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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017-2018 Wind River Systems, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
import time
import redis
from django.conf import settings
class SharedLock:
def __init__(self, lock_key, host=settings.REDIS_HOST,
port=settings.REDIS_PORT,
password=settings.REDIS_PASSWD, db=9, lock_timeout=5 * 60):
self.lock_key = lock_key
self.lock_timeout = lock_timeout
self.redis = redis.Redis(host=host, port=port, db=db, password=password)
self.acquire_time = -1
def acquire(self):
begin = now = int(time.time())
while (now - begin) < self.lock_timeout:
result = self.redis.setnx(self.lock_key, now + self.lock_timeout + 1)
if result == 1 or result is True:
self.acquire_time = now
return True
current_lock_timestamp = self.redis.get(self.lock_key)
if not current_lock_timestamp:
time.sleep(1)
continue
current_lock_timestamp = int(current_lock_timestamp)
if now > current_lock_timestamp:
next_lock_timestamp = self.redis.getset(self.lock_key, now + self.lock_timeout + 1)
if not next_lock_timestamp:
time.sleep(1)
continue
next_lock_timestamp = int(next_lock_timestamp)
if next_lock_timestamp == current_lock_timestamp:
self.acquire_time = now
return True
else:
time.sleep(1)
continue
return False
def release(self):
now = int(time.time())
if now > self.acquire_time + self.lock_timeout:
# key expired, do nothing and let other clients handle it
return
self.acquire_time = None
self.redis.delete(self.lock_key)
def do_biz_with_share_lock(lock_name, callback):
lock = SharedLock(lock_name)
try:
if not lock.acquire():
raise Exception(lock_name + " timeout")
callback()
except Exception as e:
raise e
finally:
lock.release()
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