lock transactions: fix non-transactional writes
Lock transactions were actually writing *after* the lock was
released. The code was looking at the result of `release_write()` before
writing, then writing based on whether the lock was released. This is
pretty obviously wrong.
- [x] Refactor `Lock` so that a release function can be passed to the
`Lock` and called *only* when a lock is really released.
- [x] Refactor `LockTransaction` classes to use the release function
instead of checking the return value of `release_read()` / `release_write()`
This commit is contained in:
Todd Gamblin
parent
a85b9070cb
commit
98577e3af5
4 changed files with 289 additions and 176 deletions
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@ -95,10 +95,6 @@ def _lock(self, op, timeout=None):
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The lock is implemented as a spin lock using a nonblocking call
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to ``lockf()``.
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On acquiring an exclusive lock, the lock writes this process's
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pid and host to the lock file, in case the holding process needs
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to be killed later.
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If the lock times out, it raises a ``LockError``. If the lock is
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successfully acquired, the total wait time and the number of attempts
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is returned.
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@ -284,11 +280,19 @@ def acquire_write(self, timeout=None):
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self._writes += 1
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return False
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def release_read(self):
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def release_read(self, release_fn=None):
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"""Releases a read lock.
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Returns True if the last recursive lock was released, False if
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there are still outstanding locks.
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Arguments:
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release_fn (callable): function to call *before* the last recursive
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lock (read or write) is released.
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If the last recursive lock will be released, then this will call
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release_fn and return its result (if provided), or return True
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(if release_fn was not provided).
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Otherwise, we are still nested inside some other lock, so do not
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call the release_fn and, return False.
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Does limited correctness checking: if a read lock is released
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when none are held, this will raise an assertion error.
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@ -300,18 +304,30 @@ def release_read(self):
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self._debug(
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'READ LOCK: {0.path}[{0._start}:{0._length}] [Released]'
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.format(self))
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result = True
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if release_fn is not None:
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result = release_fn()
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self._unlock() # can raise LockError.
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self._reads -= 1
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return True
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return result
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else:
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self._reads -= 1
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return False
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def release_write(self):
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def release_write(self, release_fn=None):
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"""Releases a write lock.
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Returns True if the last recursive lock was released, False if
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there are still outstanding locks.
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Arguments:
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release_fn (callable): function to call before the last recursive
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write is released.
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If the last recursive *write* lock will be released, then this
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will call release_fn and return its result (if provided), or
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return True (if release_fn was not provided). Otherwise, we are
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still nested inside some other write lock, so do not call the
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release_fn, and return False.
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Does limited correctness checking: if a read lock is released
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when none are held, this will raise an assertion error.
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@ -323,9 +339,16 @@ def release_write(self):
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self._debug(
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'WRITE LOCK: {0.path}[{0._start}:{0._length}] [Released]'
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.format(self))
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# we need to call release_fn before releasing the lock
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result = True
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if release_fn is not None:
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result = release_fn()
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self._unlock() # can raise LockError.
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self._writes -= 1
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return True
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return result
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else:
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self._writes -= 1
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return False
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@ -349,28 +372,36 @@ def _acquired_debug(self, lock_type, wait_time, nattempts):
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class LockTransaction(object):
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"""Simple nested transaction context manager that uses a file lock.
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This class can trigger actions when the lock is acquired for the
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first time and released for the last.
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Arguments:
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lock (Lock): underlying lock for this transaction to be accquired on
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enter and released on exit
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acquire (callable or contextmanager): function to be called after lock
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is acquired, or contextmanager to enter after acquire and leave
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before release.
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release (callable): function to be called before release. If
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``acquire`` is a contextmanager, this will be called *after*
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exiting the nexted context and before the lock is released.
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timeout (float): number of seconds to set for the timeout when
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accquiring the lock (default no timeout)
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If the ``acquire_fn`` returns a value, it is used as the return value for
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``__enter__``, allowing it to be passed as the ``as`` argument of a
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``with`` statement.
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If ``acquire_fn`` returns a context manager, *its* ``__enter__`` function
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will be called in ``__enter__`` after ``acquire_fn``, and its ``__exit__``
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funciton will be called before ``release_fn`` in ``__exit__``, allowing you
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to nest a context manager to be used along with the lock.
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will be called after the lock is acquired, and its ``__exit__`` funciton
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will be called before ``release_fn`` in ``__exit__``, allowing you to
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nest a context manager inside this one.
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Timeout for lock is customizable.
