[Python-checkins] cpython (3.1): #11999: sync based on comparing mtimes, not mtime to system clock
r.david.murray
python-checkins at python.org
Sat May 7 04:27:25 CEST 2011
http://hg.python.org/cpython/rev/252451fef13f
changeset: 69882:252451fef13f
branch: 3.1
parent: 69869:26da299ca88e
user: R David Murray <rdmurray at bitdance.com>
date: Fri May 06 22:07:19 2011 -0400
summary:
#11999: sync based on comparing mtimes, not mtime to system clock
files:
Lib/mailbox.py | 76 ++++++++++++++-------------
Lib/test/test_mailbox.py | 23 +++----
Misc/NEWS | 4 +
3 files changed, 54 insertions(+), 49 deletions(-)
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -224,19 +224,24 @@
def __init__(self, dirname, factory=None, create=True):
"""Initialize a Maildir instance."""
Mailbox.__init__(self, dirname, factory, create)
+ self._paths = {
+ 'tmp': os.path.join(self._path, 'tmp'),
+ 'new': os.path.join(self._path, 'new'),
+ 'cur': os.path.join(self._path, 'cur'),
+ }
if not os.path.exists(self._path):
if create:
os.mkdir(self._path, 0o700)
- os.mkdir(os.path.join(self._path, 'tmp'), 0o700)
- os.mkdir(os.path.join(self._path, 'new'), 0o700)
- os.mkdir(os.path.join(self._path, 'cur'), 0o700)
+ for path in self._paths.values():
+ os.mkdir(path, 0o700)
else:
raise NoSuchMailboxError(self._path)
self._toc = {}
- self._last_read = None # Records last time we read cur/new
- # NOTE: we manually invalidate _last_read each time we do any
- # modifications ourselves, otherwise we might get tripped up by
- # bogus mtime behaviour on some systems (see issue #6896).
+ self._toc_mtimes = {}
+ for subdir in ('cur', 'new'):
+ self._toc_mtimes[subdir] = os.path.getmtime(self._paths[subdir])
+ self._last_read = time.time() # Records last time we read cur/new
+ self._skewfactor = 0.1 # Adjust if os/fs clocks are skewing
def add(self, message):
"""Add message and return assigned key."""
@@ -270,15 +275,11 @@
raise
if isinstance(message, MaildirMessage):
os.utime(dest, (os.path.getatime(dest), message.get_date()))
- # Invalidate cached toc
- self._last_read = None
return uniq
def remove(self, key):
"""Remove the keyed message; raise KeyError if it doesn't exist."""
os.remove(os.path.join(self._path, self._lookup(key)))
- # Invalidate cached toc (only on success)
- self._last_read = None
def discard(self, key):
"""If the keyed message exists, remove it."""
@@ -313,8 +314,6 @@
if isinstance(message, MaildirMessage):
os.utime(new_path, (os.path.getatime(new_path),
message.get_date()))
- # Invalidate cached toc
- self._last_read = None
def get_message(self, key):
"""Return a Message representation or raise a KeyError."""
@@ -370,8 +369,8 @@
def flush(self):
"""Write any pending changes to disk."""
# Maildir changes are always written immediately, so there's nothing
- # to do except invalidate our cached toc.
- self._last_read = None
+ # to do.
+ pass
def lock(self):
"""Lock the mailbox."""
@@ -469,34 +468,39 @@
def _refresh(self):
"""Update table of contents mapping."""
