-
Notifications
You must be signed in to change notification settings - Fork 3
/
aconsumer.py
388 lines (300 loc) · 15.7 KB
/
aconsumer.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
# -*- coding: utf-8 -*-
import logging
import pika
# All changes to the example consumer class are marked with !!
# !! If logging is not started in the main program, uncomment these lines.
# LOG_FORMAT = ('%(levelname) -10s %(asctime)s %(name) -30s %(funcName) '
# '-35s %(lineno) -5d: %(message)s')
LOGGER = logging.getLogger(__name__)
class Consumer(object):
"""This is an example consumer that will handle unexpected interactions
with RabbitMQ such as channel and connection closures.
If RabbitMQ closes the connection, it will reopen it. You should
look at the output, as there are limited reasons why the connection may
be closed, which usually are tied to permission related issues or
socket timeouts.
If the channel is closed, it will indicate a problem with one of the
commands that were issued and that should surface in the output as well.
"""
EXCHANGE = 'message'
EXCHANGE_TYPE = 'topic'
# QUEUE = 'text' # !! We don't hard-code the name of the queue.
ROUTING_KEY = 'example.text'
def __init__(self, amqp_url):
"""Create a new instance of the consumer class, passing in the AMQP
URL used to connect to RabbitMQ.
:param str amqp_url: The AMQP url to connect with
"""
self._connection = None
self._channel = None
self._closing = False
self._consumer_tag = None
self._url = amqp_url
# !! The following six object data members are new.
self._queue = None
self._on_message_callback = None # Use a callback to process the message.
self._message_count = 0 # Count messages and failed messages.
self._failed_message_count = 0 #
self._message_count_limit = 0 # Stop reading messages after reading this many.
self._acknowledge_messages = True # Whether to send ack upon receiving message
# !! The following four methods are new
def set_acknowledge_messages(self, true_or_false) :
"""When set to True, messages are acknowledged after reading.
When set to False, no acknowledgment is sent.
"""
self._acknowledge_messages = true_or_false
def set_queue(self, queue) :
self._queue = queue
def add_on_message_callback(self, on_message_callback) :
self._on_message_callback = on_message_callback
def set_message_count_limit(self, message_count_limit) :
self._message_count_limit = message_count_limit
def connect(self):
"""This method connects to RabbitMQ, returning the connection handle.
When the connection is established, the on_connection_open method
will be invoked by pika.
:rtype: pika.SelectConnection
"""
LOGGER.info('Connecting to %s', self._url)
return pika.SelectConnection(pika.URLParameters(self._url),
self.on_connection_open,
self.on_connection_error, # !! Handle error opening connection
stop_ioloop_on_close=False)
def on_connection_open(self, unused_connection):
"""This method is called by pika once the connection to RabbitMQ has
been established. It passes the handle to the connection object in
case we need it, but in this case, we'll just mark it unused.
:type unused_connection: pika.SelectConnection
"""
LOGGER.info('Connection opened')
self.add_on_connection_close_callback()
self.open_channel()
def on_connection_error(self, unused_connection, message): # !! New method
"""This method is called by pika if the connection to RabbitMQ has
failed to be established. It passes the handle to the connection object in
case we need it, but in this case, we'll just mark it unused.
:type unused_connection: pika.SelectConnection
"""
LOGGER.error('Connection failed: %s', message)
def add_on_connection_close_callback(self):
"""This method adds an on close callback that will be invoked by pika
when RabbitMQ closes the connection to the publisher unexpectedly.
"""
LOGGER.info('Adding connection close callback')
self._connection.add_on_close_callback(self.on_connection_closed)
def on_connection_closed(self, connection, reply_code, reply_text):
"""This method is invoked by pika when the connection to RabbitMQ is
closed unexpectedly. Since it is unexpected, we will reconnect to
RabbitMQ if it disconnects.
:param pika.connection.Connection connection: The closed connection obj
:param int reply_code: The server provided reply_code if given
:param str reply_text: The server provided reply_text if given
"""
self._channel = None
if self._closing:
self._connection.ioloop.stop()
else:
LOGGER.warning('Connection closed, reopening in 5 seconds: (%s) %s',
reply_code, reply_text)
self._connection.add_timeout(5, self.reconnect)
def reconnect(self):
"""Will be invoked by the IOLoop timer if the connection is
closed. See the on_connection_closed method.