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"""
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def __init__(self, lock, acquire_fn=None, release_fn=None,
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timeout=None):
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def __init__(self, lock, acquire=None, release=None, timeout=None):
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self._lock = lock
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self._timeout = timeout
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self._acquire_fn = acquire_fn
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self._release_fn = release_fn
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self._acquire_fn = acquire
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self._release_fn = release
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self._as = None
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def __enter__(self):
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@ -383,13 +414,18 @@ def __enter__(self):
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def __exit__(self, type, value, traceback):
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suppress = False
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if self._exit():
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if self._as and hasattr(self._as, '__exit__'):
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if self._as.__exit__(type, value, traceback):
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suppress = True
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if self._release_fn:
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if self._release_fn(type, value, traceback):
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suppress = True
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def release_fn():
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if self._release_fn is not None:
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return self._release_fn(type, value, traceback)
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if self._as and hasattr(self._as, '__exit__'):
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if self._as.__exit__(type, value, traceback):
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suppress = True
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if self._exit(release_fn):
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suppress = True
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return suppress
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@ -398,8 +434,8 @@ class ReadTransaction(LockTransaction):
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def _enter(self):
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return self._lock.acquire_read(self._timeout)
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def _exit(self):
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return self._lock.release_read()
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def _exit(self, release_fn):
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return self._lock.release_read(release_fn)
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class WriteTransaction(LockTransaction):
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@ -407,8 +443,8 @@ class WriteTransaction(LockTransaction):
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def _enter(self):
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return self._lock.acquire_write(self._timeout)
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def _exit(self):
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return self._lock.release_write()
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def _exit(self, release_fn):
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return self._lock.release_write(release_fn)
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class LockError(Exception):
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@ -332,11 +332,12 @@ def __init__(self, root, db_dir=None, upstream_dbs=None,
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def write_transaction(self):
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"""Get a write lock context manager for use in a `with` block."""
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return WriteTransaction(self.lock, self._read, self._write)
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return WriteTransaction(
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self.lock, acquire=self._read, release=self._write)
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def read_transaction(self):
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"""Get a read lock context manager for use in a `with` block."""
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return ReadTransaction(self.lock, self._read)
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return ReadTransaction(self.lock, acquire=self._read)
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def prefix_lock(self, spec):
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"""Get a lock on a particular spec's installation directory.
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@ -624,7 +625,7 @@ def _read_suppress_error():
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self._data = {}
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transaction = WriteTransaction(
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self.lock, _read_suppress_error, self._write
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self.lock, acquire=_read_suppress_error, release=self._write
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)
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with transaction:
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@ -42,6 +42,7 @@
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actually on a shared filesystem.
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"""
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import collections
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import os
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import socket
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import shutil
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@ -776,189 +777,258 @@ def p3(barrier):
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multiproc_test(p1, p2, p3)
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def test_transaction(lock_path):
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class AssertLock(lk.Lock):
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"""Test lock class that marks acquire/release events."""
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def __init__(self, lock_path, vals):
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super(AssertLock, self).__init__(lock_path)
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self.vals = vals
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def acquire_read(self, timeout=None):
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self.assert_acquire_read()
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result = super(AssertLock, self).acquire_read(timeout)
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self.vals['acquired_read'] = True
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return result
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def acquire_write(self, timeout=None):
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self.assert_acquire_write()
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result = super(AssertLock, self).acquire_write(timeout)
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self.vals['acquired_write'] = True
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return result
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def release_read(self, release_fn=None):
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self.assert_release_read()
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result = super(AssertLock, self).release_read(release_fn)
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self.vals['released_read'] = True
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return result
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def release_write(self, release_fn=None):
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self.assert_release_write()
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result = super(AssertLock, self).release_write(release_fn)
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self.vals['released_write'] = True
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return result
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@pytest.mark.parametrize(
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"transaction,type",
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[(lk.ReadTransaction, "read"), (lk.WriteTransaction, "write")]
