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backends/kylin-assistant-daemon/src/single.py

 

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#!/usr/bin/python3

 

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# -*- coding: utf-8 -*-

 

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import os, sys, shutil, tempfile

 

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import subprocess

 

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# ensure that single instance of applet is running for each user

 

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class SingleInstance(object):

 

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    #Initialize, specifying a path to store pids

 

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    def __init__(self,pidPath):

 

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        self.pidPath = pidPath

 

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        self.lasterror = False

 

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        if os.path.exists(pidPath):

 

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            # Make sure it is not a "stale" pidFile

 

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            pid = open(pidPath, 'r').read().strip()

 

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            # Check list of running pids, if not running it is stale so overwrite

 

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            pidRunning = subprocess.getoutput('ls -1 /proc | grep ^%s$' % pid)

 

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            self.lasterror = True if pidRunning else False

 

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        else:

 

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            self.lasterror = False

 

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        if not self.lasterror:

 

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            # Create a temp file, copy it to pidPath and remove temporary file

 

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            (fp, temp_path) = tempfile.mkstemp()

 

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            try:

 

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                os.fdopen(fp, "w+b").write(bytes(os.getpid()))

 

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                shutil.copy(temp_path, pidPath)

 

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                os.unlink(temp_path)

 

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            except Exception as e:

 

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                print(str(e))

 

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    def is_already_running(self):

 

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         return self.lasterror

 

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    def __del__(self):

 

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         if not self.lasterror and os.path.exists(self.pidPath):

 

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            os.unlink(self.pidPath)

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