multivimbroker/multivimbroker/pub/utils/share_lock.py

   1 #!/usr/bin/env python
   2 # -*- coding: utf-8 -*-
   3 # Copyright (c) 2017 Wind River Systems, Inc.
   4 # Copyright (c) 2017-2018 VMware, Inc.
   5 #
   6 # Licensed under the Apache License, Version 2.0 (the "License");
   7 # you may not use this file except in compliance with the License.
   8 # You may obtain a copy of the License at:
   9 #       http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14
  15 import time
  16
  17 import redis
  18
  19 from multivimbroker.pub.config.config import REDIS_HOST
  20 from multivimbroker.pub.config.config import REDIS_PORT
  21 from multivimbroker.pub.config.config import REDIS_PASSWD
  22
  23
  24 class SharedLock:
  25     def __init__(self, lock_key, host=REDIS_HOST, port=REDIS_PORT,
  26                  password=REDIS_PASSWD, db=9, lock_timeout=5 * 60):
  27         self.lock_key = lock_key
  28         self.lock_timeout = lock_timeout
  29         self.redis = redis.Redis(host=host, port=port,
  30                                  db=db, password=password)
  31         self.acquire_time = -1
  32
  33     def acquire(self):
  34         begin = now = int(time.time())
  35         while (now - begin) < self.lock_timeout:
  36
  37             result = self.redis.setnx(self.lock_key, now +
  38                                       self.lock_timeout + 1)
  39             if result == 1 or result is True:
  40                 self.acquire_time = now
  41                 return True
  42
  43             current_lock_timestamp = self.redis.get(self.lock_key)
  44             if not current_lock_timestamp:
  45                 time.sleep(1)
  46                 continue
  47
  48             current_lock_timestamp = int(current_lock_timestamp)
  49
  50             if now > current_lock_timestamp:
  51                 next_lock_timestamp = self.redis.getset(self.lock_key, now +
  52                                                         self.lock_timeout + 1)
  53                 if not next_lock_timestamp:
  54                     time.sleep(1)
  55                     continue
  56                 next_lock_timestamp = int(next_lock_timestamp)
  57
  58                 if next_lock_timestamp == current_lock_timestamp:
  59                     self.acquire_time = now
  60                     return True
  61             else:
  62                 time.sleep(1)
  63                 continue
  64         return False
  65
  66     def release(self):
  67         now = int(time.time())
  68         if now > self.acquire_time + self.lock_timeout:
  69             # key expired, do nothing and let other clients handle it
  70             return
  71         self.acquire_time = None
  72         self.redis.delete(self.lock_key)
  73
  74
  75 def do_biz_with_share_lock(lock_name, callback):
  76     lock = SharedLock(lock_name)
  77     try:
  78         if not lock.acquire():
  79             raise Exception(lock_name + " timeout")
  80         callback()
  81     except Exception as e:
  82         raise e
  83     finally:
  84         lock.release()