlerTest.

Unfortunately I don't have administrative privileges so I'm not able to prove I'm right. I only have circumstantial evidence, but no machine I tested (about 20 machines) contradicts what I stated above.

[KMiNT21]

The same bug for me:
3.6.5 and 3.6.4 -hangs on test_logging forever.

Thanks to this report - I've commented some lines in /etc/host
and after 'test_logging' passed OK!

[vstinner]

I confirm the issue. test_logging hangs if the resolution of the hostname fails with a timeout.

I worked again the issue by adding my hostname to /etc/hosts.

[serhiy-storchaka]

Should be fixed by #154491.