root / snf-common / synnefo / lib / db / pooled_psycopg2 / __init__.py @ 5f6ad491
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# Copyright 2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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#
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import psycopg2 |
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from synnefo.lib.pool import ObjectPool |
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from select import select |
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import logging |
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log = logging.getLogger(__name__) |
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_pool_kwargs = None
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_pool = None
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# How many times to retry on getting a live connection
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# from the pool, before giving up.
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RETRY_LIMIT = 1000
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class PooledConnection(object): |
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"""Thin wrapper around a psycopg2 connection for a pooled connection.
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It takes care to put itself back into the pool upon connection closure.
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"""
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def __init__(self, pool, conn): |
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log.debug("INIT-POOLED: pool = %s, conn = %s", pool, conn)
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self._pool = pool
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self._conn = conn
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def close(self): |
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log.debug("CLOSE-POOLED: self._pool = %s", self._pool) |
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if not self._pool: |
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return
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pool = self._pool
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log.debug("PUT-POOLED-BEFORE: about to return %s to the pool", self) |
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pool.pool_put(self)
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log.debug("PUT-POOLED-AFTER: returned %s to the pool", self) |
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def __getattr__(self, attr): |
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"""Proxy every other call to the real connection"""
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return getattr(self._conn, attr) |
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def __setattr__(self, attr, val): |
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if attr not in ("_pool", "_conn"): |
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setattr(self._conn, attr, val) |
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object.__setattr__(self, attr, val) |
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class Psycopg2ConnectionPool(ObjectPool): |
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"""A synnefo.lib.pool.ObjectPool of psycopg2 connections.
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Every connection knows how to return itself to the pool
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when it gets close()d.
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"""
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def __init__(self, **kw): |
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ObjectPool.__init__(self, size=kw["synnefo_poolsize"]) |
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kw.pop("synnefo_poolsize")
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self._connection_args = kw
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def _pool_create(self): |
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log.info("CREATE: about to get a new connection from psycopg2")
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conn = psycopg2._original_connect(**self._connection_args)
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log.info("CREATED: got connection %s from psycopg2", conn)
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return PooledConnection(self, conn) |
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def _pool_verify_execute(pooledconn): |
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try:
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cursor = pooledconn.cursor() |
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cursor.execute("SELECT 1")
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except psycopg2.Error:
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# The connection has died.
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pooledconn.close() |
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return False |
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return True |
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def _pool_verify(self, conn): |
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if select((conn.fileno(),), (), (), 0)[0]: |
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return False |
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return True |
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def _pool_cleanup(self, pooledconn): |
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log.debug("CLEANING, conn = %d", id(pooledconn)) |
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try:
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# Reset this connection before putting it back
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# into the pool
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pooledconn.rollback() |
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except psycopg2.Error:
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# Since we're not going to be putting the psycopg2 connection
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# back into the pool, close it uncoditionally.
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log.error("Detected dead connection, conn = %d, %s",
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id(pooledconn), pooledconn)
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try:
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pooledconn._conn.close() |
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except:
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pass
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return True |
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return False |
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def _init_pool(kw): |
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global _pool
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global _pool_kwargs
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_pool_kwargs = kw |
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_pool = Psycopg2ConnectionPool(**kw) |
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def _get_pool(kw): |
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if not _pool: |
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log.debug("INIT-POOL: Initializing DB connection pool")
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_init_pool(kw) |
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if _pool_kwargs != kw:
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raise NotImplementedError(("Requested pooled psycopg2 connection with " |
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"args %s != %s." % (kw, _pool_kwargs)))
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return _pool
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def _pooled_connect(**kw): |
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poolsize = kw.get("synnefo_poolsize", 0) |
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if not poolsize: |
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kw.pop("synnefo_poolsize", None) |
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return psycopg2._original_connect(**kw)
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pool = _get_pool(kw) |
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log.debug("GET-POOL: Pool: %r", pool)
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r = pool.pool_get() |
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log.debug("GOT-POOL: Got connection %d from pool %r", id(r), pool) |
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return r
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def monkey_patch_psycopg2(): |
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"""Monkey-patch psycopg2's connect(), to retrieve connections from a pool.
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To enable pooling, you need to pass a synnefo_poolsize argument
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inside psycopg2's connection options.
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"""
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if hasattr(psycopg2, '_original_connect'): |
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return
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psycopg2._original_connect = psycopg2.connect |
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psycopg2.connect = _pooled_connect |