Understanding an IOError #3145

P-EB · 2018-01-23T16:21:49Z

Hi,

I'm packaging for debian some pytest extensions. I submitted a bug to pytest-httpbin (see here: kevin1024/pytest-httpbin#47), regarding some issues with their tests.

Yet, I'm also trying to understand what is going south by myself, and for now, I totally fail at it.

Here's an error I got recently while building the package:

=================================== FAILURES ===================================
______________________________ test_unicode_data _______________________________

self = <CallInfo when='call' exception: seek() called during concurrent operation on the same file object>
func = <function <lambda> at 0x7f81adc0df50>, when = 'call'

    def __init__(self, func, when):
        #: context of invocation: one of "setup", "call",
        #: "teardown", "memocollect"
        self.when = when
        self.start = time()
        try:
>           self.result = func()

/usr/lib/python2.7/dist-packages/_pytest/runner.py:196: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python2.7/dist-packages/_pytest/runner.py:182: in <lambda>
    return CallInfo(lambda: ihook(item=item, **kwds), when=when)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:745: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:339: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:334: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:613: in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:250: in _wrapped_call
    wrap_controller.send(call_outcome)
/usr/lib/python2.7/dist-packages/_pytest/capture.py:139: in pytest_runtest_call
    self.suspendcapture_item(item, "call")
/usr/lib/python2.7/dist-packages/_pytest/capture.py:156: in suspendcapture_item
    out, err = self.suspendcapture(in_=in_)
/usr/lib/python2.7/dist-packages/_pytest/capture.py:97: in suspendcapture
    outerr = cap.readouterr()
/usr/lib/python2.7/dist-packages/_pytest/capture.py:327: in readouterr
    self.err.snap() if self.err is not None else "")
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <FDCapture 2 oldfd=6>

    def snap(self):
        f = self.tmpfile
>       f.seek(0)
E       IOError: seek() called during concurrent operation on the same file object

/usr/lib/python2.7/dist-packages/_pytest/capture.py:375: IOError
--------------------------- Captured stderr teardown ---------------------------
127.0.0.1 - - [23/Jan/2018 16:13:00] "POST /post HTTP/1.1" 200 477

The full test log is here:


autopkgtest /home/peb/git/debian/pytest-httpbin/pytest-httpbin_0.3.0-1_amd64.changes -- schroot unstable-amd64-sbuild; aptexit=$?; if test $aptexit = 8 -o $aptexit = 12; then exit 0; else exit $aptexit; fi
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

