test_preload fails with PyPy3: AttributeError: module 'resource' has no attribute 'RUSAGE_THREAD'

[sbraz]

Affected Operating Systems

• Linux

Affected py-lmdb Version

git master

py-lmdb Installation Method

setup.py build

Using bundled or distribution-provided LMDB library?

Both

Distribution name and LMDB library version

Gentoo / v0.9.24

Describe Your Problem

Hi, I've noticed that one test fails with PyPy3:

======================================= test session starts ========================================
platform linux -- Python 3.6.9[pypy-7.3.2-final], pytest-6.1.0, py-1.9.0, pluggy-0.13.1 -- /usr/bin/pypy3
cachedir: .pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('/tmp/py-lmdb/.hypothesis/examples')
rootdir: /tmp/py-lmdb
plugins: hypothesis-5.36.1, requests-mock-1.8.0
collected 1 item                                                                                   

tests/cursor_test.py::PreloadTest::test_preload FAILED                                       [100%]

============================================= FAILURES =============================================
_____________________________________ PreloadTest.test_preload _____________________________________

self = <cursor_test.PreloadTest testMethod=test_preload>

    @unittest.skipIf(sys.platform != 'linux', "test only works on Linux")
    def test_preload(self):
        """
        Test that reading just the key doesn't prefault the value contents, but
        reading the data does.
        """
    
        import resource
        self.c.put(B('a'), B('a') * (256 * 1024 * 1024))
        self.txn.commit()
        self.env.close()
        # Just reading the data is obviously going to fault the value in.  The
        # point is to fault it in while the GIL is unlocked.  We use the buffers
        # API so that we're not actually copying the data in.  This doesn't
        # actually show that we're prefaulting with the GIL unlocked, but it
        # does prove we prefault at all, and in 2 correct places.
        self.path, self.env = testlib.temp_env(path=self.path, writemap=True)
        self.txn = self.env.begin(write=True, buffers=True)
        self.c = self.txn.cursor()
>       minflts_before = resource.getrusage(resource.RUSAGE_THREAD)[6]
E       AttributeError: module 'resource' has no attribute 'RUSAGE_THREAD'

tests/cursor_test.py:267: AttributeError
===================================== short test summary info ======================================
FAILED tests/cursor_test.py::PreloadTest::test_preload - AttributeError: module 'resource' has no...
======================================== 1 failed in 0.54s =========================================

Apparently PyPy3's resource doesn't expose a RUSAGE_THREAD attribute. I checked your CI and the test gets skipped on PyPy2 because sys.platform is linux2 (otherwise it would fail there too because the attribute was added to Python 3.2).

[jnwatson]

Thank you for the info. Do you happen to know an alternative to get the minor fault count?

[jnwatson]

Dup of #248