--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/iro/model/utils.py	Sun Jan 22 23:29:18 2012 +0100
@@ -0,0 +1,49 @@
+from sqlalchemy.orm import sessionmaker
+
+from twisted.internet import reactor
+from twisted.internet import threads
+from twisted.python.threadpool import ThreadPool
+
+POOL_SIZE=5     #how many threads should the db connector pool should have
+
+dbpool = ThreadPool(minthreads=1, maxthreads=POOL_SIZE, name='database')
+dbpool.start()
+reactor.addSystemEventTrigger('before', 'shutdown', dbpool.stop)
+
+def run_in_db_thread(f):
+    """Decorator to run DB queries in Twisted's thread pool"""
+    def wrapper(*args, **kwargs):
+        return threads.deferToThreadPool(reactor, dbpool,f, *args, **kwargs)
+    return wrapper
+
+
+class WithSession(object):
+    '''a with statement for a database session connection'''
+    def __init__(self, engine, autocommit=False):
+        self.engine = engine
+        self.autocommit=autocommit
+    
+    def __enter__(self):
+        self.session = sessionmaker(bind=self.engine)()
+        return self.session
+    
+    def __exit__(self,exc_type, exc_value, traceback):
+        if exc_type is None:
+            if self.autocommit:
+                self.session.commit()
+        else:
+            self.session.rollback()
+        self.session.close()
+
+class DBDefer(object):
+    '''a twisted sqlalchemy connector this Decorator adds a session parameter, with a valid session connection'''
+    def __init__(self, engine, autocommit=False):
+        self.autocommit=autocommit
+        self.engine = engine
+
+    def __call__(self, func):
+        @run_in_db_thread
+        def wrapper(*args, **kwargs):
+            with WithSession(self.engine, self.autocommit) as session:
+                return func(*args, session=session, **kwargs)
+        return wrapper