============
Transactions

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:alt: Python versions

This package contains a generic transaction implementation for Python. It is
mainly used by the ZODB.

See http://transaction.readthedocs.org/en/latest for narrative documentation
on its usage.

=========
Changes

5.0 (2024-09-18)

Add final support for Python 3.13.
Drop support for Python 3.7.

4.0 (2023-11-13)

Drop support for Python 2.7, 3.5, 3.6.
Drop support for deprecated python setup.py test..
Add support for Python 3.12.
Add preliminary support for Python 3.13a2.

3.1.0 (2023-03-17)

Add support for Python 3.9, 3.10, 3.11.

3.0.1 (2020-12-11)

Exception raised by a before commit hook is no longer hidden. No
further commit hooks are called and exception is propagated to
the caller of commit(). See
#95 <https://github.com/zopefoundation/transaction/pull/95>_.

3.0.0 (2019-12-11)

Drop support for Python 3.4.
Add support for Python 3.8.
Drop support for legacy transaction APIs including
Transaction.register() and old ZODB3-style datamanagers. See
issue 89 <https://github.com/zopefoundation/transaction/issues/89>_.
TransactionManager.run now commits/aborts the transaction
"active" after the execution of func (and no longer the initial
transaction which might already have been committed/aborted by func)
(#58 <https://github.com/zopefoundation/transaction/issues/58>_).

It aborts the transaction now for all exceptions raised by func - even
if it is only an instance of BaseException but not of Exception,
such as e.g. a SystemExit or KeyboardInterupt exception.
Support abort hooks (symmetrically to commit hooks)
(#77 <https://github.com/zopefoundation/transaction/issues/77>_).
Make Transaction drop references to its hooks, manager,
synchronizers and data after a successful commit() and after
any abort(). This helps avoid potential cyclic references. See
issue 82 <https://github.com/zopefoundation/transaction/issues/82>_.
Allow synchronizers to access Transaction.data() when their
afterCompletion method is called while aborting a transaction.
Make it safe to call Transaction.abort() more than once. The
second and subsequent calls are no-ops. Previously a
ValueError(Foreign transaction) would be raised.

2.4.0 (2018-10-23)

Changed the implementation of ThreadTransactionManager to be a
thread.local that wraps a TransactionManager rather than a
thread.local that inherits from TransactionManager. It now exposes a
manager attribute that allows access to the wrapped transaction
manager to allow cross thread calls. See issue 68 <https://github.com/zopefoundation/transaction/pull/68>_.

2.3.0 (2018-10-19)

Add support for Python 3.7.
Reach 100% test coverage.
Fix transaction.manager.run formatting transaction notes when
given a mix of byte and text strings, such as can happen in Python 2
with unicode_literals.

2.2.1 (2018-03-27)

Make documentation index more user friendly; move old docs to developer
section.
Don't crash when printing tracebacks in IPython on Python 2.
(This addresses https://github.com/zopefoundation/transaction/issues/5.)

2.2.0 (2018-02-27)

Add support for Python 3.6.
Drop support for Python 3.3.
Add isRetryableError to the
transaction.interfaces.ITransaction interface to allow external
systems to query whether an exception is retryable (transient) by
any of the attached data managers. Any
transaction.interfaces.TransientError is considered retryable
but a data manager may also consider other exceptions on a
per-instance basis.

See https://github.com/zopefoundation/transaction/pull/38

2.1.2 (2017-03-11)

To avoid leaking memory, don't include unexpected value in warnings
about non-text transaction meta data.

2.1.1 (2017-03-11)

For backward compatibility, relax the requirements that transaction
meta data (user or description) be text:
- If None is assigned, the assignment is ignored.
- If a non-text value is assigned, a warning is issued and the value
  is converted to text. If the value is a binary string, it will be
  decoded with the UTF-8 encoding the replace error policy.

2.1.0 (2017-02-08)

Added a transaction-manager explicit mode. Explicit mode makes some
kinds of application bugs easier to detect and potentially allows data
managers to manage resources more efficiently.

(This addresses https://github.com/zopefoundation/transaction/issues/35.)

2.0.3 (2016-11-17)

The user and description fields must now be set with text (unicode)
data. Previously, if bytes were provided, they'd be decoded as
ASCII. It was decided that this would lead to bugs that were hard
to test for.

Also, the transaction meta-data field, extended_info has been
renamed to extension.

2.0.2 (2016-11-13)

Fixed: Some legacy applications expect the transaction _extension
attribute to be mutable and it wasn't.

2.0.1 (2016-11-11)

The transaction user and description attributes are now
defined to be text (unicode) as opposed to Python the str type.
Added the extended_info transaction attribute which contains
transaction meta data. (The _extension attribute is retained as
an alias for backward compatibility.)

The transaction interface, ITransaction, now requires
extended_info keys to be text (unicode) and values to be
JSON-serializable.
Removed setUser from ITransaction. We'll keep the method
indefinitely, but it's unseemly in ITransaction. :)

The main purpose of these changes is to tighten up the text
specification of user, description and extended_info keys, and to give
us more flexibility in the future for serializing extended info. It's
possible that these changes will be breaking, so we're also increasing
the major version number.

