服务器长时间轮询并开始子处理每个呼叫的RFID卡号。如果时间太长，我的服务器就会崩溃。我怎么才能做得更好？

Question

我需要从RFID读卡器那里得到RFID卡号。这是客户端发起的。客户端AJAX发布到"/user/rfid“路由。这条路线要么返回“错误.”或者是rfid卡号。服务器打开检索此编号的子进程。如果服务器停留一段时间，用户尝试使用RFID登录，服务器就会中断。我需要一个更好的方法来完成这个任务，或者至少清除子进程？

有什么建议吗？

烧瓶路线

@app.route("/user/rfid", methods=["POST"])
def user_rfid():
    rfid = subprocess.Popen(["python", "rfidSimple.py"], stdout=subprocess.PIPE).stdout.read()
    print("rfid read: %s" % rfid)
    if(rfid == "Exiting...."):
        return json.dumps({"error":"rfid reader failure"})
    else:
        user = db.getUserByRFID(rfid.replace(" ",""))
        if("id" in user.keys()):
            # if credentials match, add user to session
            session["id"]       = user["id"]
            # return redirect url
            return json.dumps({"url":url_for("kiosk")})
        else:
            return json.dumps({"error":"rfid reader failure"})

rfidSimple.py

#!/usr/bin/env python

#Basic imports
from ctypes import *
import sys
#Phidget specific imports
from Phidgets.PhidgetException import PhidgetErrorCodes, PhidgetException
from Phidgets.Events.Events import AttachEventArgs, DetachEventArgs, ErrorEventArgs, OutputChangeEventArgs, TagEventArgs
from Phidgets.Devices.RFID import RFID, RFIDTagProtocol

# Rudimentary wait system variable
x = True
def rfidTagGained(e):
    global x
    source = e.device
    sys.stdout.write(e.tag)
    x = False

def main():
     #Create an RFID object
    try:
        rfid = RFID()
    except RuntimeError as e:
        sys.stdout.write("Exiting...")
    try:
        rfid.setOnTagHandler(rfidTagGained)
    except PhidgetException as e:
        sys.stdout.write("Exiting...")
    try:
        rfid.openPhidget()
    except PhidgetException as e:
        sys.stdout.write("Exiting...")

    try:
        rfid.waitForAttach(10000)
    except PhidgetException as e:
        # print("Phidget Exception %i: %s" % (e.code, e.details))
        try:
            rfid.closePhidget()
        except PhidgetException as e:
            sys.stdout.write("Exiting...")
    rfid.setAntennaOn(True)
    while x:
        # wait wait wait!
        pass
    exit(1)

if __name__ == '__main__':
    main()

Answer 1

您可以启动一个单独的线程来读取进程规范。在线程上执行连接(超时)，如果线程没有终止，您知道调用花费的时间太长，可以终止它。下面是一个示例，其中所有的内容都封装在一个类中。我没有测试它，它可能有错误，但您可能会发现这个想法很有用。

import threading
import subprocess
import time

class RfidSimple(threading.Thread):

    def __init__(self, timeout=10):
        super(theading.Thread, self).__init__()
        self.end = time.time() + timeout
        self.proc = subprocess.Popen(["python", "rfidSimple.py"],
            stdout=subprocess.PIPE)
        self.start()

    def run(self):
        self._result = self.proc.stdout.read()

    @property
    def result(self):
        timeout = self.end - time.time()
        if timeout > 0:
            self.join(timeout)
            if not self.isAlive():
                self.proc.wait()
                return self._result
        self.proc.terminate()
        self.join(5)
        if not self.isAlive():
            self.proc.wait()
            return "Exiting..."
        raise Exception("could not kill subprocess")

def user_rfid():
    rfid = RfidSimple().result
    print("rfid read: %s" % rfid)
    if(rfid == "Exiting...."):
        return json.dumps({"error":"rfid reader failure"})
    else:
        user = db.getUserByRFID(rfid.replace(" ",""))
        if("id" in user.keys()):
            # if credentials match, add user to session
            session["id"]       = user["id"]
            # return redirect url
            return json.dumps({"url":url_for("kiosk")})
        else:
            return json.dumps({"error":"rfid reader failure"})