- new_mtime = os.path.getmtime(os.path.join(self._path, 'new'))
- cur_mtime = os.path.getmtime(os.path.join(self._path, 'cur'))
-
- if (self._last_read is not None and
- new_mtime <= self._last_read and cur_mtime <= self._last_read):
- return
-
+ # If it has been less than two seconds since the last _refresh() call,
+ # we have to unconditionally re-read the mailbox just in case it has
+ # been modified, because os.path.mtime() has a 2 sec resolution in the
+ # most common worst case (FAT) and a 1 sec resolution typically. This
+ # results in a few unnecessary re-reads when _refresh() is called
+ # multiple times in that interval, but once the clock ticks over, we
+ # will only re-read as needed. Because the filesystem might be being
+ # served by an independent system with its own clock, we record and
+ # compare with the mtimes from the filesystem. Because the other
+ # system's clock might be skewing relative to our clock, we add an
+ # extra delta to our wait. The default is one tenth second, but is an
+ # instance variable and so can be adjusted if dealing with a
+ # particularly skewed or irregular system.
+ if time.time() - self._last_read > 2 + self._skewfactor:
+ refresh = False
+ for subdir in self._toc_mtimes:
+ mtime = os.path.getmtime(self._paths[subdir])
+ if mtime > self._toc_mtimes[subdir]:
+ refresh = True
+ self._toc_mtimes[subdir] = mtime
+ if not refresh:
+ return
+ # Refresh toc
self._toc = {}
- def update_dir (subdir):
- path = os.path.join(self._path, subdir)
+ for subdir in self._toc_mtimes:
+ path = self._paths[subdir]
for entry in os.listdir(path):
p = os.path.join(path, entry)
if os.path.isdir(p):
continue
uniq = entry.split(self.colon)[0]
self._toc[uniq] = os.path.join(subdir, entry)
-
- update_dir('new')
- update_dir('cur')
-
- # We record the current time - 1sec so that, if _refresh() is called
- # again in the same second, we will always re-read the mailbox
- # just in case it's been modified. (os.path.mtime() only has
- # 1sec resolution.) This results in a few unnecessary re-reads
- # when _refresh() is called multiple times in the same second,
- # but once the clock ticks over, we will only re-read as needed.
- now = int(time.time() - 1)
- self._last_read = time.time() - 1
+ self._last_read = time.time()
def _lookup(self, key):
"""Use TOC to return subpath for given key, or raise a KeyError."""
diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -742,21 +742,18 @@
def test_reread(self):
- # Initially, the mailbox has not been read and the time is null.
- assert getattr(self._box, '_last_read', None) is None
-
- # Refresh mailbox; the times should now be set to something.
- self._box._refresh()
- assert getattr(self._box, '_last_read', None) is not None
-
- # Put the last modified times more than one second into the past
- # (because mtime has a one second granularity, a refresh is done
- # unconditionally if called for within the same second, just in case
- # the mbox has changed).
+ # Put the last modified times more than two seconds into the past
+ # (because mtime may have a two second granularity)
for subdir in ('cur', 'new'):
os.utime(os.path.join(self._box._path, subdir),
(time.time()-5,)*2)
+ # Because mtime has a two second granularity in worst case (FAT), a
+ # refresh is done unconditionally if called for within
+ # two-second-plus-a-bit of the last one, just in case the mbox has
+ # changed; so now we have to wait for that interval to expire.
+ time.sleep(2.01 + self._box._skewfactor)
+
# Re-reading causes the ._toc attribute to be assigned a new dictionary
# object, so we'll check that the ._toc attribute isn't a different
# object.
@@ -765,7 +762,7 @@
return self._box._toc is not orig_toc
self._box._refresh()
- assert not refreshed()
+ self.assertFalse(refreshed())
# Now, write something into cur and remove it. This changes
# the mtime and should cause a re-read.
@@ -774,7 +771,7 @@
f.close()
os.unlink(filename)
self._box._refresh()
- assert refreshed()
+ self.assertTrue(refreshed())
class _TestMboxMMDF(TestMailbox):
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -66,6 +66,10 @@
Library
-------
+- Issue 11999: fixed sporadic sync failure mailbox.Maildir due to its trying to
+ detect mtime changes by comparing to the system clock instead of to the
+ previous value of the mtime.
+
- Issue #10684: shutil.move used to delete a folder on case insensitive
filesystems when the source and destination name where the same except
for the case.
--
Repository URL: http://hg.python.org/cpython
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