autopkgtest [17:12:47]: version 4.4
autopkgtest [17:12:47]: host pimeys; command line: /usr/bin/autopkgtest /home/peb/git/debian/pytest-httpbin/pytest-httpbin_0.3.0-1_amd64.changes -- schroot unstable-amd64-sbuild
autopkgtest [17:12:47]: testbed dpkg architecture: amd64
autopkgtest [17:12:47]: testbed running kernel: Linux 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2 (2017-06-12)
autopkgtest [17:12:47]: @@@@@@@@@@@@@@@@@@@@ source /home/peb/git/debian/pytest-httpbin/pytest-httpbin_0.3.0-1.dsc
dpkg-source: warning: extracting unsigned source package (/tmp/autopkgtest.ge1fix/pytest-httpbin_0.3.0-1.dsc)
dpkg-source: info: extracting pytest-httpbin in pytest-httpbin-0.3.0
dpkg-source: info: unpacking pytest-httpbin_0.3.0.orig.tar.gz
dpkg-source: info: unpacking pytest-httpbin_0.3.0-1.debian.tar.xz
dpkg-source: info: applying 0001-Uses-context-manager-for-requests.Session.patch
autopkgtest [17:12:48]: testing package pytest-httpbin version 0.3.0-1
autopkgtest [17:12:48]: build not needed
autopkgtest [17:12:48]: test python-pytest-httpbin: preparing testbed
Get:1 file:/tmp/autopkgtest.ge1fix/binaries  InRelease
Ign:1 file:/tmp/autopkgtest.ge1fix/binaries  InRelease
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Get:3 file:/tmp/autopkgtest.ge1fix/binaries  Release.gpg
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Get:4 file:/tmp/autopkgtest.ge1fix/binaries  Packages [2302 B]
Reading package lists...
Reading package lists...
Building dependency tree...
Reading state information...
Correcting dependencies...Starting pkgProblemResolver with broken count: 0
Starting 2 pkgProblemResolver with broken count: 0
Done
 Done
Starting pkgProblemResolver with broken count: 0
Starting 2 pkgProblemResolver with broken count: 0
Done
The following additional packages will be installed:
  ca-certificates libexpat1 libjs-jquery libpython-stdlib libpython2.7-minimal
  libpython2.7-stdlib libssl1.1 mime-support openssl python python-all
  python-certifi python-chardet python-click python-colorama python-decorator
  python-flask python-gevent python-greenlet python-httpbin python-idna
  python-itsdangerous python-jinja2 python-markupsafe python-minimal
  python-pkg-resources python-py python-pytest python-pytest-httpbin
  python-requests python-six python-urllib3 python-werkzeug python2.7
  python2.7-minimal
Suggested packages:
  python-doc python-tk python-flask-doc python-gevent-doc python-gevent-dbg
  python-openssl python-greenlet-doc python-greenlet-dev python-greenlet-dbg
  python-jinja2-doc python-setuptools subversion python-pytest-xdist
  python-mock python-cryptography python-socks python-ntlm ipython
  python-genshi python-lxml python-redis python-pylibmc | python-memcache
  python-termcolor python-watchdog python-werkzeug-doc python2.7-doc
  binfmt-support
Recommended packages:
  javascript-common file python-blinker gunicorn python-simplejson
  python-cryptography python-ipaddress python-openssl python-pyinotify
The following NEW packages will be installed:
  ca-certificates libexpat1 libjs-jquery libpython-stdlib libpython2.7-minimal
  libpython2.7-stdlib libssl1.1 mime-support openssl python python-all
  python-certifi python-chardet python-click python-colorama python-decorator
  python-flask python-gevent python-greenlet python-httpbin python-idna
  python-itsdangerous python-jinja2 python-markupsafe python-minimal
  python-pkg-resources python-py python-pytest python-pytest-httpbin
  python-requests python-six python-urllib3 python-werkzeug python2.7
  python2.7-minimal
0 upgraded, 35 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
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Get:27 http://cdn-fastly.deb.debian.org/debian unstable/main amd64 python-httpbin all 0.5.0+dfsg-2 [81.1 kB]
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Get:34 http://cdn-fastly.deb.debian.org/debian unstable/main amd64 python-urllib3 all 1.22-1 [97.7 kB]
Get:35 http://cdn-fastly.deb.debian.org/debian unstable/main amd64 python-requests all 2.18.4-1 [77.2 kB]
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autopkgtest [17:13:00]: test python-pytest-httpbin: [-----------------------
[*] testing on python2.7:
pytest_httpbin/plugin.py:4: ImportWarning: Not importing directory 'pytest_httpbin/certs': missing __init__.py
  from . import serve, certs
============================= test session starts ==============================
platform linux2 -- Python 2.7.14+, pytest-3.2.1, py-1.4.34, pluggy-0.4.0 -- /usr/bin/python2.7
cachedir: .cache
rootdir: /tmp/autopkgtest.ge1fix/build.OUu/pytest-httpbin-0.3.0, inifile:
plugins: httpbin-0.3.0
collecting ... collected 19 items

tests/test_httpbin.py::test_httpbin_gets_injected PASSED
tests/test_httpbin.py::test_httpbin_accepts_get_requests PASSED
tests/test_httpbin.py::test_httpbin_secure_accepts_get_requests PASSED
tests/test_httpbin.py::test_httpbin_secure_accepts_lots_of_get_requests PASSED
tests/test_httpbin.py::test_httpbin_accepts_lots_of_get_requests_in_single_session PASSED
tests/test_httpbin.py::test_httpbin_both[http] PASSED
tests/test_httpbin.py::test_chunked_encoding[http] PASSED
tests/test_httpbin.py::test_httpbin_both[https] PASSED
tests/test_httpbin.py::test_chunked_encoding[https] PASSED
tests/test_httpbin.py::test_httpbin_join PASSED
tests/test_httpbin.py::test_httpbin_str PASSED
tests/test_httpbin.py::TestClassBassedTests::test_http PASSED
tests/test_httpbin.py::TestClassBassedTests::test_http_secure PASSED
tests/test_server.py::test_content_type_header_not_automatically_added PASSED
tests/test_server.py::test_unicode_data FAILED

