无限运行服务器端 python 脚本？

Question

我想替换 Cron Jobs 以“保持”我的程序处于活动状态，因为无论脚本是否已被调用，它都会每隔 XX 间隔调用一次，从而创建重复的条目。

我调查了这个问题，并有一些方法。一种是修改我的程序，以便检查它是否已被调用并自行关闭。我追求的是通过使用execfile 一遍又一遍地调用自己来将它与 Cronjob 完全分离，这完全符合我的要求，除了以下问题： RuntimeError: maximum recursion depth exceeded

有没有办法让程序保持“无限循环”而不会出现堆栈溢出？

这是我的代码，它是一个检查邮件并将其转换为 MySQL 数据库条目的程序。

imap = imaplib.IMAP4(hst)

try:
   imap.login(usr, pwd)
except Exception as e:
   errormsg = e
   time.sleep(30)
   print "IMAP error: " + str(errormsg)
   execfile('/var/www/html/olotool/converter.py')
   raise IOError(e)


# Authentification & Fetch Step

while True:

    time.sleep(5)
    '''
    The script will always result in an error if there
    are no mails left to check in the inbox. It then
    goes into sleep mode and relaunches itself to check
    if new mails have arrived.
    '''
    try:
        imap.select("Inbox") # Tell Imap where to go
        result, data = imap.uid('search', None, "ALL")
        latest = data[0].split()[-1]
        result, data = imap.uid('fetch', latest, '(RFC822)')
        raw = data[0][1] # This contains the Mail Data
        msg = email.message_from_string(raw)

    except Exception as e:
        disconnect(imap)
        time.sleep(60)
        execfile('/var/www/html/olotool/converter.py')
        raise IOError(e)

Answer 1

我现在用我认为可能的唯一方法自己解决了这个问题。 首先我在上面的代码中改变了我的异常：

except Exception as e:
    disconnect(imap)
    print "Converter: No messages left"
    raise os._exit(0) 
    # This is a special case since this Exception is
    # no error thus os._exit(0) gives no false-positives

如您所见，我现在避免使用execfile。相反，我编写了一个控制器脚本来检查我的 converter.py 的状态并在它尚未运行时启动它：

while True:

    presL = os.popen('pgrep -lf python').read()
    print "________________________________________"
    print "Starting PIDcheck"
    print "Current Processes: " 
    print presL # Check Processes

    presRconverter = find('\d{7} python converter.py', presL)
    if presRconverter:
        # Store the PID
        convPID = find('\d{7}', presRconverter)
        print "Converter is running at PID: " + convPID

    else:
        print "PID Controller: Converter not running"
        try:
            print "PID Controller: Calling converter"
            subprocess.check_call('python converter.py', shell=True)

        except subprocess.CalledProcessError as e:
            errormsg = e
            print "Couldn't call Converter Module"
            sendMail(esender,ereceiver,esubject,etext,server)
            print "Error notification send"
            raise IOError(e)

    # If we got until here without ERROR, the call was Successfull
    print "PID Controller: Call successful"
    print "________________________________________"
    time.sleep(60)

此方法不会引发：RuntimeError: maximum recursion depth exceeded。如果您使用命令nohup python converter.py 运行控制器，这还会为您提供nohup.out 文件，您可以在其中看到错误处理的任何问题。

我希望我可以帮助遇到同样问题的人。

Answer 2

类似这样的东西应该可以工作，而不必求助于子进程检查等：

def check_mail_loop():
    imap = imaplib.IMAP4(hst)
    # Build some function to login, and, in the event of an error, sleep for n seconds and call login function again.
    imap.login(usr, pwd)

    while True:
        try:
            imap.select("Inbox")
            result, data = imap.uid('search', None, "ALL")

            if result and data:
                latest = data[0].split()[-1]
                result, data = imap.uid('fetch', latest, '(RFC822)')
                raw = data[0][1] # This contains the Mail Data
                msg = email.message_from_string(raw)
            time.sleep(5)
        except SomeRelevantException as e:
            logging.log(e)
            time.sleep(60)
            pass

如果出现您没有预见到的随机错误，请使用流程控制管理器，例如 supervisord 或 monit。