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#!/usr/bin/env python
"""
topic_subscriber.py
This subscriber creates private queues and binds them
to the topics "usa.#", "europe.#", "#.news", and "#.weather".
"""
import base64
import qpid
from qpid.client import Client
from qpid.content import Content
from qpid.queue import Empty
#----- Functions -------------------------------------------
def dump_queue(client, queue_name):
print "Messages queue: " + queue_name
consumer_tag = queue_name # Use the queue name as the consumer tag - need a unique tag
queue = client.queue(consumer_tag)
# Call basic_consume() to tell the broker to deliver messages
# from the AMQP queue to a local client queue. The broker will
# start delivering messages as soon as basic_consume() is called.
session.message_subscribe(queue=queue_name, destination=consumer_tag)
session.message_flow(consumer_tag, 0, 0xFFFFFFFF)
session.message_flow(consumer_tag, 1, 0xFFFFFFFF)
content = "" # Content of the last message read
final = "That's all, folks!" # In a message body, signals the last message
message = 0
while content != final:
try:
message = queue.get()
content = message.content.body
print content
except Empty:
if message != 0:
message.complete(cumulative=True)
print "No more messages!"
return
# Messages are not removed from the queue until they
# are acknowledged. Using multiple=True, all messages
# in the channel up to and including the one identified
# by the delivery tag are acknowledged. This is more efficient,
# because there are fewer network round-trips.
if message != 0:
message.complete(cumulative=True)
#----- Initialization --------------------------------------
# Set parameters for login
host="127.0.0.1"
port=5672
amqp_spec="/usr/share/amqp/amqp.0-10-preview.xml"
user="guest"
password="guest"
# Create a client and log in to it.
spec = qpid.spec.load(amqp_spec)
client = Client(host, port, spec)
client.start({"LOGIN": user, "PASSWORD": password})
session = client.session()
session_info = session.session_open()
session_id = session_info.session_id
#----- Main Body -- ----------------------------------------
news = "news" + base64.urlsafe_b64encode(session_id)
weather = "weather" + base64.urlsafe_b64encode(session_id)
usa = "usa" + base64.urlsafe_b64encode(session_id)
europe = "europe" + base64.urlsafe_b64encode(session_id)
session.queue_declare(queue=news, exclusive=True)
session.queue_declare(queue=weather, exclusive=True)
session.queue_declare(queue=usa, exclusive=True)
session.queue_declare(queue=europe, exclusive=True)
# Routing keys may be "usa.news", "usa.weather", "europe.news", or "europe.weather".
# The '#' symbol matches one component of a multipart name, e.g. "#.news" matches
# "europe.news" or "usa.news".
session.queue_bind(exchange="amq.topic", queue=news, routing_key="#.news")
session.queue_bind(exchange="amq.topic", queue=weather, routing_key="#.weather")
session.queue_bind(exchange="amq.topic", queue=usa, routing_key="usa.#")
session.queue_bind(exchange="amq.topic", queue=europe, routing_key="europe.#")
# Bind each queue to the control queue so we know when to stop
session.queue_bind(exchange="amq.topic", queue=news, routing_key="control")
session.queue_bind(exchange="amq.topic", queue=weather, routing_key="control")
session.queue_bind(exchange="amq.topic", queue=usa, routing_key="control")
session.queue_bind(exchange="amq.topic", queue=europe, routing_key="control")
# Remind the user to start the topic producer
print "Queues create - please start the topic producer"
# Call dump_queue to print messages from each queue
dump_queue(client, news)
dump_queue(client, weather)
dump_queue(client, usa)
dump_queue(client, europe)
#----- Cleanup ------------------------------------------------
# Clean up before exiting so there are no open threads.
session.session_close()
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