"""
# This is the old connection IOLoop instance, stop its ioloop
self._connection.ioloop.stop()
if not self._closing:
# Create a new connection
self._connection = self.connect()
# There is now a new connection, needs a new ioloop to run
self._connection.ioloop.start()
def open_channel(self):
"""Open a new channel with RabbitMQ by issuing the Channel.Open RPC
command. When RabbitMQ responds that the channel is open, the
on_channel_open callback will be invoked by pika.
"""
LOGGER.info('Creating a new channel')
self._connection.channel(on_open_callback=self.on_channel_open)
def on_channel_open(self, channel):
"""This method is invoked by pika when the channel has been opened.
The channel object is passed in so we can make use of it.
Since the channel is now open, we'll declare the exchange to use.
:param pika.channel.Channel channel: The channel object
"""
LOGGER.info('Channel opened')
self._channel = channel
self.add_on_channel_close_callback()
self.setup_exchange(self.EXCHANGE)
def add_on_channel_close_callback(self):
"""This method tells pika to call the on_channel_closed method if
RabbitMQ unexpectedly closes the channel.
"""
LOGGER.info('Adding channel close callback')
self._channel.add_on_close_callback(self.on_channel_closed)
def on_channel_closed(self, channel, reply_code, reply_text):
"""Invoked by pika when RabbitMQ unexpectedly closes the channel.
Channels are usually closed if you attempt to do something that
violates the protocol, such as re-declare an exchange or queue with
different parameters. In this case, we'll close the connection
to shutdown the object.
:param pika.channel.Channel: The closed channel
:param int reply_code: The numeric reason the channel was closed
:param str reply_text: The text reason the channel was closed
"""
LOGGER.warning('Channel %i was closed: (%s) %s',
channel, reply_code, reply_text)
self._connection.close()
def setup_exchange(self, exchange_name):
"""Setup the exchange on RabbitMQ by invoking the Exchange.Declare RPC
command. When it is complete, the on_exchange_declareok method will
be invoked by pika.
:param str|unicode exchange_name: The name of the exchange to declare
"""
LOGGER.info('Declaring exchange %s', exchange_name)
self._channel.exchange_declare(self.on_exchange_declareok,
exchange_name,
self.EXCHANGE_TYPE)
def on_exchange_declareok(self, unused_frame):
"""Invoked by pika when RabbitMQ has finished the Exchange.Declare RPC
command.
:param pika.Frame.Method unused_frame: Exchange.DeclareOk response frame
"""
LOGGER.info('Exchange declared')
self.setup_queue(self._queue)
def setup_queue(self, queue_name):
"""Setup the queue on RabbitMQ by invoking the Queue.Declare RPC
command. When it is complete, the on_queue_declareok method will
be invoked by pika.
:param str|unicode queue_name: The name of the queue to declare.
"""
LOGGER.info('Declaring queue %s', queue_name)
self._channel.queue_declare(self.on_queue_declareok, queue_name)
def on_queue_declareok(self, method_frame):
"""Method invoked by pika when the Queue.Declare RPC call made in
setup_queue has completed. In this method we will bind the queue
and exchange together with the routing key by issuing the Queue.Bind
RPC command. When this command is complete, the on_bindok method will
be invoked by pika.
:param pika.frame.Method method_frame: The Queue.DeclareOk frame
"""
LOGGER.info('Binding %s to %s with %s',
self.EXCHANGE, self._queue, self.ROUTING_KEY)
self._channel.queue_bind(self.on_bindok, self._queue,
self.EXCHANGE, self.ROUTING_KEY)
def on_bindok(self, unused_frame):
"""Invoked by pika when the Queue.Bind method has completed. At this
point we will start consuming messages by calling start_consuming
which will invoke the needed RPC commands to start the process.
:param pika.frame.Method unused_frame: The Queue.BindOk response frame
"""
LOGGER.info('Queue bound')
self.start_consuming()
def start_consuming(self):
"""This method sets up the consumer by first calling
add_on_cancel_callback so that the object is notified if RabbitMQ
cancels the consumer. It then issues the Basic.Consume RPC command
which returns the consumer tag that is used to uniquely identify the
consumer with RabbitMQ. We keep the value to use it when we want to
cancel consuming. The on_message method is passed in as a callback pika
will invoke when a message is fully received.