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)
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def test_transaction(lock_path, transaction, type):
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class MockLock(AssertLock):
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def assert_acquire_read(self):
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assert not vals['entered_fn']
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assert not vals['exited_fn']
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def assert_release_read(self):
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assert vals['entered_fn']
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assert not vals['exited_fn']
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def assert_acquire_write(self):
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assert not vals['entered_fn']
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assert not vals['exited_fn']
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def assert_release_write(self):
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assert vals['entered_fn']
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assert not vals['exited_fn']
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def enter_fn():
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vals['entered'] = True
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# assert enter_fn is called while lock is held
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assert vals['acquired_%s' % type]
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vals['entered_fn'] = True
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def exit_fn(t, v, tb):
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vals['exited'] = True
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# assert exit_fn is called while lock is held
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assert not vals['released_%s' % type]
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vals['exited_fn'] = True
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vals['exception'] = (t or v or tb)
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lock = lk.Lock(lock_path)
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vals = {'entered': False, 'exited': False, 'exception': False}
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with lk.ReadTransaction(lock, enter_fn, exit_fn):
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pass
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vals = collections.defaultdict(lambda: False)
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lock = MockLock(lock_path, vals)
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assert vals['entered']
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assert vals['exited']
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assert not vals['exception']
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with transaction(lock, acquire=enter_fn, release=exit_fn):
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assert vals['acquired_%s' % type]
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assert not vals['released_%s' % type]
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vals = {'entered': False, 'exited': False, 'exception': False}
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with lk.WriteTransaction(lock, enter_fn, exit_fn):
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pass
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assert vals['entered']
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assert vals['exited']
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assert vals['entered_fn']
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assert vals['exited_fn']
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assert vals['acquired_%s' % type]
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assert vals['released_%s' % type]
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assert not vals['exception']
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def test_transaction_with_exception(lock_path):
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@pytest.mark.parametrize(
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"transaction,type",
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[(lk.ReadTransaction, "read"), (lk.WriteTransaction, "write")]
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)
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def test_transaction_with_exception(lock_path, transaction, type):
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class MockLock(AssertLock):
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def assert_acquire_read(self):
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assert not vals['entered_fn']
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assert not vals['exited_fn']
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def assert_release_read(self):
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assert vals['entered_fn']
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assert not vals['exited_fn']
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def assert_acquire_write(self):
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assert not vals['entered_fn']
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assert not vals['exited_fn']
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def assert_release_write(self):
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assert vals['entered_fn']
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assert not vals['exited_fn']
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def enter_fn():
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vals['entered'] = True
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assert vals['acquired_%s' % type]
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vals['entered_fn'] = True
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def exit_fn(t, v, tb):
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vals['exited'] = True
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assert not vals['released_%s' % type]
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vals['exited_fn'] = True
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vals['exception'] = (t or v or tb)
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return exit_result
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lock = lk.Lock(lock_path)
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exit_result = False
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vals = collections.defaultdict(lambda: False)
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lock = MockLock(lock_path, vals)
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def do_read_with_exception():
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with lk.ReadTransaction(lock, enter_fn, exit_fn):
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raise Exception()
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def do_write_with_exception():
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with lk.WriteTransaction(lock, enter_fn, exit_fn):
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raise Exception()
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vals = {'entered': False, 'exited': False, 'exception': False}
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with pytest.raises(Exception):
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do_read_with_exception()
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assert vals['entered']
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assert vals['exited']
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with transaction(lock, acquire=enter_fn, release=exit_fn):
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raise Exception()
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assert vals['entered_fn']
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assert vals['exited_fn']
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assert vals['exception']
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vals = {'entered': False, 'exited': False, 'exception': False}
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with pytest.raises(Exception):
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do_write_with_exception()
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assert vals['entered']
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assert vals['exited']
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# test suppression of exceptions from exit_fn
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exit_result = True
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vals.clear()
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# should not raise now.
