Adaptation through replica-group reconfiguration in NoSQL data stores (Master thesis)

Βαλεκάρδας, Δημήτριος

Modern stateful services are able to adapt by dynamically adjusting the level of fault tolerance and performance to ensure that their service characteristics closely match user requirements, which may change over time. In this thesis we focus on adaptive stateful services using replicated NoSQL (key-value) stores for maintaining state, and on replica-group reconfiguration as the primary way to adjust the level of fault tolerance and performance delivered by each replica group in the system. We extend the state of the art in this field by considering the pros and cons of different ways to reconfigureareplicagroupandbyexperimentallyevaluatingreconfigurationvariants in the context of the Etcd key-value store, based on the Raft algorithm. We experimentally study the costs and benefits of replica-group reconfiguration in various adaptation scenarios of practical interest, using an implementation of Etcd extended with the joint-consensus reconfiguration method, as well as the default single-server reconfiguration offered in the publicly available implementation. Our results demonstrate that the main adaptation costs incurred in both reconfiguration variants are transferring state and electing a new leader. Reconfiguration actions may be scheduled to reduce either the duration or the performance impact of reconfiguration. In both cases the two variants perform comparably, differing only in qualitative aspects such as implementation complexity.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Πολυτεχνική Σχολή. Τμήμα Μηχανικών Ηλεκτρονικών Υπολογιστών και Πληροφορικής
Subject classification: Data storage
Keywords: Data storage
Appears in Collections:Διατριβές Μεταπτυχιακής Έρευνας (Masters)

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