mirror of https://github.com/python/cpython
#11999: sync based on comparing mtimes, not mtime to system clock
This commit is contained in:
R David Murray
commit
94b8ee3bff
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@ -258,19 +258,24 @@ class Maildir(Mailbox):
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def __init__(self, dirname, factory=None, create=True):
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"""Initialize a Maildir instance."""
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Mailbox.__init__(self, dirname, factory, create)
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self._paths = {
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'tmp': os.path.join(self._path, 'tmp'),
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'new': os.path.join(self._path, 'new'),
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'cur': os.path.join(self._path, 'cur'),
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}
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if not os.path.exists(self._path):
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if create:
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os.mkdir(self._path, 0o700)
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os.mkdir(os.path.join(self._path, 'tmp'), 0o700)
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os.mkdir(os.path.join(self._path, 'new'), 0o700)
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os.mkdir(os.path.join(self._path, 'cur'), 0o700)
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for path in self._paths.values():
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os.mkdir(path, 0o700)
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else:
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raise NoSuchMailboxError(self._path)
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self._toc = {}
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self._last_read = None # Records last time we read cur/new
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# NOTE: we manually invalidate _last_read each time we do any
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# modifications ourselves, otherwise we might get tripped up by
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# bogus mtime behaviour on some systems (see issue #6896).
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self._toc_mtimes = {}
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for subdir in ('cur', 'new'):
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self._toc_mtimes[subdir] = os.path.getmtime(self._paths[subdir])
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self._last_read = time.time() # Records last time we read cur/new
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self._skewfactor = 0.1 # Adjust if os/fs clocks are skewing
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def add(self, message):
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"""Add message and return assigned key."""
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@ -307,15 +312,11 @@ class Maildir(Mailbox):
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raise
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if isinstance(message, MaildirMessage):
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os.utime(dest, (os.path.getatime(dest), message.get_date()))
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# Invalidate cached toc
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self._last_read = None
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return uniq
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def remove(self, key):
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"""Remove the keyed message; raise KeyError if it doesn't exist."""
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os.remove(os.path.join(self._path, self._lookup(key)))
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# Invalidate cached toc (only on success)
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self._last_read = None
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def discard(self, key):
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"""If the keyed message exists, remove it."""
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@ -350,8 +351,6 @@ class Maildir(Mailbox):
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if isinstance(message, MaildirMessage):
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os.utime(new_path, (os.path.getatime(new_path),
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message.get_date()))
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# Invalidate cached toc
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self._last_read = None
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def get_message(self, key):
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"""Return a Message representation or raise a KeyError."""
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@ -407,8 +406,8 @@ class Maildir(Mailbox):
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def flush(self):
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"""Write any pending changes to disk."""
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# Maildir changes are always written immediately, so there's nothing
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# to do except invalidate our cached toc.
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self._last_read = None
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# to do.
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pass
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def lock(self):
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"""Lock the mailbox."""
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@ -506,36 +505,39 @@ class Maildir(Mailbox):
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def _refresh(self):
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"""Update table of contents mapping."""
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if self._last_read is not None:
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for subdir in ('new', 'cur'):
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mtime = os.path.getmtime(os.path.join(self._path, subdir))
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if mtime > self._last_read:
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break
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else:
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# If it has been less than two seconds since the last _refresh() call,
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# we have to unconditionally re-read the mailbox just in case it has
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# been modified, because os.path.mtime() has a 2 sec resolution in the
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# most common worst case (FAT) and a 1 sec resolution typically. This
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# results in a few unnecessary re-reads when _refresh() is called
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# multiple times in that interval, but once the clock ticks over, we
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# will only re-read as needed. Because the filesystem might be being
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# served by an independent system with its own clock, we record and
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# compare with the mtimes from the filesystem. Because the other
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# system's clock might be skewing relative to our clock, we add an
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# extra delta to our wait. The default is one tenth second, but is an
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# instance variable and so can be adjusted if dealing with a
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# particularly skewed or irregular system.
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if time.time() - self._last_read > 2 + self._skewfactor:
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refresh = False
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for subdir in self._toc_mtimes:
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mtime = os.path.getmtime(self._paths[subdir])
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if mtime > self._toc_mtimes[subdir]:
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refresh = True
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self._toc_mtimes[subdir] = mtime
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if not refresh:
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return
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# We record the current time - 1sec so that, if _refresh() is called
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# again in the same second, we will always re-read the mailbox
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# just in case it's been modified. (os.path.mtime() only has
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# 1sec resolution.) This results in a few unnecessary re-reads
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# when _refresh() is called multiple times in the same second,
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# but once the clock ticks over, we will only re-read as needed.
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now = time.time() - 1
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# Refresh toc
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self._toc = {}
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def update_dir (subdir):
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path = os.path.join(self._path, subdir)
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for subdir in self._toc_mtimes:
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path = self._paths[subdir]
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for entry in os.listdir(path):
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p = os.path.join(path, entry)
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if os.path.isdir(p):
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continue
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uniq = entry.split(self.colon)[0]
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self._toc[uniq] = os.path.join(subdir, entry)
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update_dir('new')
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update_dir('cur')
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self._last_read = now
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self._last_read = time.time()
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def _lookup(self, key):
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"""Use TOC to return subpath for given key, or raise a KeyError."""
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@ -870,21 +870,18 @@ class TestMaildir(TestMailbox):
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def test_reread(self):
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# Initially, the mailbox has not been read and the time is null.
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assert getattr(self._box, '_last_read', None) is None
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# Refresh mailbox; the times should now be set to something.
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self._box._refresh()
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assert getattr(self._box, '_last_read', None) is not None
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# Put the last modified times more than one second into the past
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# (because mtime has a one second granularity, a refresh is done
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# unconditionally if called for within the same second, just in case
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# the mbox has changed).
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# Put the last modified times more than two seconds into the past
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# (because mtime may have a two second granularity)
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for subdir in ('cur', 'new'):
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os.utime(os.path.join(self._box._path, subdir),
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(time.time()-5,)*2)
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# Because mtime has a two second granularity in worst case (FAT), a
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# refresh is done unconditionally if called for within
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# two-second-plus-a-bit of the last one, just in case the mbox has
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# changed; so now we have to wait for that interval to expire.
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time.sleep(2.01 + self._box._skewfactor)
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# Re-reading causes the ._toc attribute to be assigned a new dictionary
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# object, so we'll check that the ._toc attribute isn't a different
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# object.
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@ -893,7 +890,7 @@ class TestMaildir(TestMailbox):
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return self._box._toc is not orig_toc
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self._box._refresh()
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assert not refreshed()
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self.assertFalse(refreshed())
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# Now, write something into cur and remove it. This changes
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# the mtime and should cause a re-read.
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@ -902,7 +899,7 @@ class TestMaildir(TestMailbox):
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f.close()
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os.unlink(filename)
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self._box._refresh()
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assert refreshed()
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self.assertTrue(refreshed())
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class _TestMboxMMDF(TestMailbox):
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@ -83,6 +83,10 @@ Core and Builtins
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Library
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-------
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- Issue 11999: fixed sporadic sync failure mailbox.Maildir due to its trying to
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detect mtime changes by comparing to the system clock instead of to the
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previous value of the mtime.
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- ntpath.samefile failed to notice that "a.txt" and "A.TXT" refer to the same
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file on Windows XP. As noticed in issue #10684.
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