python - 值错误: signal only works in main thread when using Stomp

Question

当我运行此代码时，出现此错误:

ValueError: signal only works in main thread

我正在使用 ActiveMQ。

RealTor 是我的 Spider(selogerSpider) 的名称，它可以帮助我进行抓取。

import stomp
from RealTor import selogerSpider
from scrapy.crawler import CrawlerProcess
from scrapy.settings import Settings


class MyListener(stomp.ConnectionListener):
def on_error(self, headers, message):
    print('received an error "%s"' % message)
def on_message(self, headers, message):
    print('received a message "%s"' % message)

    settings = Settings()
    settings.set("USER_AGENT",
                 "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) 
    AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.134 Safari/537.36")
    settings.set("LOG_ENABLED", False)
    crawler = CrawlerProcess(settings)
    crawler.crawl(selogerSpider)
    selogerSpider.signals.engine_started()
    print("STARTING scraping")
    crawler.start()
    print("Scraping STOPPED")
try:
conn = stomp.Connection()
conn.set_listener('', MyListener())
conn.start()
""" conn = stomp.Connection([('0.0.0.0', 61613)])"""
conn.connect('admin', 'password', wait=True)
conn.subscribe(destination='/queue/test', id=1, ack='auto')
print('subscripe')
"""conn.send(body=' '.join(sys.argv[1:]), destination='/queue/test')"""
input("coucou")
"""conn.disconnect()"""
print('end')

except IOError as e:
  print("error message")

Answer 1

这个问题与ActiveMQ没有任何关系。你滥用信号。作为Python documentation状态:

Python signal handlers are always executed in the main Python thread, even if the signal was received in another thread. This means that signals can’t be used as a means of inter-thread communication. You can use the synchronization primitives from the threading module instead.

Besides, only the main thread is allowed to set a new signal handler.

我相信 on_message 方法是在自己的线程中执行的，因为消息是异步接收的。

简而言之，不要使用来自线程的信号。使用 threading module 中的同步原语反而。如果您无法避免使用信号，则在主线程上同步接收 STOMP 消息，而不是使用 ConnectionListener。