Question

我需要运行一次处理最多3个请求的服务器。我的设计是运行TCP服务器并运行3个线程来处理这些请求。服务器将接受请求，并将使用相应的锁定队列将这些请求传递给线程。我也有适当的队列锁。我的问题是，即使我有一个信号处理程序，在主进程必须退出时使用标志来通知线程。我不明白错误是什么，因为优雅的退出没有按预期发生。输出如下：

vm:~/Desktop$ python multi_threaded_queueing.py
About to kickoff
About to kickoff
Starting Thread-1
About to kickoff
Starting Thread-2
Starting Thread-3
^CTraceback (most recent call last):
  File "multi_threaded_queueing.py", line 94, in <module>
    conn, addr = s.accept()
  File "/usr/lib/python2.7/socket.py", line 202, in accept
    sock, addr = self._sock.accept()
socket.error: [Errno 4] Interrupted system call

代码如下：

#!/usr/bin/python

import Queue
import threading
import time
import sys
import socket
import signal


HOST = '127.0.0.1'
PORT = 50007              # Arbitrary non-privileged port
s = None

exitFlag = 0
#signal handler for control C
def signal_handler(signal, frame):
    print "Control+C has been pressed"
    #setting the exit flag so that all the threads can get notified
    exitFlag = 1
    #wait till all the threads have finished processing and can gracefully exit
    #I maintain an array for each thread to set the corresponding index when
    #it has finished its processing. I and all the elements to see if its 0
    #and based on which I will exit or wait
    while 1:
        num = 0
        for ele in exitList:
            num &= ele
        if ele == 0:
            sys.exit(0)

class myThread (threading.Thread):
    #have a queue, thread ID and name for every thread.
    def __init__(self, threadID, name, q):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.q = q
    def run(self):
        print "Starting " + self.name
        process_data(self.name, self.q, self.threadID)
        print "Exiting " + self.name

def process_data(threadName, q, threadID):
    #while exit flag is not set by the main thread keep processing the data
    #present in the queue.
    while not exitFlag:
        queueLock[threadID].acquire()
        if not workQueue[threadID].empty():
            data = q[threadID].get()
            queueLock[threadID].release()
            print "%s processing %s" % (threadName, data)
        else:
            queueLock[threadID].release()
        time.sleep(1)
    exitThread[threadID] = 1

threadList = ["Thread-1", "Thread-2", "Thread-3"]
nameList = ["One", "Two", "Three", "Four", "Five"]
queueLock = []
workQueue = []
threads = []
threadID = 0
exitList = []
size = 3
request = 0
signal.signal(signal.SIGINT, signal_handler)

# Create new threads
#by default hard coding the number of threads to 3
for tName in threadList:
    workQueue.append(Queue.Queue(10))
    queueLock.append(threading.Lock())
    exitList.append(0)
    thread = myThread(threadID, tName, workQueue)
    print "About to kickoff"
    thread.start()
    threads.append(thread)
    threadID += 1


for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
    af, socktype, proto, canonname, sa = res
    try:
        socket.setdefaulttimeout(10)
        s = socket.socket(af, socktype, proto)
    except socket.error, msg:
        s = None
        continue
    try:
        s.bind(sa)
        s.listen(1)
    except socket.error, msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print 'could not open socket'
    sys.exit(1)
while 1:
    conn, addr = s.accept()
    print 'Connected by', addr
    request += 1
    #round robin scheduling for each thread
    thread_index = request % size
    while 1:
        data = conn.recv(1024)
        if not data: break
        # Fill the queue with the request received
        queueLock[thread_index].acquire()
        for word in nameList:
            workQueue[thread_index].put(word)
        queueLock[thread_index].release()
        # Wait for queue to empty
        while not workQueue[thread_index].empty():
            pass
        conn.send(data)
    conn.close()



# Notify threads it's time to exit
exitFlag = 1
print "setting the exitFlag"
# Wait for all threads to complete
for t in threads:
    t.join()
print "Exiting Main Thread"

Answer 1

还有很多事情要发生。

signal_handler(signal, frame):未设置全局exitFlag。您需要将global exitFlag添加到函数顶部。
sys.exit()并未真正退出 - 只会引发KeyboardInterrupt错误。
socket.error: [Errno 4] Interrupted system call是好东西，它可以阻止你的程序陷入conn, addr = s.accept()。您应该捕获socket.error个例外并使用它们来突破while循环。

TCP线程python服务器不按预期处理信号

1 个答案: