--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pgmanager.py Fri Aug 12 14:39:49 2011 +0200
@@ -0,0 +1,340 @@
+# -*- coding: utf-8 -*-
+#
+# PgManager - manage database connections
+#
+# Requires: Python 2.6, psycopg2
+#
+# Copyright (c) 2010, 2011 Radek Brich <radek.brich@devl.cz>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+"""Postgres database connection manager
+
+PgManager wraps psycopg2 connect function, adding following features:
+
+ * Manage database connection parameters - link connection parameters
+ to an unique identifier, retrieve connection object by this identifier
+
+ * Connection pooling - connections with same identifier are pooled and reused
+
+ * Easy query using the with statement - retrieve cursor directly by connection
+ identifier, don't worry about connections
+
+ * Dict rows - cursor has additional methods like fetchall_dict(), which
+ returns dict row instead of ordinary list-like row
+
+Example:
+
+import pgmanager
+
+pgm = pgmanager.get_instance()
+pgm.create_conn(hostaddr='127.0.0.1', dbname='postgres')
+
+with pgm.cursor() as curs:
+ curs.execute('SELECT now() AS now')
+ row = curs.fetchone_dict()
+ print row.now
+
+First, we have obtained PgManager instance. This is like calling
+PgManager(), although in our example the instance is global. That means
+getting the instance in another module brings us all the defined connections
+etc.
+
+On second line we created connection named 'default' (this name can be left out).
+The with statement obtains connection (actually connects to database when needed),
+then returns cursor for this connection. On exit, the connection is returned
+to the pool or closed (depending on number of connections on pool and setting
+of keep_open parameter).
+
+The row returned by fetchone_dict() is special dict object, which can be accessed
+using item or attribute access, that is row['now'] or row.now.
+"""
+
+from contextlib import contextmanager
+import logging
+import threading
+import select
+
+import psycopg2
+import psycopg2.extensions
+
+from psycopg2 import DatabaseError, IntegrityError
+
+
+class PgManagerError(Exception):
+
+ pass
+
+
+class ConnectionInfo:
+
+ def __init__(self, dsn, isolation_level=None, init_statement=None, keep_open=1):
+ self.dsn = dsn
+ self.isolation_level = isolation_level
+ self.init_statement = init_statement
+ self.keep_open = keep_open
+
+
+class RowDict(dict):
+
+ def __getattr__(self, key):
+ return self[key]
+
+
+class Cursor(psycopg2.extensions.cursor):
+
+ def execute(self, query, args=None):
+ try:
+ return super(Cursor, self).execute(query, args)
+ finally:
+ log.debug(self.query.decode('utf8'))
+
+ def callproc(self, procname, args=None):
+ try:
+ return super(Cursor, self).callproc(procname, args)
+ finally:
+ log.debug(self.query.decode('utf8'))
+
+ def row_dict(self, row, lstrip=None):
+ adjustname = lambda a: a
+ if lstrip:
+ adjustname = lambda a: a.lstrip(lstrip)
+ return RowDict(zip([adjustname(desc[0]) for desc in self.description], row))
+
+ def fetchone_dict(self, lstrip=None):
+ row = super(Cursor, self).fetchone()
+ if row is None:
+ return None
+ return self.row_dict(row, lstrip)
+
+ def fetchall_dict(self, lstrip=None):
+ rows = super(Cursor, self).fetchall()
+ return [self.row_dict(row, lstrip) for row in rows]
+
+ def fetchone_adapted(self):
+ '''Like fetchone() but values are quoted for direct inclusion in SQL query.
+
+ This is useful when you need to generate SQL script from data returned
+ by the query. Use mogrify() for simple cases.
+
+ '''
+ row = super(Cursor, self).fetchone()
+ if row is None:
+ return None
+ return [self.mogrify('%s', [x]).decode('utf8') for x in row]
+
+ def fetchall_adapted(self):
+ '''Like fetchall() but values are quoted for direct inclusion in SQL query.'''
+ rows = super(Cursor, self).fetchall()
+ return [[self.mogrify('%s', [x]).decode('utf8') for x in row] for row in rows]
+
+
+class Connection(psycopg2.extensions.connection):
+
+ def cursor(self, name=None):
+ if name is None:
+ return super(Connection, self).cursor(cursor_factory=Cursor)
+ else:
+ return super(Connection, self).cursor(name, cursor_factory=Cursor)
+
+
+class PgManager:
+
+ def __init__(self):
+ self.conn_known = {} # available connections
+ self.conn_pool = {}
+ self.lock = threading.Lock()
+
+ def __del__(self):
+ for conn in tuple(self.conn_known.keys()):
+ self.destroy_conn(conn)
+
+ def create_conn(self, name='default', isolation_level=None, dsn=None, **kw):
+ '''Create named connection.'''
