Nti.transactions

==================

- Require at least version 3.0 of the ``transaction`` package.

- Drop dependency on the ``dm.transaction.aborthook`` package. That
functionality is now natively provided in transaction 3.0.

==================

- Fix logging of long duration commits. See `issue 44
<https://github.com/NextThought/nti.transactions/issues/44>`_.

- Add logging and a metric
(``transaction.side_effect_free_violation``) for transactions that
claim to have no side effects, but which actually result in joined
resource managers. This can indicate unnecessarily throwing away
work. See `issue 45 <https://github.com/NextThought/nti.transactions/issues/45>`_.

==================

- Add support for Python 3.8.

- Refactor internal implementation details. Instead of importing
everything from ``nti.transactions.transactions``, more specific
modules are used to group objects by function. The old imports
continue to work. In 4.0 they will generate a deprecation warning
and in 5.0 they will be removed.

- Add a Pyramid tween to manage transactions and transaction retries.
Various settings can be configured as Pyramid deployment settings
(e.g., in the ini file).

- Make the transaction loop increase the time it sleeps between
retries following the `random binary exponential backoff algorithm
<https://en.wikipedia.org/wiki/Exponential_backoff>`_ used by Ethernet.

- Reduce the default number of attempts to 4 (one attempt and 3
retries). See `issue 35 <https://github.com/NextThought/nti.transactions/issues/35>`_.

- Make the transaction loop emit more metrics. See `issue 31
<https://github.com/NextThought/nti.transactions/issues/31>`_.

- Make commit logging now always happen at least at the debug level,
escalating to warning for long commits. It also includes the number
of retries taken and the amount of time spent sleeping. See `issue
32 <https://github.com/NextThought/nti.transactions/issues/32>`_.

- Make the transaction loop emit events (using ``zope.event``) at certain parts of the
transaction lifecycle. See `issue 33 <https://github.com/NextThought/nti.transactions/issues/33>`_.

==================

- Make ``TransactionLoop`` place its transaction manager in explicit
mode. This can be faster and is easier to reason about, but forbids
the called handler from manually calling ``begin()``, ``abort()`` or
``commit()``. See `issue 20
<https://github.com/NextThought/nti.transactions/issues/20>`_.

- Move ``transaction.begin()`` out of the block of code that is
retried. Previously, an error there would probably be raised
*anyway* and not retried, unless a subclass had made customizations.

- Add ``setUp`` and ``tearDown`` methods to TransactionLoop to give
subclasses a place to hook into the inners of the transaction loop.
This is particularly helpful if they need to do something after the
transaction manager has been put in explicit mode. See `issue 22
<https://github.com/NextThought/nti.transactions/issues/22>`_.

==================

- Fix compatibility with perfmetrics 3.0: drop ``from __future__
import unicode_literals``.

==================

- Use the new public ``isRetryableError`` in transaction 2.2. The
interface for this package is unchanged, but a major version bump of
a dependency necessitates a major bump here. See `issue 12
<https://github.com/NextThought/nti.transactions/issues/12>`_.

- Test support for Python 3.7; remove test support for Python 3.4.

- ``TransactionLoop`` is more careful to not keep traceback objects
around, especially on Python 2.