1.7.0 (2016-11-08)

Added a transaction-manager run method for running a function as a
transaction, retrying as necessary on transient errors.
Fixed the transaction manager attempts method. It didn't stop
repeating when there wasn't an error.
Corrected ITransaction by removing beforeCommitHook (which is no longer
implemented) and removing 'self' from two methods.

1.6.1 (2016-06-10)

Fixed: Synchonizers that registered with transaction managers when
transactions were in progress didn't have their newTransaction
methods called to let them know of the in-progress transactions.

1.6.0 (2016-05-21)

New transaction API for storing data on behalf of objects, such as
data managers.
Drop references to data managers joined to a transaction when it is
committed or aborted.

1.5.0 (2016-05-05)

Drop support for Python 2.6 and 3.2.
Add support for Python 3.5.
Added APIs for interogating and clearing internal state to support
client tests.

1.4.4 (2015-05-19)

Use the standard valuerefs() method rather than relying on
implementation details of WeakValueDictionary in WeakSet.
Add support for PyPy3.
Require 100% branch coverage (in addition to 100% statement coverage).

1.4.3 (2014-03-20)

Add support for Python 3.4.

1.4.2 (skipped)

Released in error as 1.4.3.

1.4.1 (2013-02-20)

Document that values returned by sortKey must be strings, in order
to guarantee total ordering.
Fix occasional RuntimeError: dictionary changed size during iteration errors
in transaction.weakset on Python 3.

1.4.0 (2013-01-03)

Updated Trove classifiers.

1.4.0b1 (2012-12-18)

Converted existing doctests into Sphinx documentation (snippets are
exercised via 'tox').
100% unit test coverage.
Backward incompatibility: raise ValueError rather than AssertionError
for runtime errors:
- In Transaction.doom if the transaction is in a non-doomable state.
- In TransactionManager.attempts if passed a non-positive value.
- In TransactionManager.free if passed a foreign transaction.
Declared support for Python 3.3 in setup.py, and added tox testing.
When a non-retryable exception was raised as the result of a call to
transaction.manager.commit within the "attempts" machinery, the
exception was not reraised properly. Symptom: an unrecoverable exception
such as Unsupported: Storing blobs in <somestorage> is not supported.
would be swallowed inappropriately.

1.3.0 (2012-05-16)

Added Sphinx API docuementation.
Added explicit support for PyPy.
Dropped use of Python3-impatible zope.interface.implements class
advisor in favor of zope.interface.implementer class decorator.
Added support for continuous integration using tox and jenkins.
Added setup.py docs alias (installs Sphinx and dependencies).
Added setup.py dev alias (runs setup.py develop plus installs
nose and coverage).
Python 3.3 compatibility.
Fix "for attempt in transaction.attempts(x)" machinery, which would not
retry a transaction if its implicit call to .commit() itself raised a
transient error. Symptom: seeing conflict errors even though you thought
you were retrying some number of times via the "attempts" machinery (the
first attempt to generate an exception during commit would cause that
exception to be raised).

1.2.0 (2011-12-05)

New Features:

Python 3.2 compatibility.
Dropped Python 2.4 and 2.5 compatibility (use 1.1.1 if you need to use
"transaction" under these Python versions).

1.1.1 (2010-09-16)

Bug Fixes:

Code in _transaction.py held on to local references to traceback
objects after calling sys.exc_info() to get one, causing
potential reference leakages.
Fixed hexlify NameError in transaction._transaction.oid_repr
and add test.

1.1.0 (1010-05-12)

New Features:

Transaction managers and the transaction module can be used with the
with statement to define transaction boundaries, as in::

with transaction:
... do some things ...
See transaction/tests/convenience.txt for more details.
There is a new iterator function that automates dealing with
transient errors (such as ZODB confict errors). For example, in::

for attempt in transaction.attempts(5):
with attempt:
... do some things ..
If the work being done raises transient errors, the transaction will
be retried up to 5 times.

See transaction/tests/convenience.txt for more details.

Bugs fixed:

Fixed a bug that caused extra commit calls to be made on data
managers under certain special circumstances.

https://mail.zope.org/pipermail/zodb-dev/2010-May/013329.html
When threads were reused, transaction data could leak accross them,
causing subtle application bugs.

https://bugs.launchpad.net/zodb/+bug/239086

1.0.1 (2010-05-07)

LP #142464: remove double newline between log entries: it makes doing
smarter formatting harder.
Updated tests to remove use of deprecated zope.testing.doctest.

1.0.0 (2009-07-24)

Fix test that incorrectly relied on the order of a list that was generated
from a dict.
Remove crufty DEPENDENCIES.cfg left over from zpkg.

1.0a1 (2007-12-18)

Initial release, branched from ZODB trunk on 2007-11-08 (aka
"3.9.0dev").
Remove (deprecated) support for beforeCommitHook alias to
addBeforeCommitHook.
Add weakset tests.
Remove unit tests that depend on ZODB.tests.utils from
test_transaction (these are actually integration tests).

Dependency	Optional
zope.interface	false
coverage	true
repoze.sphinx.autointerface	true
Sphinx	true

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