PolyCert: Polymorphic Self-optimizing Replication for In-Memory Transactional Grids

Abstract

Abstract. In-memory NoSQL transactional data grids are emerging as an attractive alternative to conventional relational distributed databases. In these platforms, replication plays a role of paramount importance, as it represents the key mechanism to ensure data durability. In this work we focus on Atomic Broadcast (AB) based certification replication schemes, which have recently emerged as a much more scalable alternative to classical replication protocols based on active replication or atomic commit protocols. We first show that, among the existing AB-based certification protocols, no "one-fits-all" solution exists that achieves optimal performance in presence of heterogeneous workloads. Next, we present PolyCert, a polymorphic certification protocol that allows for the concurrent coexistence of different certification protocols, relying on machine-learning techniques to determine the optimal certification scheme on a per transaction basis. We design and evaluate two alternative oracles, based on parameter-free machine learning techniques that rely both on off-line and on-line training approaches. Our experimental results demonstrate the effectiveness of the proposed approach, highlighting that PolyCert is capable of achieving a performance extremely close to that of an optimal non-adaptive certification protocol in presence of non heterogeneous workloads, and significantly outperform any non-adaptive protocol when used with realistic, complex applications that generate heterogeneous workloads.

Bidding Strategies in QoS-Aware Cloud Systems Based on N-Armed Bandit Problems

“…Learning strategies alternative to our approach were also proposed in [6] (defining competitive behavior as a conjectural equilibrium), [7] (focusing on cooperation strategies), [8] (based on a stochastic game framework) and [9], [10] (optimizing performance of distributed platforms via banditbased RL algorithms).…”

Self-Tuning Transactional Data Grids: The Cloud-TM Approach

“…Regarding the replication protocol, we are aware of only two solutions that encompass its self-tuning, namely HTR [12] and PolyCert [13]. In both, the most appropriate protocol to validate the transaction with is determined on a per-transaction basis.…”

“…However, the self-tuning of any other platforms' parameters is at least uncommon for commercial platforms (at least based on available documentation [9], [10]). On the other hand, academic solutions for self-tuning of cloud data stores [11], [12], [13] target individual platform's parameters, failing to capture the strong intertwining between them (e.g., the choice of the replication protocol is clearly dependent on the platform's scale and on the number of data replicas stored in the platform). The Cloud-TM platform, conversely, takes a unique approach to self-tuning, based on two principles:…”

Elastic, scalable and self-tuning data replication in the cloud-TM platform

“…However, as I will show, among the existing AB-based certification protocols, no"one-fits-all" solution exists that achieves optimal performance in presence of heterogeneous workloads. Next, I will present PolyCert [5], a polymorphic data replication protocol that allows…”