rabbitmq消息消费
消费方法
Basic.Get
- 每次接收消息必须发送一次请求
- 有消息可用,RabbitMQ返回Basic.GetOk以及消息
- 无消息可用,RabbitMQ返回Basic.GetEmpty 应用程序需要评估RPC响应以及是否接收到消息。
示例程序
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'test-messages')
queue.declare()
while True:
message = queue.get()
if message:
message.pprint()
# 确认消息
message.ack()
if message.body == 'stop':
break
Basic.Consume
- 消费者可用时,异步方式发送消息
- 应用程序自动接收消息,直到Basic.Cancel
- 仍然需要确认消息
示例程序
import rabbitpy
for message in rabbitpy.consume('amqp://guest:guest@localhost:5672/%2f',
'test-messages'):
message.pprint()
# 消息确认
message.ack()
消费者标签
应用程序发出Basic.Comsume时,创建唯一字符串(消费者标签),标识应用程序。RabbitMQ每次都会把该字符串和消息一同发送给应用程序。
客户端库对消费者标签封装,以确定如何处理消息。开发者不用处理消费者标签。
示例代码:监听消息直到,收到停止消息
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
for message in rabbitpy.Queue(channel, 'test-messages'):
message.pprint()
message.ack()
if message.body == 'stop':
break
对比
Consume吞吐量更大。Get包含了每条消息的同步通信开销。
消费性能优化
1、no-ack
应用程序发送Basic.Comsume请求时,设置no-ack。表明消费者不进行消费确认。
示例代码:消费不确认
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'test-messages')
for message in queue.consume_messages(no_ack=True):
message.pprint()
2、预取
QoS(Quality of service)中,可设置消费者预先接收一定数量的消息。Basic.Qos一般在Basic.Consume之前设置。
示例程序:指定QoS
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
#预取数为10
channel.prefetch_count(10)
for message in rabbitpy.Queue(channel, 'test-messages'):
message.pprint()
message.ack()
应用程序不需要确认每条消息,可确认所有以前未读消息。
示例程序:多消息确认
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
channel.prefetch_count(10)
for message in rabbitpy.Queue(channel, 'test-messages'):
message.pprint()
unacknowledged += 1
if unacknowledged == 10:
# 确认所有未确认消息
message.ack(all_previous=True)
unacknowledged = 0
3、事务
事务允许消费者应用程序提交和回滚批量操作。不适用QoS时,可以获得轻微的性能提升。
拒绝消息
Basic.Reject
通知rabbitmq无法处理投递的消息(拒绝一个消息),可指示rabbitMQ丢弃消息或使用requeue重发消息。
示例程序:消息拒绝
import rabbitpy
for message in rabbitpy.consume('amqp://guest:guest@localhost:5672/%2f',
'test-messages'):
message.pprint()
print('Redelivered: %s' % message.redelivered)
message.reject(True)
Basic.Nack
同时拒绝多个消息
死信交换器(DLX)
创建队列时声明该交换器用于保存被拒绝的消息。队列x-dead-letter-exchange参数(RPC请求)指定死信交换器。
示例程序:指定死信交换器
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
#死信交换器
rabbitpy.Exchange(channel, 'rejected-messages').declare()
queue = rabbitpy.Queue(channel, 'dlx-example',
dead_letter_exchange='rejected-messages')
queue.declare()
控制队列
临时队列
自动删除队列
消费者完成连接和检索消息,所有消费者断开连接时,队列将被删除。
示例程序:自动删除队列auto_delete=True
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'ad-example', auto_delete=True)
queue.declare()
只允许单个消费者
只有单个消费者能够消费队列中的消息。消费者断开连接后,会自动删除队列。
示例程序:独占队列exclusive
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'exclusive-example',
exclusive=True)
queue.declare()
自动过期队列
如果一段时间没有使用该队列就删除它,一般用于RPC回复队列。
示例程序:自动过期队列
import rabbitpy
import time
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'expiring-queue',
arguments={'x-expires': 1000})
queue.declare()
messages, consumers = queue.declare(passive=True)
time.sleep(2)
try:
messages, consumers = queue.declare(passive=True)
except rabbitpy.exceptions.AMQPNotFound:
print('The queue no longer exists')
永久队列
队列持久性
服务器重启后队列仍然存在。
示例程序:持久队列
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'durable-queue',
durable=True)
if queue.declare():
print('Queue declared')
队列消息自动过期
同时指定死信交换器和消息TTL,过期消息将成为死信消息。
示例程序:消息TTL
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'expiring-msg-queue',
arguments={'x-message-ttl': 1000})
queue.declare()
最大队列长度
一旦达到最大值,添加新消息时,删除队列前端的消息。声明队列时,如果指定死信交换器,前端移除的消息将成为死信。
示例程序:最大长度队列
import rabbitpy
with rabbitpy.Connection() as connection:
with connection.channel() as channel:
queue = rabbitpy.Queue(channel, 'max-length-queue',
arguments={'x-max-length': 1000})
queue.declare()
队列设置参数
参数 | 说明 |
---|---|
x-dead-letter-exchange | 死信交换器,路由不重发且被拒绝的消息 |
x-dead-letter-routing-key | 死信消息的可选路由键 |
x-expires | 队列在指定的毫秒数后删除 |
x-ha-proxy | 创建HA队列 |
x-ha-nodes | HA队列分布的节点 |
x-max-length | 队列的最大消息数 |
x-message-ttl | 毫秒为单位的队列过期时间 |
x-max-priority | 队列优先级排序 |
posted on 2020-10-05 15:26 hainingwyx 阅读(1458) 评论(0) 编辑 收藏 举报