+ if name in self.conn_known:
+ raise PgManagerError('Connection name "%s" already registered.' % name)
+
+ if dsn is None:
+ dsn = ' '.join([x[0]+'='+str(x[1]) for x in kw.items()])
+
+ isolation_level = self._normalize_isolation_level(isolation_level)
+ ci = ConnectionInfo(dsn, isolation_level)
+
+ self.conn_known[name] = ci
+ self.conn_pool[name] = []
+
+ def close_conn(self, name='default'):
+ '''Close all connections of given name.
+
+ Connection credentials are still saved.
+
+ '''
+ while len(self.conn_pool[name]):
+ conn = self.conn_pool[name].pop()
+ conn.close()
+
+ def destroy_conn(self, name='default'):
+ '''Destroy connection.
+
+ Counterpart of create_conn.
+
+ '''
+ if not name in self.conn_known:
+ raise PgManagerError('Connection name "%s" not registered.' % name)
+
+ self.close_conn(name)
+
+ del self.conn_known[name]
+ del self.conn_pool[name]
+
+ def get_conn(self, name='default'):
+ '''Get connection of name 'name' from pool.'''
+ self.lock.acquire()
+ try:
+ if not name in self.conn_known:
+ raise PgManagerError("Connection name '%s' not registered." % name)
+
+ conn = None
+ while len(self.conn_pool[name]) and conn is None:
+ conn = self.conn_pool[name].pop()
+ if conn.closed:
+ conn = None
+
+ if conn is None:
+ ci = self.conn_known[name]
+ conn = psycopg2.connect(ci.dsn, connection_factory=Connection)
+ if not ci.isolation_level is None:
+ conn.set_isolation_level(ci.isolation_level)
+ if ci.init_statement:
+ curs = conn.cursor()
+ curs.execute(ci.init_statement)
+ curs.close()
+ finally:
+ self.lock.release()
+ return conn
+
+ def put_conn(self, conn, name='default'):
+ '''Put connection back to pool.
+
+ Name must be same as used for get_conn,
+ otherwise things become broken.
+
+ '''
+ self.lock.acquire()
+ try:
+ if not name in self.conn_known:
+ raise PgManagerError("Connection name '%s' not registered." % name)
+
+ if len(self.conn_pool[name]) >= self.conn_known[name].keep_open:
+ conn.close()
+ return
+
+ if conn.get_transaction_status() == psycopg2.extensions.TRANSACTION_STATUS_UNKNOWN:
+ conn.close()
+ return
+
+ # connection returned to the pool must not be in transaction
+ if conn.get_transaction_status() != psycopg2.extensions.TRANSACTION_STATUS_IDLE:
+ conn.rollback()
+
+ self.conn_pool[name].append(conn)
+ finally:
+ self.lock.release()
+
+ @contextmanager
+ def cursor(self, name='default'):
+ '''Cursor context.
+
+ Uses any connection of name 'name' from pool
+ and returns cursor for that connection.
+
+ '''
+ conn = self.get_conn(name)
+
+ try:
+ curs = conn.cursor()
+ yield curs
+ finally:
+ curs.close()
+ self.put_conn(conn, name)
+
+ def wait_for_notify(self, name='default', timeout=5):
+ '''Wait for asynchronous notifies, return the last one.
+
+ Returns None on timeout.
+
+ '''
+ conn = self.get_conn(name)
+
+ try:
+ # any residual notify?
+ # then return it, that should not break anything
+ if conn.notifies:
+ return conn.notifies.pop()
+
+ if select.select([conn], [], [], timeout) == ([], [], []):
+ # timeout
+ return None
+ else:
+ conn.poll()
+
+ # return just the last notify (we do not care for older ones)
+ if conn.notifies:
+ return conn.notifies.pop()
+ return None
+ finally:
+ # clean notifies
+ while conn.notifies:
+ conn.notifies.pop()
+ self.put_conn(conn, name)
+
+ def _normalize_isolation_level(self, level):
+ if type(level) == str:
+ if level.lower() == 'autocommit':
+ return psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT
+ if level.lower() == 'read_committed':
+ return psycopg2.extensions.ISOLATION_LEVEL_READ_COMMITTED
+ if level.lower() == 'serializable':
+ return psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE
+ raise PgManagerError('Unknown isolation level name: "%s"', level)
+ return level
+
+
+try:
+ NullHandler = logging.NullHandler
+except AttributeError:
+ class NullHandler(logging.Handler):
+ def emit(self, record):
+ pass
+
+
+log = logging.getLogger("pgmanager")
+log.addHandler(NullHandler())
+
+
+instance = None
+
+
+def get_instance():
+ global instance
+ if instance is None:
+ instance = PgManager()
+ return instance
+
+