8000 Allow choosing a Psycopg implementation, add support for psycopg2cffi. · wulczer/txpostgres@f019075 · GitHub
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Allow choosing a Psycopg implementation, add support for psycopg2cffi.
Centralize code that detects available Psycopg implementations. A particular implementation can now be forced using an environment variable. A new fallback option, psycopg2cffi, has been added. Fixes #30.
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‎NEWS

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What's new in txpostgres 1.3.0
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------------------------------
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- try using psycopg2cffi before falling back to psycopg2-ctypes
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(while still prefering straingh psycopg2)
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- allow choosing the exact psycopg2 implementation using an
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environment variable
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What's new in txpostgres 1.2.0
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------------------------------
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‎doc/usage.rst

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You can run this snippet and then try restarting the database. Logging lines
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should appear, as the connection gets automatically recovered.
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Choosing a Psycopg implementation
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---------------------------------
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To use txpostgres, you will need a recent enough version of Psycopg_, namely
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2.2.0 or later. Since parts of Psycopg are written in C, it is not available
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on some Python implementations, like PyPy. When first imported, txpostgres
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will try to detect if an API-compatible implementation of Psycopg is available.
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You can force a certain implementation to be used by exporing an environment
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variable `TXPOSTGRES_PSYCOPG_IMPL`. Recognized values are:
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psycopg2
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Force using Psycopg_, do not try any fallbacks.
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psycopg2cffi
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Use psycopg2cffi_, a psycopg2 implementation based on cffi, known to work on
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PyPy.
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psycopg2ct
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Use psycopg2ct_, an older psycopg2 implementation using ctypes, also
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compatible with PyPy.
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.. _Psycopg: http://initd.org/psycopg/
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.. _psycopg2cffi: https://github.com/chtd/psycopg2cffi
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.. _psycopg2ct: https://github.com/mvantellingen/psycopg2-ctypes

‎test/test_txpostgres.py

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import os
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from __future__ import absolute_import
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try:
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import psycopg2
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import psycopg2.extensions
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except ImportError:
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# try psycopg2-ctypes
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try:
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import psycopg2ct as psycopg2
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except ImportError:
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raise ImportError('no module named psycopg2 or psycopg2ct')
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import os
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from txpostgres.psycopg2_impl import psycopg2
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from txpostgres import txpostgres, reconnection
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from twisted.trial import unittest

‎txpostgres/psycopg2_impl.py

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"""
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Choose the implementation of psycopg2.
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"""
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import os
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def _try_psycopg2_impl():
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# check for explicit request to use a specific implementation
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_library = os.getenv("TXPOSTGRES_PSYCOPG_IMPL")
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if _library == "psycopg2":
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import psycopg2
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return psycopg2
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if _library == "psycopg2cffi":
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import psycopg2cffi as psycopg2
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return psycopg2
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if _library == "psycopg2ct":
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import psycopg2ct as psycopg2
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return psycopg2
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# try various implementations until one works
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try:
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import psycopg2
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return psycopg2
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except ImportError:
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pass
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try:
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import psycopg2cffi as psycopg2
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return psycopg2
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except ImportError:
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pass
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try:
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import psycopg2ct as psycopg2
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return psycopg2
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except ImportError:
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pass
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raise ImportError('no module named psycopg2, psycopg2cffi or psycopg2ct')
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psycopg2 = _try_psycopg2_impl()
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del _try_psycopg2_impl

‎txpostgres/reconnection.py

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"""
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from __future__ import absolute_import
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import psycopg2
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from twisted.internet import defer
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from twisted.python import log
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from txpostgres import retrying
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from txpostgres.psycopg2_impl import psycopg2
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from txpostgres.txpostgres import RollbackFailed
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‎txpostgres/txpostgres.py

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.. _issue tracker: https://github.com/wulczer/txpostgres/issues
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.. _documentation: http://txpostgres.readthedocs.org/
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"""
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try:
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import psycopg2
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except ImportError:
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# try psycopg2-ctypes
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try:
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import psycopg2ct as psycopg2
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except ImportError:
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raise ImportError('no module named psycopg2 or psycopg2ct')
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from __future__ import absolute_import
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from zope.interface import implements
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from twisted.internet import interfaces, main, defer, task
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from twisted.python import failure, log
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from txpostgres.psycopg2_impl import psycopg2
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try:
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psycopg2.extensions.POLL_OK
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except AttributeError:

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