test_dbm_gnu.test_reorganize() failed on x86-64 High Sierra 3.x

[vstinner]

BPO	33901
Nosy	@warsaw, @ronaldoussoren, @vstinner, @ned-deily, @serhiy-storchaka, @zhangyangyu, @mattbillenstein, @miss-islington
PRs	Use more specific asserts in dbm tests. #7786 [3.7] Use more specific asserts in dbm tests. (GH-7786) #7787 [3.6] Use more specific asserts in dbm tests. (GH-7786) #7788 bpo-33901: Enhance test_dbm_gnu #7790 bpo-33901: Fix test_dbm_gnu for gdbm 1.15 #7791 bpo-33901: Add _gdbm._GDBM_VERSION #7794 bpo-33901: Better test_dbm_gnu.test_reorganize() fix #7795 [3.7] bpo-33901: Fix test_dbm_gnu for gdbm 1.15 #7798 [3.6] bpo-33901: Fix test_dbm_gnu for gdbm 1.15 (GH-7798) #7801 [2.7] bpo-33901: Fix test_gdbm for gdbm 1.15 (GH-7798) #7818

^{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 = <Date 2018-06-20.08:57:53.912>
created_at = <Date 2018-06-19.08:50:25.277>
labels = ['OS-mac', '3.8', '3.7', 'tests']
title = 'test_dbm_gnu.test_reorganize() failed on x86-64 High Sierra 3.x'
updated_at = <Date 2018-06-20.08:57:53.909>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2018-06-20.08:57:53.909>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-06-20.08:57:53.912>
closer = 'vstinner'
components = ['macOS', 'Tests']
creation = <Date 2018-06-19.08:50:25.277>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 33901
keywords = ['patch']
message_count = 24.0
messages = ['319942', '319951', '319952', '319953', '319954', '319955', '319956', '319957', '319958', '319959', '319960', '319962', '319963', '319964', '319966', '319982', '319983', '319987', '319988', '319998', '319999', '320000', '320038', '320039']
nosy_count = 8.0
nosy_names = ['barry', 'ronaldoussoren', 'vstinner', 'ned.deily', 'serhiy.storchaka', 'xiang.zhang', 'mattbillenstein', 'miss-islington']
pr_nums = ['7786', '7787', '7788', '7790', '7791', '7794', '7795', '7798', '7801', '7818']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue33901'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7', 'Python 3.8']

[vstinner]

http://buildbot.python.org/all/#/builders/145/builds/81

x86-64 High Sierra 3.x:

======================================================================
FAIL: test_reorganize (test.test_dbm_gnu.TestGdbm)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_dbm_gnu.py", line 77, in test_reorganize
    self.assertTrue(size0 < size1)
AssertionError: False is not true

The only change of this build is the commit cb97073: bpo-33630. But I hardly believe that it's related.

[serhiy-storchaka]

New changeset 22525de by Serhiy Storchaka in branch 'master':
Use more specific asserts in dbm tests. (GH-7786)
22525de

[serhiy-storchaka]

http://buildbot.python.org/all/#/builders/145/builds/84

======================================================================
FAIL: test_reorganize (test.test_dbm_gnu.TestGdbm)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_dbm_gnu.py", line 77, in test_reorganize
    self.assertGreater(size1, size0)
AssertionError: 16777216 not greater than 16777216

---

[serhiy-storchaka]

16777216 = 2**24 = 16 MiB

Looks too large for the size of an empty database.

[vstinner]

@matt Billenstein: Hi! Would you mind to have a look at this issue? It seems like test_dbm_gnu started to fail today. Did you upgrade the buildbot worker recently?

[serhiy-storchaka]

For comparison, on Linux size0 = 12288 = 12 KiB. 3 decimal orders smaller.

[vstinner]

size0=16777216 (16 MiB). On my Fedora 28, size0=12288 (12 KiB).

Even more strange: another test starts by removing the filename, just in case!?

    def test_error_conditions(self):
        # Try to open a non-existent database.
        unlink(filename)
        ...

Maybe the setUp() method must fail if filename already exists?

The buildbot runs tests in subprocesses:
"Run tests in parallel using 2 child processes"

regrtest spawns child procsses which creates their own temporary empty current directory and TESTFN is related to the current directory. If the filename/database existed before test_reorganize(), it's likely a bug in test_dbm_gnu: but there is a single TestCase class with a tearDown() method which calls unlink(filename).

--

Maybe x86-64 High Sierra 3.x has a different dbm library version which always creates an empty database with 16 MiB preallocated on disk!?

[vstinner]

Ok, I reproduced the issue on macOS High-Sierra and gdbm 1.15. Creating a DB creates a file of 16 MiB.

macbook:master haypo$ brew info gdbm
gdbm: stable 1.15 (bottled)
GNU database manager
https://www.gnu.org/software/gdbm/
/usr/local/Cellar/gdbm/1.15 (19 files, 569.8KB)
Poured from bottle on 2018-06-19 at 13:48:35
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/gdbm.rb
==> Options
--with-libgdbm-compat
Build libgdbm_compat, a compatibility layer which provides UNIX-like dbm and ndbm interfaces.

and

macbook:master haypo$ ./python.exe
Python 3.8.0a0 (heads/master:22525de, Jun 19 2018, 13:56:57) 
[Clang 9.1.0 (clang-902.0.39.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dbm.gnu
>>> import os
>>> dbm.gnu.open("x", "c").close()
>>> os.path.getsize("x")
16777216

[serhiy-storchaka]

PR 7791 makes the test less useful.

I suggest to replace 10000 with size0 or max(size0, 10000).

[vstinner]

New changeset 1261bfa by Victor Stinner in branch 'master':
bpo-33901: Fix test_dbm_gnu for gdbm 1.15 (GH-7791)
1261bfa

[zhangyangyu]

Considering adding gdbm version to pythoninfo? It is possible to expose version info from gnu dbm.

[serhiy-storchaka]

Did not increasing the size of the value fixed the test?