信号处理pika/python

Question

我pika.BlockingConnection在消费者中使用,为每条消息执行一些任务.我还添加了信号处理功能,以便消费者在完成所有任务后正常死亡.

在处理消息并收到信号时,我只是"signal received"从函数中获取,但代码不会退出.所以,我决定检查在回调函数结束时收到的信号.问题是,我检查信号的次数是多少,因为此代码中还有更多的功能.是否有更好的处理信号的方法而不会过度使用东西？

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()

这是我的第一个问题,如果需要更多细节,请告诉我.

Answer 1

我认为这符合您的要求：

#!/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()

我使用上下文管理器来处理阻塞信号，以便所有逻辑都隐藏在回调本身之外。这也将使代码的重用变得更加容易。只是为了澄清它是如何工作的，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()