from twisted.internet import reactor, defer, threads

import sqlalchemy as sa

from exceptions import Exception

def _transact(engine):
    def _transaction(f):
        def _wrap(*args, **kwargs):
            def _1():
                conn = meta.engine.contextual_connect()
                trans = conn.begin()
                try:
                    r = f(*args, **kwargs)
                except Exception, e:
                    print e
                    trans.rollback()
                    conn.close()
                    raise
                else:
                    trans.commit()
                    conn.close()
                    return r
            return threads.deferToThread(_1)
        _wrap.__name__ = f.__name__
        return _wrap

    return _transaction

reactor.suggestThreadPoolSize(10)

meta = sa.DynamicMetaData(threadlocal = False)

users = sa.table('users',
        sa.Column('id', sa.Integer, primary_key = True),
        sa.Column('firstname', sa.String(128)),
        sa.Column('lastname', sa.String(128)),
        sa.Column('nickname', sa.String(128)),
        sa.Column('email', sa.String(255)),
    )

transact = _transact(meta)

sq = sa.create_engine("sqlite://./test.db")
meta.connect(sq)

@transact
def aa():
    users.insert().execute(firstname = "test",
                          lastname = "test",
                          nickname = "test",
                          email = "blah")

reactor.callLater(0.0, aa)
reactor.run()


Traceback :

Traceback (most recent call last):
  File "/usr/lib/python2.4/threading.py", line 422, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.4/site-packages/twisted/python/threadpool.py", line 148, in _worker
    context.call(ctx, function, *args, **kwargs)
  File "/usr/lib/python2.4/site-packages/twisted/python/context.py", line 59, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python2.4/site-packages/twisted/python/context.py", line 37, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "/usr/lib/python2.4/site-packages/twisted/internet/threads.py", line 25, in _putResultInDeferred
    result = f(*args, **kwargs)
  File "test.py", line 15, in _1
    r = f(*args, **kwargs)
  File "test.py", line 53, in aa
    email = "blah")
  File "/usr/lib/python2.4/site-packages/sqlalchemy/sql.py", line 509, in execute
    return self.execute_using(self.engine, *multiparams, **params)
  File "/usr/lib/python2.4/site-packages/sqlalchemy/sql.py", line 463, in execute_using
    return self.compile(engine=engine, parameters=compile_params).execute(*multiparams, **params)
  File "/usr/lib/python2.4/site-packages/sqlalchemy/sql.py", line 374, in execute
    raise exceptions.InvalidRequestError("This Compiled object is not bound to any engine.")
sqlalchemy.exceptions.InvalidRequestError: This Compiled object is not bound to any engine.