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