green polling to wait for notify

Hello,

I am using the great new coroutine feature to integrate eventlet with psycopg2. I wrote the following code to run a greenlet thread which merely waits for a NOTIFY event.

def postgresql_listen(connect_string):
    dbconn = psycopg2.connect(connect_string)
    #issue listen for events                                                                                                 
    dbconn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
    dbcursor = dbconn.cursor()
    dbcursor.execute('LISTEN test;');
    dbcursor.close()
    while True:
        print 'poll in'
        state = dbconn.poll()
        print 'poll out'
        if state == psycopg2.extensions.POLL_OK:
            while dbconn.notifies:
                notification = dbconn.notifies.pop()
                print notification
            select.select([dbconn.fileno()], [], []) #delete this line to cause infinite loop- I had to add this line to prevent it
        elif state == psycopg2.extensions.POLL_READ:
            select.select([dbconn.fileno()], [], [])
        elif state == psycopg2.extensions.POLL_WRITE:
            select.select([], [dbconn.fileno()], [])
        else:
            raise OperationalError("bad state from poll: %s" % state)

I am mimicking the documentation's approach to asynchronous polling- why does poll() always return POLL_OK in this case?

Is there a cleaner way to simply block for asynchronous events?

Cheers,
M