Consumer using connection pools which only pops one element

# This code results in only one element being consumed from the queue, do you know what's wrong?

from kombu import  Exchange, Queue, BrokerConnection, pools

EXCHANGE_ID = 'queued-requests'
EXCHANGE_TYPE = 'direct'
QUEUE_ID = EXCHANGE_ID
ROUTING_KEY = EXCHANGE_ID
CONNECTION_URI = 'amqp://guest:guest@localhost//'
SERIALIZED_FORMAT='pickle'

DEFAULT_CONNECTION_POOL_SIZE = 16

exchange = Exchange(EXCHANGE_ID, EXCHANGE_TYPE, durable=True)
queue = Queue(QUEUE_ID, exchange=exchange, routing_key=ROUTING_KEY)
broker_connection = BrokerConnection(CONNECTION_URI)
queue_connections = pools.Connections(limit=DEFAULT_CONNECTION_POOL_SIZE)


def on_error(m, exc):
    print "Error decoding message: %s", exc

def on_message(m):
    m.ack()
    print "Message received"

while True:
    try:
        print "Getting into consumer loop"
        with queue_connections[broker_connection].acquire(block=True) as consumer_connection:
            with consumer_connection.Consumer(queue, on_message=on_message,
                                              on_decode_error=on_error, accept=[SERIALIZED_FORMAT]) as consumer:
                print "Calling drain events, connection", consumer_connection,  "consumer",  consumer
                consumer_connection.drain_events()
    except Exception, e:
            print "Error while attempting to consume from queue", e