信号处理pika/python

我正在消费者中使用

pika.BlockingConnection

，该消费者为每条消息执行一些任务。我还添加了信号处理，以便消费者在完成所有任务后正确死亡

在处理消息和接收信号时，我只从函数中获取

“signal received”

，但代码不退出。所以，我决定检查在回调函数末尾接收到的信号。问题是，我需要检查信号多少次，因为代码中还有很多函数。有没有更好的方法来处理信号而不做过火的事情

import signal
import sys
import pika
from time import sleep

received_signal = False
all_over = False

def signal_handler(signal, frame):
    global received_signal
    print "signal received"
    received_signal = True

signal.signal(signal.SIGINT, signal_handler)
signal.signal(signal.SIGTERM, signal_handler)

mq_connection = pika.BlockingConnection(pika.ConnectionParameters(my_mq_server, virtual_host='test'))
mq_channel = mq_connection.channel()

def callback(ch, method, properties, body):
    if received_signal:
        print "Exiting, as a kill signal is already received"
        exit(0)
    print body
    sleep(50)
    mq_channel.basic_ack(delivery_tag=method.delivery_tag)
    print "Message consumption complete"

    if received_signal:
        print "Exiting, as a kill signal is already received"
        exit(0)

try:
    print ' [*] Waiting for messages. To exit press CTRL+C'
    mq_channel.basic_consume(callback, queue='test')
    mq_channel.start_consuming()
except Exception:
    mq_channel.close()
    exit()

---

这是我在这里的第一个问题，如果需要更多详细信息，请告诉我。

我想这正是您想要的：

#!/usr/bin/python

import signal
import sys 
import pika
from contextlib import contextmanager

received_signal = False
processing_callback = False

def signal_handler(signal, frame):
    global received_signal
    print "signal received"
    received_signal = True
    if not processing_callback:
         sys.exit()

signal.signal(signal.SIGINT, signal_handler)
signal.signal(signal.SIGTERM, signal_handler)

@contextmanager
def block_signals():
    global processing_callback
    processing_callback = True
    try:
        yield
    finally:
        processing_callback = False
        if received_signal:
            sys.exit()

def callback(ch, method, properties, body):
    with block_signals:
        print body
        sum(xrange(0, 200050000)) # sleep gets interrupted by signals, this doesn't.
        mq_channel.basic_ack(delivery_tag=method.delivery_tag)
        print "Message consumption complete"

if __name__ == "__main__":    
    try:
        mq_connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
        mq_channel = mq_connection.channel()
        print ' [*] Waiting for messages. To exit press CTRL+C'
        mq_channel.basic_consume(callback, queue='test')
        mq_channel.start_consuming()
    except Exception as e:
        mq_channel.close()
        sys.exit()

我使用了contextmanager来处理阻塞信号，因此所有逻辑都隐藏在回调本身之外。这也会使代码的重用变得更容易。为了说明它是如何工作的，它相当于：

def callback(ch, method, properties, body):
    global processing_callback
    processing_callback = True
    try:
        print body
        sum(xrange(0, 200050000))
        mq_channel.basic_ack(delivery_tag=method.delivery_tag)
        print "Message consumption complete"
    finally:
        processing_callback = False
        if received_signal:
            sys.exit()

---

当前代码将吞下SIGTERM或SIGINT，直到通过队列接收到下一条消息，此时它应该退出。这真的是你想要的吗？为什么不让

signal\u handler

方法直接调用

sys.exit（0）

呢？我希望信号处理可以通过两种方式完成：1）在等待消息时，它应该死掉；2）在使用消息时，它应该完成当前的工作，然后死掉。我当前的代码包含第二个条件，但不是第一个条件。这就是问题所在。这有可能吗？是的，有可能。我将添加一个答案。使用xrange而不是range，否则您的内存将爆炸，当它翻页到磁盘时，它将开始颠簸。