"""
LOGGER.info('Issuing consumer related RPC commands')
self.add_on_cancel_callback()
self._consumer_tag = self._channel.basic_consume(self.on_message,
self._queue)
def add_on_cancel_callback(self):
"""Add a callback that will be invoked if RabbitMQ cancels the consumer
for some reason. If RabbitMQ does cancel the consumer,
on_consumer_cancelled will be invoked by pika.
"""
LOGGER.info('Adding consumer cancellation callback')
self._channel.add_on_cancel_callback(self.on_consumer_cancelled)
def on_consumer_cancelled(self, method_frame):
"""Invoked by pika when RabbitMQ sends a Basic.Cancel for a consumer
receiving messages.
:param pika.frame.Method method_frame: The Basic.Cancel frame
"""
LOGGER.info('Consumer was cancelled remotely, shutting down: %r',
method_frame)
if self._channel:
self._channel.close()
def on_message(self, unused_channel, basic_deliver, properties, body):
"""Invoked by pika when a message is delivered from RabbitMQ. The
channel is passed for your convenience. The basic_deliver object that
is passed in carries the exchange, routing key, delivery tag and
a redelivered flag for the message. The properties passed in is an
instance of BasicProperties with the message properties and the body
is the message that was sent.
:param pika.channel.Channel unused_channel: The channel object
:param pika.Spec.Basic.Deliver: basic_deliver method
:param pika.Spec.BasicProperties: properties
:param str|unicode body: The message body
"""
# !! In the original example, the message is simply logged.
# LOGGER.info('Received message # %s from %s: %s',
# basic_deliver.delivery_tag, properties.app_id, body)
num = self._on_message_callback(unused_channel, basic_deliver, properties, body)
if self._acknowledge_messages :
self.acknowledge_message(basic_deliver.delivery_tag)
self._message_count = self._message_count + 1
if num == 0:
self._failed_message_count = self._failed_message_count + 1
LOGGER.info('Processed %d messages. %d failed messages', self._message_count, self._failed_message_count)
if self._message_count_limit > 0 and self._message_count >= self._message_count_limit :
LOGGER.info('Processed limit of %d messages. %d failed messages', self._message_count, self._failed_message_count)
self.stop()
def acknowledge_message(self, delivery_tag):
"""Acknowledge the message delivery from RabbitMQ by sending a
Basic.Ack RPC method for the delivery tag.
:param int delivery_tag: The delivery tag from the Basic.Deliver frame
"""
LOGGER.info('Acknowledging message %s', delivery_tag)
self._channel.basic_ack(delivery_tag)
def stop_consuming(self):
"""Tell RabbitMQ that you would like to stop consuming by sending the
Basic.Cancel RPC command.
"""
if self._channel:
LOGGER.info('Sending a Basic.Cancel RPC command to RabbitMQ')
self._channel.basic_cancel(self.on_cancelok, self._consumer_tag)
def on_cancelok(self, unused_frame):
"""This method is invoked by pika when RabbitMQ acknowledges the
cancellation of a consumer. At this point we will close the channel.
This will invoke the on_channel_closed method once the channel has been
closed, which will in-turn close the connection.
:param pika.frame.Method unused_frame: The Basic.CancelOk frame
"""
LOGGER.info('RabbitMQ acknowledged the cancellation of the consumer')
self.close_channel()
def close_channel(self):
"""Call to close the channel with RabbitMQ cleanly by issuing the
Channel.Close RPC command.
"""
LOGGER.info('Closing the channel')
self._channel.close()
def run(self):
"""Run the example consumer by connecting to RabbitMQ and then
starting the IOLoop to block and allow the SelectConnection to operate.
"""
self._connection = self.connect()
self._connection.ioloop.start()
def stop(self):
"""Cleanly shutdown the connection to RabbitMQ by stopping the consumer
with RabbitMQ. When RabbitMQ confirms the cancellation, on_cancelok
will be invoked by pika, which will then closing the channel and
connection. The IOLoop is started again because this method is invoked
when CTRL-C is pressed raising a KeyboardInterrupt exception. This
exception stops the IOLoop which needs to be running for pika to
communicate with RabbitMQ. All of the commands issued prior to starting
the IOLoop will be buffered but not processed.
"""
LOGGER.info('Stopping')
LOGGER.info('Processed %d messages. %d failed messages', self._message_count, self._failed_message_count)
self._closing = True
self.stop_consuming()
self._connection.ioloop.start()
LOGGER.info('Stopped')
def close_connection(self):
"""This method closes the connection to RabbitMQ."""
LOGGER.info('Closing connection')
self._connection.close()