Question

我有一个多线程代码 - 3个线程，它们轮询来自SQS的数据并将其添加到python队列中。 5个线程从python队列中获取消息，处理它们并将其发送到后端系统。

以下是代码：

python_queue = Queue.Queue()

class GetDataFromSQS(threading.Thread):
    """Threaded Url Grab"""
    def __init__(self, python_queue):
        threading.Thread.__init__(self)
        self.python_queue = python_queue

    def run(self):
        while True:
            time.sleep(0.5) //sleep for a few secs before querying again
            try:
                msgs = sqs_queue.get_messages(10)
                if msgs == None:
                    print "sqs is empty now"!
                for msg in msgs:
                    #place each message block from sqs into python queue for processing
                    self.python_queue.put(msg)
                    print "Adding a new message to Queue. Queue size is now %d" % self.python_queue.qsize()
                    #delete from sqs
                    sqs_queue.delete_message(msg)
            except Exception as e:
                print "Exception in GetDataFromSQS :: " +  e


class ProcessSQSMsgs(threading.Thread):
    def __init__(self, python_queue):
        threading.Thread.__init__(self)
        self.python_queue = python_queue
        self.pool_manager = PoolManager(num_pools=6)

    def run(self):
        while True:
            #grabs the message to be parsed from sqs queue
            python_queue_msg = self.python_queue.get()
            try:
                processMsgAndSendToBackend(python_queue_msg, self.pool_manager)
            except Exception as e:
                print "Error parsing:: " + e
            finally:
                self.python_queue.task_done()

def processMsgAndSendToBackend(msg, pool_manager):
    if msg != "":
        ###### All the code related to processing the msg
        for individualValue in processedMsg:
            try:
                response = pool_manager.urlopen('POST', backend_endpoint, body=individualValue)
                if response == None:
                    print "Error"
                else:
                    response.release_conn()
            except Exception as e:
                print "Exception! Post data to backend: " + e


def startMyPython():
    #spawn a pool of threads, and pass them queue instance
    for i in range(3):
        sqsThread = GetDataFromSQS(python_queue)
        sqsThread.start()

    for j in range(5):
        parseThread = ProcessSQSMsgs(python_queue)
        #parseThread.setDaemon(True)
        parseThread.start()

    #wait on the queue until everything has been processed
    python_queue.join()
    # python_queue.close() -- should i do this?

startMyPython()

问题： 3个python worker每隔几天随机死亡（使用top -p -H监视），如果我终止进程并再次启动脚本，一切都会正常。我怀疑那些消失的工作者是3个GetDataFromSQS线程。而且因为GetDataFromSQS死了，其他5个工作者虽然在运行时总是睡觉，因为python队列中没有数据。我不知道我在这里做错了什么因为我对python很新，并且按照本教程创建了这个排队逻辑和线程 - http://www.ibm.com/developerworks/aix/library/au-threadingpython/

提前感谢您的帮助。希望我已经清楚地解释了我的问题。

Answer 1

线程挂起的问题与获取sqs队列的句柄有关。我使用IAM来管理凭证，使用boto sdk连接到sqs。

此问题的根本原因是boto包正在从AWS读取auth的元数据，并且偶尔会失败。

修复方法是编辑boto配置，增加对AWS执行auth调用的尝试。

[宝途] metadata_service_num_attempts = 5

（https://groups.google.com/forum/#!topic/boto-users/1yX24WG3g1E）

线程轮询sqs并将其添加到python队列以处理die

1 个答案: