Managing deadline miss ratio and sensor data freshness in real-time databases

Abstract

Abstract-The demand for real-time data services is increasing in many applications including e-commerce, agile manufacturing, and telecommunications network management. In these applications, it is desirable to execute transactions within their deadlines, i.e., before the real-world status changes, using fresh (temporally consistent) data. However, meeting these fundamental requirements is challenging due to dynamic workloads and data access patterns in these applications. Further, transaction timeliness and data freshness requirements may conflict. In this paper, we define average/transient deadline miss ratio and new data freshness metrics to let a database administrator specify the desired quality of real-time data services for a specific application. We also present a novel QoS management architecture for real-time databases to support the desired QoS even in the presence of unpredictable workloads and access patterns. To prevent overload and support the desired QoS, the presented architecture applies feedback control, admission control, and flexible freshness management schemes. A simulation study shows that our QoS-aware approach can achieve a near zero miss ratio and perfect freshness, meeting basic requirements for real-time transaction processing. In contrast, baseline approaches fail to support the desired miss ratio and/or freshness in the presence of unpredictable workloads and data access patterns.

Integrating Proactive and Reactive Approaches for Robust Real-Time Data Services

“…Based on H R , we can observe whether workloads exceed the operating range. Also, we intentionally generate bursty workloads that exceed H R to test the robustness of realtime data services under stress in Section V. Despite the importance, most existing work on feedback control of real-time data service performance, including [4], [3], [5], [6], [7], does not consider the reliability of real-time data services beyond the operating range.…”

“…To enhance the quality of real-time data services even in the presence of dynamic workloads, formal feedback control theory [1], [2] has been applied [3], [4], [5]. In these closed-loop approaches, system dynamics are approximated in a piecewise linear manner over a finite operating range of workloads for system modeling [1].…”

“…• As a result, the integrated approach is more adaptive to dynamic workloads compared to feedback-only approaches for real-time data services such as [4], [3], [5], [6], [7]. This is a key feature needed to improve the quality of real-time data services in dynamic environment.…”

“…We extend the Berkeley DB [8] (an open source database from Oracle) to support real-time data services via the feed-forward and feedback schemes. The tested workloads are not only within but also beyond the operating range to explore the system behaviors extensively, unlike most existing work on feedback control of real-time data services [4], [3], [5], [6], [7] that only considers workloads within the operating range. The open-loop approach, i.e., the unmodified Berkeley DB, and feed-forward-only approach based on the CLT fail to support the desired data service delay bound even for relatively light workloads.…”

An effective fixed priority co-scheduling algorithm for periodic update and application transactions

“…However, most of the proposed algorithms have ignored the impact on the scheduling of application transactions that are executed concurrently with the update transactions. Many of the previous works assumed that the application transactions are assigned lower priorities compared with the update transactions so that the scheduling of the application transactions will not affect the schedulability of the update transactions [13,19,33]. Although this assumption can simplify the co-scheduling problem, the performance of the application transactions could be severely affected as the workload of update transactions could be heavy in order to maintain the temporal validity of all the real-time data objects.…”