On Thu, 2002-05-02 at 15:57, Costas Malamas wrote:
> I remember there was a conversation here about DBPool.py and how it is not
> really pooling DB Connections. Has anybody attacked this problem?
>
> Thanks,
>
I've got a ConnectionPool class that I wrote.
And your welcome to have a look at it. It
would be nice if it inherited from Configurable
so that max size would work. Also right now
it only pools connections to one database. That
should be easy to change though.
--Karl
> Costas
>
>
>
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#!/usr/bin/env python
import threading
import Queue
import psycopg
import time
GET_TIMEOUT = 10 # roughly seconds
GET_WAIT_INTERVAL = .005 # roughly seconds
class ConnectionPool:
busy_connections = None
connections = None
lock = threading.Lock()
def __init__(self, MAX_CONNECTIONS=5):
ConnectionPool.lock.acquire()
if ConnectionPool.connections == None:
ConnectionPool.connections = Queue.Queue(MAX_CONNECTIONS)
ConnectionPool.busy_connections = []
for i in range(MAX_CONNECTIONS):
ConnectionPool.connections.put(psycopg.connect('host=localhost dbname=shipeze'))
ConnectionPool.lock.release()
def get(self):
timeout = 0
while timeout < GET_TIMEOUT:
try:
conn = ConnectionPool.connections.get_nowait() # throws QEE
bconns = ConnectionPool.busy_connections
lock = ConnectionPool.lock
try:
lock.acquire()
if conn in bconns:
raise ConnectionPoolInternalError('%s already allocated' % str(conn))
else:
bconns.append(conn)
return conn
finally:
if lock.locked(): lock.release()
except Queue.Empty:
timeout += GET_WAIT_INTERVAL
print 'Waiting for connection for %f seconds' % timeout
time.sleep(GET_WAIT_INTERVAL)
# got here so we timed out on the connection
raise ConnectionPoolTimeout()
def put(self, conn):
lock = ConnectionPool.lock
bconns = ConnectionPool.busy_connections
try:
lock.acquire()
while conn in bconns:
bconns.remove(conn)
lock.release()
try:
ConnectionPool.connections.put_nowait(conn) # throws QFE
except Queue.Full:
raise ConnectionPoolInternalError('Too many connection in pool: %s' % str(conn))
finally:
if lock.locked(): lock.release()
class ConnectionPoolTimeout(Exception): pass
class ConnectionPoolInternalError(Exception):
def __init__(self, message='Unknown Internal Error'):
self.message = message
def __str__(self):
return self.message
