python库介绍-python-daemon: 实现python后台程序

简介

python-daemon实现Unix守护进程。 参考：PEP 3143

该库实现了PEP 3143“标准守护进程库”的良好行为守护进程规范。

DaemonContext实例保存程序的行为和配置的进程环境。

快速入门

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import time

with daemon.DaemonContext():
    f = open("/tmp/test.log",'w')
    while True:
        f.write('''
        Library to implement a well-behaved Unix daemon process.

This library implements the well-behaved daemon specification of PEP 3143, “Standard daemon process library”.

A well-behaved Unix daemon process is tricky to get right, but the required steps are much the same for every daemon program. A DaemonContext instance holds the behaviour and configured process environment for the program; use the instance as a context manager to enter a daemon state.
''')
        f.write("{0}\n".format(time.ctime(time.time())))
        time.sleep(1)

执行：

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$ python3 daemon1.py 

$ tail -f /tmp/test.log 
This library implements the well-behaved daemon specification of PEP 3143, “Standard daemon process library”.

A well-behaved Unix daemon process is tricky to get right, but the required steps are much the same for every daemon program. A DaemonContext instance holds the behaviour and configured process environment for the program; use the instance as a context manager to enter a daemon state.
Thu Feb  8 14:21:43 2018

$ ps afx | grep -i daemon1
 8646 pts/2    S+     0:00          |           \_ grep --color=auto -i daemon1
 8640 ?        S      0:00          \_ python3 daemon1.py
$ kill -9 8640

要想停止上述进程，可以通过ps查找到进程号，然后kill。

注意上述代码在python2没有任何问题，不过在python需要修改库文件runner.py打开文件的方式。

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# vi /usr/local/lib/python3.5/dist-packages/daemon/runner.py 
# 118 -120
        self.daemon_context = DaemonContext()
        self.daemon_context.stdin = open(app.stdin_path, 'wb+',buffering=0)
        self.daemon_context.stdout = open(app.stdout_path,  'wb+',buffering=0)
        self.daemon_context.stderr = open(
                app.stderr_path, 'wb+', buffering=0)

更实用的例子

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import time
import logging
import logging.handlers
from daemon import runner

class App():

    def __init__(self):
        self.stdin_path = '/dev/null'
        self.stdout_path = '/dev/tty'
        self.stderr_path = '/dev/tty'
        self.pidfile_path =  '/tmp/foo.pid'
        self.pidfile_timeout = 5

    def run(self):

        logs = logging.getLogger('MyLogger')
        logs.setLevel(logging.DEBUG)
        fh = logging.handlers.RotatingFileHandler(
            '/tmp/test.log',maxBytes=10000000,backupCount=5)
        fh.setLevel(logging.DEBUG)
        formatter = logging.Formatter(u'%(asctime)s [%(levelname)s] %(message)s')
        fh.setFormatter(formatter)
        logs.addHandler(fh)  

        while True:
            for i in range(10):
                logs.info("Beginning Scan {0}! \n".format(i))
            time.sleep(1)

app = App()
daemon_runner = runner.DaemonRunner(app)
daemon_runner.do_action()

执行：

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$ python2 daemon2.py 
usage: daemon2.py start|stop|restart

$ python3 daemon2.py  start
andrew@andrew-MS-7A71:~/code/python-chinese-library/libraries/daemon$ 
andrew@andrew-MS-7A71:~/code/python-chinese-library/libraries/daemon$ Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/lockfile/pidlockfile.py", line 77, in acquire
    write_pid_to_pidfile(self.path)
  File "/usr/local/lib/python3.5/dist-packages/lockfile/pidlockfile.py", line 161, in write_pid_to_pidfile
    pidfile_fd = os.open(pidfile_path, open_flags, open_mode)
FileExistsError: [Errno 17] File exists: '/tmp/foo.pid'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "daemon2.py", line 39, in <module>
    daemon_runner.do_action()
  File "/usr/local/lib/python3.5/dist-packages/daemon/runner.py", line 274, in do_action
    func(self)
  File "/usr/local/lib/python3.5/dist-packages/daemon/runner.py", line 182, in _start
    self.daemon_context.open()
  File "/usr/local/lib/python3.5/dist-packages/daemon/daemon.py", line 389, in open
    self.pidfile.__enter__()
  File "/usr/local/lib/python3.5/dist-packages/lockfile/__init__.py", line 197, in __enter__
    self.acquire()
  File "/usr/local/lib/python3.5/dist-packages/daemon/pidfile.py", line 60, in acquire
    super(TimeoutPIDLockFile, self).acquire(timeout, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/lockfile/pidlockfile.py", line 85, in acquire
    self.path)
lockfile.LockTimeout: Timeout waiting to acquire lock for /tmp/foo.pid

andrew@andrew-MS-7A71:~/code/python-chinese-library/libraries/daemon$ python3 daemon2.py  stop
Terminating on signal 15
andrew@andrew-MS-7A71:~/code/python-chinese-library/libraries/daemon$ python3 daemon2.py  stop
Traceback (most recent call last):
  File "daemon2.py", line 39, in <module>
    daemon_runner.do_action()
  File "/usr/local/lib/python3.5/dist-packages/daemon/runner.py", line 274, in do_action
    func(self)
  File "/usr/local/lib/python3.5/dist-packages/daemon/runner.py", line 224, in _stop
    raise error
daemon.runner.DaemonRunnerStopFailureError: PID file '/tmp/foo.pid' not locked

注意上面的错误是重复启动或者停止时进程并不存在导致的。

参考资料

本文代码地址： http://t.cn/R8scWAe

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daemonize demo无法运行

https://pypi.python.org/pypi/python-daemon

老式书写后台进程的一种方式

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import time
import logging
import logging.handlers


logs = logging.getLogger('MyLogger')
logs.setLevel(logging.DEBUG)
fh = logging.handlers.RotatingFileHandler(
    '/tmp/test.log',maxBytes=10000000,backupCount=5)
fh.setLevel(logging.DEBUG)
formatter = logging.Formatter(u'%(asctime)s [%(levelname)s] %(message)s')
fh.setFormatter(formatter)
logs.addHandler(fh)  


while True:
    for i in range(10):
        logs.info("Beginning Scan {0}! \n".format(i))
    time.sleep(1)

这样并不能后台执行，但是可以借助linux的nohup和&。为此添加如下的启动和停止脚本，其实也不麻烦：

shell脚本参见： http://t.cn/R8scWAe

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$ sh startup.sh 
================================================================================================================
Starting older.py(PID=15315)...[Success]
================================================================================================================
$ sh startup.sh 
================================================================================================================
older.py already started(PID=15315)
================================================================================================================
$ sh shutdown.sh 
================================================================================================================
Stopping older.py(PID=15315)...[Success]
================================================================================================================
$ sh shutdown.sh 
================================================================================================================
older.py is not running
================================================================================================================

其他

supervisord 可以linux控制linux进程，当然也可以后台化。

How do you create a daemon in Python?

另外也可以向linux systemd注册为后台进程。

links