class Consumer(object):
""" A message consumer """
topic = None
# Automatically decode JSON data
jsonify = True
def __init__(self):
self.hub = MokshaHub()
self.log = log
if self.hub.amqp_broker and not self.hub.stomp_broker:
for topic in listify(self.topic):
log.debug('Subscribing to consumer topic %s' % topic)
if isinstance(self.hub, AMQPLibHub):
# AMQPLibHub specific
queue_name = str(uuid.uuid4())
self.hub.queue_declare(queue=queue_name, exclusive=True)
self.hub.exchange_bind(queue_name, binding_key=topic)
if self.jsonify:
self.hub.queue_subscribe(queue_name, self._consume_json)
else:
self.hub.queue_subscribe(queue_name, self._consume)
else:
# Assume we're using Qpid then.
server_queue_name = 'moksha_consumer_' + self.hub.session.name
self.hub.queue_declare(queue=server_queue_name, exclusive=True)
self.hub.exchange_bind(server_queue_name, binding_key=topic)
local_queue_name = 'moksha_consumer_' + self.hub.session.name
self.hub.local_queue = self.hub.session.incoming(local_queue_name)
self.hub.message_subscribe(queue=server_queue_name,
destination=local_queue_name)
self.hub.local_queue.start()
if self.jsonify:
self.hub.local_queue.listen(self._consume_json)
else:
self.hub.local_queue.listen(self._consume)
# If the consumer specifies an 'app', then setup `self.engine` to
# be a SQLAlchemy engine, along with a configured DBSession
app = getattr(self, 'app', None)
self.engine = self.DBSession = None
if app:
log.debug("Setting up individual engine for consumer")
self.engine = create_app_engine(app)
self.DBSession = sessionmaker(bind=self.engine)()
def _consume_json(self, message):
""" Convert our AMQP messages into a consistent dictionary format.
This method exists because our STOMP & AMQP message brokers consume
messages in different formats. This causes our messaging abstraction
to leak into the consumers themselves.
:Note: We do not pass the message headers to the consumer (in this AMQP consumer)
because the current AMQP.js bindings do not allow the client to change them.
Thus, we need to throw any topic/queue details into the JSON body itself.
"""
try:
body = json.decode(message.body)
except:
log.debug("Unable to decode message body to JSON: %r" % message.body)
body = message.body
topic = None
try:
topic = message.headers[0].routing_key
except TypeError:
# We didn't get a JSON dictionary
pass
except AttributeError:
# We didn't get headers or a routing key?
pass
self.consume({'body': body, 'topic': topic})
def _consume(self, message):
self.consume(message)
def consume(self, message):
raise NotImplementedError
def send_message(self, topic, message):
try:
self.hub.send_message(topic, message, jsonify=self.jsonify)
except Exception, e:
log.error('Cannot send message: %s' % e)
class Consumer(object):
""" A message consumer """
topic = None
# Automatically decode JSON data
jsonify = True
def __init__(self):
self.hub = MokshaHub()
self.log = log
if self.hub.amqp_broker and not self.hub.stomp_broker:
for topic in listify(self.topic):
log.debug('Subscribing to consumer topic %s' % topic)
if isinstance(self.hub, AMQPLibHub):
# AMQPLibHub specific
queue_name = str(uuid.uuid4())
self.hub.queue_declare(queue=queue_name, exclusive=True)
self.hub.exchange_bind(queue_name, binding_key=topic)
if self.jsonify:
self.hub.queue_subscribe(queue_name,
self._consume_json)
else:
self.hub.queue_subscribe(queue_name, self._consume)
else:
# Assume we're using Qpid then.
server_queue_name = 'moksha_consumer_' + self.hub.session.name
self.hub.queue_declare(queue=server_queue_name,
exclusive=True)
self.hub.exchange_bind(server_queue_name,
binding_key=topic)
local_queue_name = 'moksha_consumer_' + self.hub.session.name
self.hub.local_queue = self.hub.session.incoming(
local_queue_name)
self.hub.message_subscribe(queue=server_queue_name,
destination=local_queue_name)
self.hub.local_queue.start()
if self.jsonify:
self.hub.local_queue.listen(self._consume_json)
else:
self.hub.local_queue.listen(self._consume)
# If the consumer specifies an 'app', then setup `self.engine` to
# be a SQLAlchemy engine, along with a configured DBSession
app = getattr(self, 'app', None)
self.engine = self.DBSession = None
if app:
log.debug("Setting up individual engine for consumer")
self.engine = create_app_engine(app)
self.DBSession = sessionmaker(bind=self.engine)()
def _consume_json(self, message):
""" Convert our AMQP messages into a consistent dictionary format.
This method exists because our STOMP & AMQP message brokers consume
messages in different formats. This causes our messaging abstraction
to leak into the consumers themselves.
:Note: We do not pass the message headers to the consumer (in this AMQP consumer)
because the current AMQP.js bindings do not allow the client to change them.
Thus, we need to throw any topic/queue details into the JSON body itself.
"""
try:
body = json.decode(message.body)
except:
log.debug("Unable to decode message body to JSON: %r" %
message.body)
body = message.body
topic = None
try:
topic = message.headers[0].routing_key
except TypeError:
# We didn't get a JSON dictionary
pass
except AttributeError:
# We didn't get headers or a routing key?
pass
self.consume({'body': body, 'topic': topic})
def _consume(self, message):
self.consume(message)
def consume(self, message):
raise NotImplementedError
def send_message(self, topic, message):
try:
self.hub.send_message(topic, message, jsonify=self.jsonify)
except Exception, e:
log.error('Cannot send message: %s' % e)
