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# -*- coding: utf-8 -*-
"""
This is an abstract class providing common methods shared by all service types.
The semantics of the lock file mechanism may be found `here <https://github.com/subuser-security/subuser/issues/31>`_ .
"""
#external imports
import abc
import json
import os
import errno
import fcntl
import shutil
import sys
from collections import OrderedDict
#internal imports
from subuserlib.classes.userOwnedObject import UserOwnedObject
class Service(UserOwnedObject):
__metaclass__ = abc.ABCMeta
def __init__(self,user,subuser):
self.__subuser = subuser
UserOwnedObject.__init__(self,user)
@abc.abstractmethod
def start(self,serviceStatus):
"""
Start the service. Block untill the service has started. Returns a modified service status dictionary with any service specific properties set.
"""
pass
@abc.abstractmethod
def stop(self,serviceStatus):
"""
Stop the service. Block untill the service has stopped.
"""
pass
@abc.abstractmethod
def cleanUp(self):
pass
@abc.abstractmethod
def isRunning(self,serviceStatus):
"""
Returns True if the services is running.
"""
pass
def getLockfileDir(self):
return os.path.join(self.user.config["lock-dir"],"services",self.__subuser.name)
def getLockfilePath(self):
return os.path.join(self.getLockfileDir(),self.name+".json")
def removeLockFile(self):
os.remove(self.getLockfilePath())
try:
os.rmdir(self.getLockfileDir())
except OSError:
pass
def getLock(self):
try:
self.user.endUser.makedirs(self.getLockfileDir())
except OSError as exception:
if exception.errno != errno.EEXIST:
raise
while True:
try:
lockFd = open(self.getLockfilePath(),mode="r+")
break
except IOError:
self.user.endUser.create_file(self.getLockfilePath())
fcntl.flock(lockFd,fcntl.LOCK_EX)
return lockFd
def addClient(self):
"""
Increase the services client counter, starting the service if necessary. Blocks untill the service is ready to accept the new client.
"""
with self.getLock() as lockFile:
try:
serviceStatus = json.load(lockFile, object_pairs_hook=OrderedDict)
except ValueError:
serviceStatus = {}
serviceStatus["client-counter"] = 0
if serviceStatus["client-counter"] == 0 or not self.isRunning(serviceStatus):
serviceStatus["client-counter"] = 0
serviceStatus = self.start(serviceStatus)
serviceStatus["client-counter"] = serviceStatus["client-counter"] + 1
lockFile.seek(0)
lockFile.truncate()
json.dump(serviceStatus,lockFile)
fcntl.flock(lockFile,fcntl.LOCK_UN)
def removeClient(self):
"""
Decrease the services client counter, stopping the service if no longer necessary.
"""
noMoreClients = False
with self.getLock() as lockFile:
try:
lock_info = lockFile.read()
serviceStatus = json.loads(lock_info, object_pairs_hook=OrderedDict)
except ValueError as e:
sys.exit("Error in lock file. Failed to release lock:\n"+lock_info+"\n"+str(e))
serviceStatus["client-counter"] = serviceStatus["client-counter"] - 1
if serviceStatus["client-counter"] < 0:
raise RemoveClientException("The client-counter is already zero. Client cannot be removed! \n" + str(serviceStatus))
if serviceStatus["client-counter"] == 0:
self.stop(serviceStatus)
noMoreClients = True
lockFile.seek(0)
lockFile.truncate()
json.dump(serviceStatus,lockFile)
if noMoreClients:
self.removeLockFile()
fcntl.flock(lockFile,fcntl.LOCK_UN)
def cleanUpIfNotRunning(self):
"""
Check if running.
If not running, run cleanUp method.
"""
with self.getLock() as lockFile:
try:
serviceStatus = json.load(lockFile, object_pairs_hook=OrderedDict)
except ValueError:
serviceStatus = {}
serviceStatus["client-counter"] = 0
if serviceStatus["client-counter"] == 0 or not self.isRunning(serviceStatus):
self.cleanUp()
self.removeLockFile()
fcntl.flock(lockFile,fcntl.LOCK_UN)
class RemoveClientException(Exception):
pass
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