python守护进程信号不起作用

Question

I wrote a python daemon script and registered some signal handlers , but when i use kill -1 pid , i found that signal handler does not work.

Any body know why?

Here is the script:

test.py:

#!/usr/bin/env python

import sys, time
from daemon import Daemon
import threading
import signal

class MyDaemon(Daemon):
    def run(self):
        time.sleep(1)
        threading.Thread(target=mythread).start()
        threading.Thread(target=mythread2).start()


def mythread():
    while 1:
        raise Exception,"shit"

def mythread2():
    while 1:
        time.sleep(1)
        print "22222222222"



if __name__ == "__main__":
    daemon = MyDaemon('/tmp/daemon-example.pid')
    if len(sys.argv) == 2:
        if 'start' == sys.argv[1]:
            daemon.start()
        elif 'stop' == sys.argv[1]:
            daemon.stop()
        elif 'restart' == sys.argv[1]:
            daemon.restart()
        else:
            print "Unknown command"
            sys.exit(2)
        sys.exit(0)
    else:
        print "usage: %s start|stop|restart" % sys.argv[0]
        sys.exit(2)

daemon.py:

#!/usr/bin/env python

import sys, os, time, atexit
from signal import SIGTERM 
import signal
import logging
import logging.handlers

LOG_FILENAME = "/tmp/myservice.log"
LOG_LEVEL = logging.INFO  # Could be e.g. "DEBUG" or "WARNING"

# Configure logging to log to a file, making a new file at midnight and keeping the last 3 day's data
# Give the logger a unique name (good practice)
logger = logging.getLogger(__name__)
# Set the log level to LOG_LEVEL
logger.setLevel(LOG_LEVEL)
# Make a handler that writes to a file, making a new file at midnight and keeping 3 backups
handler = logging.handlers.TimedRotatingFileHandler(LOG_FILENAME, when="midnight", backupCount=3)
# Format each log message like this
formatter = logging.Formatter('%(asctime)s %(levelname)-8s %(message)s')
# Attach the formatter to the handler
handler.setFormatter(formatter)
# Attach the handler to the logger
logger.addHandler(handler)

# Make a class we can use to capture stdout and sterr in the log
class MyLogger(object):
    def __init__(self, logger, level):
            """Needs a logger and a logger level."""
            self.logger = logger
            self.level = level

    def write(self, message):
            # Only log if there is a message (not just a new line)
            if message.rstrip() != "":
                    self.logger.log(self.level, message.rstrip())

# Replace stdout with logging to file at INFO level
sys.stdout = MyLogger(logger, logging.INFO)
# Replace stderr with logging to file at ERROR level
sys.stderr = MyLogger(logger, logging.ERROR)


def signal_handler(signum,stack):
    print "signal:%s" % signum


signal.signal(signal.SIGHUP,signal_handler)
signal.signal(signal.SIGINT,signal_handler) 
signal.signal(signal.SIGTERM,signal_handler)


class Daemon:
    """
    A generic daemon class.

    Usage: subclass the Daemon class and override the run() method
    """
    def __init__(self, pidfile, stdin='/dev/null', stdout='/tmp/out.txt', stderr='/tmp/err.txt'):
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr
        self.pidfile = pidfile

    def daemonize(self):
        """
        do the UNIX double-fork magic, see Stevens' "Advanced 
        Programming in the UNIX Environment" for details (ISBN 0201563177)
        http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
        """
        try: 
            pid = os.fork() 
            if pid > 0:
                # exit first parent
                sys.exit(0) 
        except OSError, e: 
            sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1)

        # decouple from parent environment
        os.chdir("/") 
        os.setsid() 
        os.umask(0) 

        # do second fork
        try: 
            pid = os.fork() 
            if pid > 0:
                # exit from second parent
                sys.exit(0) 
        except OSError, e: 
            sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
            sys.exit(1) 

        # redirect standard file descriptors
        # sys.stdout.flush()
        # sys.stderr.flush()
        # si = file(self.stdin, 'r')
        # so = file(self.stdout, 'a+', 0)
        # se = file(self.stderr, 'a+', 0)
        # os.dup2(si.fileno(), sys.stdin.fileno())
        # os.dup2(so.fileno(), sys.stdout.fileno())
        # os.dup2(se.fileno(), sys.stderr.fileno())



        # write pidfile
        atexit.register(self.delpid)
        pid = str(os.getpid())
        file(self.pidfile,'w+').write("%s\n" % pid)

    def delpid(self):
        os.remove(self.pidfile)


    def start(self):
        """
        Start the daemon
        """
        # Check for a pidfile to see if the daemon already runs
        try:
            pf = file(self.pidfile,'r')
            pid = int(pf.read().strip())
            pf.close()
        except IOError:
            pid = None

        if pid:
            message = "pidfile %s already exist. Daemon already running?\n"
            sys.stderr.write(message % self.pidfile)
            sys.exit(1)

        # Start the daemon
        self.daemonize()
        self.run()

    def stop(self):
        """
        Stop the daemon
        """
        # Get the pid from the pidfile
        try:
            pf = file(self.pidfile,'r')
            pid = int(pf.read().strip())
            pf.close()
        except IOError:
            pid = None

        if not pid:
            message = "pidfile %s does not exist. Daemon not running?\n"
            sys.stderr.write(message % self.pidfile)
            return # not an error in a restart

        # Try killing the daemon process    
        try:
            while 1:
                os.kill(pid, SIGTERM)
                time.sleep(0.1)
        except OSError, err:
            err = str(err)
            if err.find("No such process") > 0:
                if os.path.exists(self.pidfile):
                    os.remove(self.pidfile)
            else:
                print str(err)
                sys.exit(1)

    def restart(self):
        """
        Restart the daemon
        """
        self.stop()
        self.start()

    def run(self):
        """
        You should override this method when you subclass Daemon. It will be called after the process has been
        daemonized by start() or restart().
        """

As you can see, when i use kill command to the test.py , there is nothing print in the log files.

Answer 1

Signals are only delivered to a single thread. If delivered to your first thread mythread() since it has stopped due to an exception, nothing will happen.

Try reversing the order of dispatch of threads to see.