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with transaction(lock, acquire=enter_fn, release=exit_fn):
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raise Exception()
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assert vals['entered_fn']
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assert vals['exited_fn']
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assert vals['exception']
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def test_transaction_with_context_manager(lock_path):
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class TestContextManager(object):
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@pytest.mark.parametrize(
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"transaction,type",
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[(lk.ReadTransaction, "read"), (lk.WriteTransaction, "write")]
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)
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def test_transaction_with_context_manager(lock_path, transaction, type):
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class MockLock(AssertLock):
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def assert_acquire_read(self):
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assert not vals['entered_ctx']
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assert not vals['exited_ctx']
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def __enter__(self):
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vals['entered'] = True
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def assert_release_read(self):
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assert vals['entered_ctx']
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assert vals['exited_ctx']
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def __exit__(self, t, v, tb):
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vals['exited'] = True
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vals['exception'] = (t or v or tb)
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def assert_acquire_write(self):
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assert not vals['entered_ctx']
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assert not vals['exited_ctx']
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def exit_fn(t, v, tb):
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vals['exited_fn'] = True
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vals['exception_fn'] = (t or v or tb)
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def assert_release_write(self):
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assert vals['entered_ctx']
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assert vals['exited_ctx']
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lock = lk.Lock(lock_path)
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vals = {'entered': False, 'exited': False, 'exited_fn': False,
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'exception': False, 'exception_fn': False}
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with lk.ReadTransaction(lock, TestContextManager, exit_fn):
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pass
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assert vals['entered']
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assert vals['exited']
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assert not vals['exception']
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assert vals['exited_fn']
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assert not vals['exception_fn']
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vals = {'entered': False, 'exited': False, 'exited_fn': False,
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'exception': False, 'exception_fn': False}
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with lk.ReadTransaction(lock, TestContextManager):
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pass
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assert vals['entered']
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assert vals['exited']
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assert not vals['exception']
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assert not vals['exited_fn']
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assert not vals['exception_fn']
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vals = {'entered': False, 'exited': False, 'exited_fn': False,
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'exception': False, 'exception_fn': False}
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with lk.WriteTransaction(lock, TestContextManager, exit_fn):
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pass
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assert vals['entered']
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assert vals['exited']
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assert not vals['exception']
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assert vals['exited_fn']
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assert not vals['exception_fn']
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vals = {'entered': False, 'exited': False, 'exited_fn': False,
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'exception': False, 'exception_fn': False}
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with lk.WriteTransaction(lock, TestContextManager):
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pass
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assert vals['entered']
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assert vals['exited']
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assert not vals['exception']
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assert not vals['exited_fn']
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assert not vals['exception_fn']
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def test_transaction_with_context_manager_and_exception(lock_path):
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class TestContextManager(object):
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def __enter__(self):
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vals['entered'] = True
