Towards Performance and Dependability Benchmarking of Distributed Fault Tolerance Protocols. (Performance et fiabilité des protocoles de tolérance aux fautes)

In the modern era of on-demand ubiquitous computing, where applications and services are deployed in well-provisioned, well-managed infrastructures, administered by large groups of cloud providers such as Amazon, Google, Microsoft, Oracle, etc., performance and dependability of the systems have become primary objectives.Cloud computing has evolved from questioning the Quality-of-Service (QoS) making factors such as availability, reliability, liveness, safety and security, extremely necessary in the complete definition of a system. Indeed, computing systems must be resilient in the presence of failures and attacks to prevent their inaccessibility which can lead to expensive maintenance costs and loss of business. With the growing components in cloud systems, faults occur more commonly resulting in frequent cloud outages and failing to guarantee the QoS. Cloud providers have seen episodic incidents of arbitrary (i.e., Byzantine) faults where systems demonstrate unpredictable conducts, which includes incorrect response of a client's request, sending corrupt messages, intentional delaying of messages, disobeying the ordering of the requests, etc.This has led researchers to extensively study Byzantine Fault Tolerance (BFT) and propose numerous protocols and software prototypes. These BFT solutions not only provide consistent and available services despite arbitrary failures, they also intend to reduce the cost and performance overhead incurred by the underlying systems. However, BFT prototypes have been evaluated in ad-hoc settings, considering either ideal conditions or very limited faulty scenarios. This fails to convince the practitioners for the adoption of BFT protocols in a distributed system. Some argue on the applicability of expensive and complex BFT to tolerate arbitrary faults while others are skeptical on the adeptness of BFT techniques. This thesis precisely addresses this problem and presents a comprehensive benchmarking environment which eases the setup of execution scenarios to analyze and compare the effectiveness and robustness of these existing BFT proposals.Specifically, contributions of this dissertation are as follows.First, we introduce a generic architecture for benchmarking distributed protocols. This architecture, comprises reusable components for building a benchmark for performance and dependability analysis of distributed protocols. The architecture allows defining workload and faultload, and their injection. It also produces performance, dependability, and low-level system and network statistics. Furthermore, the thesis presents the benefits of a general architecture.Second, we present BFT-Bench, the first BFT benchmark, for analyzing and comparing representative BFT protocols under identical scenarios. BFT-Bench allows end-users evaluate different BFT implementations under user-defined faulty behaviors and varying workloads. It allows automatic deploying these BFT protocols in a distributed setting with ability to perform monitoring and reporting of performance and dependability aspects. In our results, we empirically compare some existing state-of-the-art BFT protocols, in various workloads and fault scenarios with BFT-Bench, demonstrating its effectiveness in practice.Overall, this thesis aims to make BFT benchmarking easy to adopt by developers and end-users of BFT protocols.BFT-Bench framework intends to help users to perform efficient comparisons of competing BFT implementations, and incorporating effective solutions to the detected loopholes in the BFT prototypes. Furthermore, this dissertation strengthens the belief in the need of BFT techniques for ensuring correct and continued progress of distributed systems during critical fault occurrence.