id very much prefer a test case that isnt using Twisted since Ive no
idea what twisted does with threads. it looks like the result proxy
is being shared between threads (which i believe is an effect of the
twisted reactor anyway?).
if youre playing with threads to that degree the "threadlocal"
strategy may be too simplistic.
On Apr 9, 2007, at 5:41 PM, Manlio Perillo wrote:
>
> Hi.
>
> I have found some problems with threadlocal strategy and the
> ResultProxy.
>
> Here is the code that reproduces the problem, Twisted and
> PostgreSQL are
> required.
>
> I'm using SQLAlchemy 0.3.6-1 from Debian Etch.
>
> I don't know if this is a bug of SQLAlchemy.
> Is the ResultProxy thread safe?
>
>
>
> #! /usr/bin/env python
> import sys
>
> from twisted.python import log
> from twisted.internet import defer, threads, reactor
>
> import sqlalchemy as sq
>
>
> def callback(result, i):
> # Is the ResultProxy thread safe?
> if USE_CURSOR:
> rows = list(result)
>
> log.msg('callback', i)
>
> def errback(reason):
> log.err(reason)
>
> def f():
> l = []
>
> for i in range(N):
> log.msg('request', i)
> d = threads.deferToThread(db.execute, QUERY)
> d.addCallbacks(callback, errback, callbackArgs=(i,))
> l.append(d)
>
> return defer.DeferredList(l)
>
> def main():
> return f().addCallbacks(lambda _: None, lambda r: log.err(r)
> ).addBoth(lambda _: reactor.stop())
>
>
> POOL_SIZE = 1
> N = 10
> QUERY = 'SELECT CURRENT_TIMESTAMP'
> URL = 'postgres://manlio:[EMAIL PROTECTED]/test'
> STRATEGY = 'threadlocal'
> USE_CURSOR = False
>
>
> reactor.suggestThreadPoolSize(POOL_SIZE)
> db = sq.create_engine(URL, pool_size=POOL_SIZE, strategy=STRATEGY,
> echo_pool=False)
>
> log.startLogging(sys.stdout)
> reactor.callWhenRunning(main)
>
> reactor.run()
>
>
>
> When USE_CURSOR is False, I got (at random) the error:
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 718,
> in execute
> connection = self.contextual_connect
> (close_with_result=True)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/threadlocal.py",
> line 148, in contextual_connect
> return self.session.get_connection(**kwargs)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/threadlocal.py",
> line 21, in get_connection
> return TLConnection(self,
> close_with_result=close_with_result)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/threadlocal.py",
> line 63, in __init__
> base.Connection.__init__(self, session.engine,
> close_with_result=close_with_result)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 368,
> in __init__
> self.__connection = connection or engine.raw_connection()
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/threadlocal.py",
> line 127, in raw_connection
> return self.connection_provider.get_connection()
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/default.py", line
> 19, in get_connection
> return self._pool.connect()
> File "/usr/lib/python2.4/site-packages/sqlalchemy/pool.py",
> line 150, in connect
> return
> self._threadconns[thread.get_ident()].connfairy().checkout()
> exceptions.AttributeError: 'NoneType' object has no attribute
> 'checkout'
>
>
> When USE_CURSOR is True, I obtain (at random) any of these two errors:
> File "./concurrency.twisted.py", line 12, in callback
> rows = list(result)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 921,
> in __iter__
> row = self.fetchone()
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 997,
> in fetchone
> self.close()
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 862,
> in close
> self.cursor.close()
> File "/usr/lib/python2.4/site-packages/sqlalchemy/pool.py",
> line 312, in close
> if self in self.__parent._cursors:
> exceptions.TypeError: iterable argument required
>
>
> and:
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 719,
> in execute
> return connection.execute(statement, *multiparams,
> **params)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 444,
> in execute
> return Connection.executors[c](self, object,
> *multiparams,
> **params)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 458,
> in execute_text
> cursor = self._execute_raw(statement, parameters)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/engine/base.py", line
> 540,
> in _execute_raw
> cursor = self.__engine.dialect.create_cursor
> (self.connection)
> File
> "/usr/lib/python2.4/site-packages/sqlalchemy/databases/postgres.py",
> line 277, in create_cursor
> return connection.cursor()
> File "/usr/lib/python2.4/site-packages/sqlalchemy/pool.py",
> line 253, in cursor
> self.invalidate()
> File "/usr/lib/python2.4/site-packages/sqlalchemy/pool.py",
> line 243, in invalidate
> raise exceptions.InvalidRequestError("This connection is
> closed")
> sqlalchemy.exceptions.InvalidRequestError: This connection is
> closed
>
>
>
>
> Thanks and regards Manlio Perillo
>
>
> >
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