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vals['entered_ctx'] = True
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def __exit__(self, t, v, tb):
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vals['exited'] = True
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vals['exception'] = (t or v or tb)
|
||||
assert not vals['released_%s' % type]
|
||||
vals['exited_ctx'] = True
|
||||
vals['exception_ctx'] = (t or v or tb)
|
||||
return exit_ctx_result
|
||||
|
||||
def exit_fn(t, v, tb):
|
||||
assert not vals['released_%s' % type]
|
||||
vals['exited_fn'] = True
|
||||
vals['exception_fn'] = (t or v or tb)
|
||||
return exit_fn_result
|
||||
|
||||
lock = lk.Lock(lock_path)
|
||||
exit_fn_result, exit_ctx_result = False, False
|
||||
vals = collections.defaultdict(lambda: False)
|
||||
lock = MockLock(lock_path, vals)
|
||||
|
||||
def do_read_with_exception(exit_fn):
|
||||
with lk.ReadTransaction(lock, TestContextManager, exit_fn):
|
||||
raise Exception()
|
||||
with transaction(lock, acquire=TestContextManager, release=exit_fn):
|
||||
pass
|
||||
|
||||
def do_write_with_exception(exit_fn):
|
||||
with lk.WriteTransaction(lock, TestContextManager, exit_fn):
|
||||
raise Exception()
|
||||
|
||||
vals = {'entered': False, 'exited': False, 'exited_fn': False,
|
||||
'exception': False, 'exception_fn': False}
|
||||
with pytest.raises(Exception):
|
||||
do_read_with_exception(exit_fn)
|
||||
assert vals['entered']
|
||||
assert vals['exited']
|
||||
assert vals['exception']
|
||||
assert vals['entered_ctx']
|
||||
assert vals['exited_ctx']
|
||||
assert vals['exited_fn']
|
||||
assert vals['exception_fn']
|
||||
|
||||
vals = {'entered': False, 'exited': False, 'exited_fn': False,
|
||||
'exception': False, 'exception_fn': False}
|
||||
with pytest.raises(Exception):
|
||||
do_read_with_exception(None)
|
||||
assert vals['entered']
|
||||
assert vals['exited']
|
||||
assert vals['exception']
|
||||
assert not vals['exited_fn']
|
||||
assert not vals['exception_ctx']
|
||||
assert not vals['exception_fn']
|
||||
|
||||
vals = {'entered': False, 'exited': False, 'exited_fn': False,
|
||||
'exception': False, 'exception_fn': False}
|
||||
with pytest.raises(Exception):
|
||||
do_write_with_exception(exit_fn)
|
||||
assert vals['entered']
|
||||
assert vals['exited']
|
||||
assert vals['exception']
|
||||
assert vals['exited_fn']
|
||||
assert vals['exception_fn']
|
||||
vals.clear()
|
||||
with transaction(lock, acquire=TestContextManager):
|
||||
pass
|
||||
|
||||
vals = {'entered': False, 'exited': False, 'exited_fn': False,
|
||||
'exception': False, 'exception_fn': False}
|
||||
with pytest.raises(Exception):
|
||||
do_write_with_exception(None)
|
||||
assert vals['entered']
|
||||
assert vals['exited']
|
||||
assert vals['exception']
|
||||
assert vals['entered_ctx']
|
||||
assert vals['exited_ctx']
|
||||
assert not vals['exited_fn']
|
||||
assert not vals['exception_ctx']
|
||||
assert not vals['exception_fn']
|
||||
|
||||
# below are tests for exceptions with and without suppression
|
||||
def assert_ctx_and_fn_exception(raises=True):
|
||||
vals.clear()
|
||||
|
||||
if raises:
|
||||
with pytest.raises(Exception):
|
||||
with transaction(
|
||||
lock, acquire=TestContextManager, release=exit_fn):
|
||||
raise Exception()
|
||||
else:
|
||||
with transaction(
|
||||
lock, acquire=TestContextManager, release=exit_fn):
|
||||
raise Exception()
|
||||
|
||||
assert vals['entered_ctx']
|
||||
assert vals['exited_ctx']
|
||||
assert vals['exited_fn']
|
||||
assert vals['exception_ctx']
|
||||
assert vals['exception_fn']
|
||||
|
||||
def assert_only_ctx_exception(raises=True):
|
||||
vals.clear()
|
||||
|
||||
if raises:
|
||||
with pytest.raises(Exception):
|
||||
with transaction(lock, acquire=TestContextManager):
|
||||
raise Exception()
|
||||
else:
|
||||
with transaction(lock, acquire=TestContextManager):
|
||||
raise Exception()
|
||||
|
||||
assert vals['entered_ctx']
|
||||
assert vals['exited_ctx']
|
||||
assert not vals['exited_fn']
|
||||
assert vals['exception_ctx']
|
||||
assert not vals['exception_fn']
|
||||
|
||||
# no suppression
|
||||
assert_ctx_and_fn_exception(raises=True)
|
||||
assert_only_ctx_exception(raises=True)
|
||||
|
||||
# suppress exception only in function
|
||||
exit_fn_result, exit_ctx_result = True, False
|
||||
assert_ctx_and_fn_exception(raises=False)
|
||||
assert_only_ctx_exception(raises=True)
|
||||
|
||||
# suppress exception only in context
|
||||
exit_fn_result, exit_ctx_result = False, True
|
||||
assert_ctx_and_fn_exception(raises=False)
|
||||
assert_only_ctx_exception(raises=False)
|
||||
|
||||
# suppress exception in function and context
|
||||
exit_fn_result, exit_ctx_result = True, True
|
||||
assert_ctx_and_fn_exception(raises=False)
|
||||
assert_only_ctx_exception(raises=False)
|
||||
|
||||
|
||||
def test_lock_debug_output(lock_path):
|
||||
host = socket.getfqdn()
|
||||
|
|
|
|||
|
|
@ -107,7 +107,8 @@ def read_transaction(self, key):
|
|||
|
||||
"""
|
||||
return ReadTransaction(
|
||||
self._get_lock(key), lambda: open(self.cache_path(key)))
|
||||
self._get_lock(key), acquire=lambda: open(self.cache_path(key))
|
||||
)
|
||||
|
||||
def write_transaction(self, key):
|
||||
"""Get a write transaction on a file cache item.
|
||||
|
|
@ -117,6 +118,10 @@ def write_transaction(self, key):
|
|||
moves the file into place on top of the old file atomically.
|
||||
|
||||
"""
|
||||
# TODO: this nested context manager adds a lot of complexity and
|
||||
# TODO: is pretty hard to reason about in llnl.util.lock. At some
|
||||
# TODO: point we should just replace it with functions and simplify
|
||||
# TODO: the locking code.
|
||||
class WriteContextManager(object):
|
||||
|
||||
def __enter__(cm): # noqa
|
||||
|
|
@ -142,7 +147,8 @@ def __exit__(cm, type, value, traceback): # noqa
|
|||
else:
|
||||
os.rename(cm.tmp_filename, cm.orig_filename)
|
||||
|
||||
return WriteTransaction(self._get_lock(key), WriteContextManager)
|
||||
return WriteTransaction(
|
||||
self._get_lock(key), acquire=WriteContextManager)
|
||||
|
||||
def mtime(self, key):
|
||||
"""Return modification time of cache file, or 0 if it does not exist.
|
||||
|
|
|
|||
Loading…
Reference in a new issue