listen / notify

Output when connected to 9.2.8 without "problems":
-------------------------------------------------
LISTEN data_0
LISTEN data_1
LISTEN data_2
LISTEN data_3
LISTEN data_4
LISTEN data_5
LISTEN data_6
LISTEN data_7
LISTEN data_8
LISTEN data_9

1: POLL_OK

2: POLL_OK

3: POLL_OK
[Notify(20218, 'data_2', ''), Notify(20218, 'data_3', ''), Notify(20218, 'data_1', '')]
3: data_1
[Notify(20218, 'data_2', ''), Notify(20218, 'data_3', '')]
3: data_3
[Notify(20218, 'data_2', '')]
3: data_2

4: POLL_OK


Output when connected to 9.2.8 with "problems":
---------------------------------------------

LISTEN data_0
LISTEN data_1
LISTEN data_2
LISTEN data_3
LISTEN data_4
LISTEN data_5
LISTEN data_6
LISTEN data_7
LISTEN data_8
LISTEN data_9
1: POLL_OK

2: POLL_OK

3: POLL_OK
[Notify(30642, 'data_2', '')]
3: data_2

4: POLL_OK
[Notify(30642, 'data_3', '')]
4: data_3

5: POLL_OK
[Notify(30642, 'data_1', '')]
5: data_1

6: POLL_OK


Python test script
------------------

#!/usr/bin/env python
import psycopg2,time
from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT

dsn = "host=host dbname=database user=username"

cnn = psycopg2.connect(dsn)
cnn.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
cur = cnn.cursor()

for x in range(0, 10):
    sql = "LISTEN data_" + str(x)
    cur.execute(sql)
    print sql

id=1

while 1:

    while 1:
        state = cnn.poll()
        if state == psycopg2.extensions.POLL_OK:
            print str(id) + ": POLL_OK"
            break
        elif state == psycopg2.extensions.POLL_READ:
            select.select([conn.fileno()], [], [])
            print str(id) + ": POLL READ"
        else:
            raise psycopg2.OperationalError("poll() returned %s" % state)

    while cnn.notifies:
        print str(id)
        print cnn.notifies

        n = cnn.notifies.pop().channel

        print str(id) + ': ' + n
        time.sleep(2)

    print "\n"
    time.sleep(2)
    id = id +1