这个python代码线程是否安全(带扭曲的线程)？

Question

我正在编写一个应用程序来收集UDP消息并每1秒处理一次.

应用程序原型如下:

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor
import threading
import time

class UdpListener(DatagramProtocol):

    messages = []

    def datagramReceived(self, data, (host, port)):
        self.messages.append(data)

class Messenger(threading.Thread):

    listener = None

    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        while True:
            time.sleep(1)
            recivedMessages = self.listener.messages
            length = len(recivedMessages)
            messagesToProccess = recivedMessages[0:length]
            #doSomethingWithMessages(messagesToProccess)
            del self.listener.messages[0:length]
            print(length)

listener = UdpListener()

messenger = Messenger()
messenger.listener = listener
messenger.start()

reactor.listenUDP(5556, listener)
reactor.run()

我不确定我是否可以轻松地从列表中删除起始值(del self.listener.messages [0:length]),而不会有任何传入消息更改列表和应用程序崩溃的风险.

更新 - 带锁的版本

class Messenger(threading.Thread):

listener = None
lock = threading.Lock()

def __init__(self):
    threading.Thread.__init__(self)

def run(self):
    while True:
        time.sleep(1)
        recivedMessages = self.listener.messages
        self.lock.acquire()
        try:
            length = len(recivedMessages)
            messagesToProccess = recivedMessages[0:length]
            del self.listener.messages[0:length]
        except Exception as e:
            raise e
        finally:
            self.lock.release()

        #doSomethingWithMessages(messagesToProccess)
        print(length)

Answer 1

您的代码不是线程安全的,不是.你需要锁定messages.

但是,这里不需要线程.为什么不这样做？

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor

class UdpListener(DatagramProtocol):
    callingLater = False

    messages = []

    def process(self):
        doSomethingWithMessages(self.messages)
        self.messages = []
        self.callingLater = False

    def datagramReceived(self, data, (host, port)):
        self.messages.append(data)
        if not self.callingLater:
            reactor.callLater(1.0, self.process)
            self.callingLater = True

listener = UdpListener()

reactor.listenUDP(5556, listener)
reactor.run()

更新:以下是原始版本如何使用锁定,仅用于教育目的.请注意,这不是那么有效,也更容易出错.编辑:将所有消息逻辑分离出来,UdpListener以便使用它的类不需要知道其粘滞的内部细节.

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor
import threading
import time

class UdpListener(DatagramProtocol):
    message_lock = threading.Lock()
    messages = []

    def datagramReceived(self, data, (host, port)):
        with self.message_lock:
            self.messages.append(data)

    def getAndClearMessages(self):
        with self.message_lock:
            res = self.messages
            self.messages = []
        return res

class Messenger(threading.Thread):

    listener = None

    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        while True:
            time.sleep(1)
            recivedMessages = self.listener.getAndClearMessages()
            length = len(recivedMessages)
            #doSomethingWithMessages(recivedMessages)
            print(length)

listener = UdpListener()

messenger = Messenger()
messenger.listener = listener
messenger.start()

reactor.listenUDP(5556, listener)
reactor.run()