一种改进的分布式实时事务调度协议

An Improved Distributed Real-time Transaction Scheduling Protocol

分布式实时事务调度协议用于实现事务间读写的并发控制,以满足事务的一致性与隔离性要求.本文改进了动态调整时间间隔的乐观并发控制协议,提出了一种分布式实时事务调度协议DOCC-DATI,协议分为读阶段、等待阶段、准备阶段和提交阶段.协议在读阶段和等待阶段利用事务的优先级信息,动态调整事务的串行化顺序,使高优先级事务优先进入验证阶段,并通过阻塞机制避免部分低优先级事务的不必要重启.由于分布式环境下处于准备阶段的数据不可访问,这将增加事务的阻塞时间,因此本文允许处于准备阶段的事务借出数据给低优先事务.为避免传统的两阶段提交协议中由单点故障而导致的实时事务阻塞,本文通过Paxos一致性算法提交分布式实时事务.提议的方法在一个模拟的分布式实时数据库环境中得以应用,显示出了优良的结果.

Distributed real-time transaction scheduling protocol which used to isolate the interference of concurrent transactions,is needed to achieve consistency and isolability requirements of transaction.On the base of optimistic concurrency control protocol w hich employ timestamp interval to dynamically adjust serialization order betw een transactions,an improved distributed real-time transaction scheduling protocol w hich is divided into reading phase,w aiting phase,preparing phase and commit phase is proposed.In reading phase and w aiting phase,the serialization order of transactions is dynamically adjusted based on their priorities.High priority transaction is allow ed to enter validation phase earlier and the unnecessary restart of transactions is avoided by blocking low-priority transactions.Prepared data w ould be inaccessible for a long time in distributed environment w hich w ould block transaction,so transaction in preparing phase is allow ed to lend data to low-priority transaction.In order to avoid blocking because of single failure,paxos commit protocol is employed for distributed real-time transaction commit.The proposed method has show n an excellent result in one simulated environment.