Fairly Decentralizing a Hybrid Concurrency Control Protocol for Real-Time Database Systems

Abstract

Concurrency control protocols play a vital role in ensuring the correctness of databases when transactions are processed in parallel. Plor is a non-real-time concurrency control protocol based on the 2-phase locking protocol. Plor utilizes the Wound-Wait scheme, a timestamp-based scheme for deadlock prevention, as it provides lower tail latency. One problem of Plor with that it requires transactions to fetch timestamps from a single centralized atomic counter. This paper evaluates the implementation of the Fair Thread ID method (FairTID), a decentralized approach where transactions use the thread IDs as their timestamps instead. The FairTID method shows up to 1.5 times throughput improvement while reducing latency by 1.6 times and the deadline-miss ratio by 1.67 times over the baseline protocol. The application of the method is formally verified for fairness reasoning.