=================================== FAILURES ===================================
______________________________ test_unicode_data _______________________________

self = <CallInfo when='call' exception: seek() called during concurrent operation on the same file object>
func = <function <lambda> at 0x7f81adc0df50>, when = 'call'

    def __init__(self, func, when):
        #: context of invocation: one of "setup", "call",
        #: "teardown", "memocollect"
        self.when = when
        self.start = time()
        try:
>           self.result = func()

/usr/lib/python2.7/dist-packages/_pytest/runner.py:196: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python2.7/dist-packages/_pytest/runner.py:182: in <lambda>
    return CallInfo(lambda: ihook(item=item, **kwds), when=when)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:745: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:339: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:334: in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:613: in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
/usr/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py:250: in _wrapped_call
    wrap_controller.send(call_outcome)
/usr/lib/python2.7/dist-packages/_pytest/capture.py:139: in pytest_runtest_call
    self.suspendcapture_item(item, "call")
/usr/lib/python2.7/dist-packages/_pytest/capture.py:156: in suspendcapture_item
    out, err = self.suspendcapture(in_=in_)
/usr/lib/python2.7/dist-packages/_pytest/capture.py:97: in suspendcapture
    outerr = cap.readouterr()
/usr/lib/python2.7/dist-packages/_pytest/capture.py:327: in readouterr
    self.err.snap() if self.err is not None else "")
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <FDCapture 2 oldfd=6>

    def snap(self):
        f = self.tmpfile
>       f.seek(0)
E       IOError: seek() called during concurrent operation on the same file object

/usr/lib/python2.7/dist-packages/_pytest/capture.py:375: IOError
--------------------------- Captured stderr teardown ---------------------------
127.0.0.1 - - [23/Jan/2018 16:13:00] "POST /post HTTP/1.1" 200 477

As you can see, we use pytest version 3.2.1.

Can you help me to understand where the unsafe "seek" comes from? My guess is that there is an error during the test, and that when pytest tries to capture the stderr, it does a seek but fails as stderr has been closed or something else. So my goal would be to get rid of this error and understand then what is actually not going well?

Thanks!

The text was updated successfully, but these errors were encountered:

nicoddemus · 2018-01-23T19:56:30Z

Seems similar to #2370, at least the symptom. Can you try passing -s to pytest to see if the problem goes away?

P-EB · 2018-01-24T11:34:05Z

I'll give it a try.

Thanks

P-EB · 2018-01-24T11:39:26Z

I'll have to run the packaging multiple times as it's non-deterministic, maybe it'll take a while.

Sorry for the randomness. :(

P-EB · 2018-01-24T12:17:30Z

16 builds passed without any error.

What are the cons of the -s option if any?

nicoddemus · 2018-01-24T12:38:04Z

-s only disables stdout/stderr capturing, the only downside is that print() and writes to stdout/stderr will appear in the middle of the test run, nothing critical really.

P-EB · 2018-01-24T13:03:25Z

That's fine with me. I think you solved all my issues. Thanks!

I'll leave it open for a little while (let's say a week), and come back at you if I see anything relevant.

Cheers!

P-EB · 2018-01-24T14:03:17Z

@nicoddemus maybe you should remove the bug tag? :)

nicoddemus · 2018-01-24T14:06:47Z

I'll leave it open for a little while (let's say a week), and come back at you if I see anything relevant.

If you don't mind I will close this for now, and we can re-open if you see anything relevant that demands some action on pytest's side. 👍

maybe you should remove the bug tag? :)

Yep thanks 😁

pytestbot added the type: bug problem that needs to be addressed label Jan 23, 2018

nicoddemus added type: question general question, might be closed after 2 weeks of inactivity and removed type: bug problem that needs to be addressed labels Jan 24, 2018

nicoddemus closed this as completed Jan 24, 2018

pytestbot mentioned this issue Apr 20, 2018

[docs] understanding input type of e.g. pytest_runtest_setup #3414

Closed

coderabbitai bot mentioned this issue Apr 5, 2025

Test Korbit karthik-H/vigilant-robot#3

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Understanding an IOError #3145

Understanding an IOError #3145

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Understanding an IOError #3145

Understanding an IOError #3145

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