Lorq: A System for Replicated NoSQL Data Based on Consensus Quorum
[ 1 ] Instytut Automatyki i Inżynierii Informatycznej, Wydział Elektryczny, Politechnika Poznańska | [ P ] employee
2016
paper
english
EN In this paper, we discuss a system, called Lorq, for NoSQL data replication. Data replication in the system is based on replication of logs storing update and some control operations. It is guarantied that operations in all logs are eventually applied to their databases in the same order. However, due to possible latency and failures, the time of the application can be different, leading to different levels of consistencies. Applications have possibilities to declare their consistency and latency priorities, from strong consistency to a kind of weak consistencies. In this way, the server level agreement (SLA) is provided. To guarantee strong consistency, a consensus quorum algorithm is used meaning that an update (read) operation is treated successful if a write (read) consensus quorum is reached. Strong consistency ensures that the most up-to-date data is read. To guarantee a weaker consistency, Lorq algorithm utilizes timestamps, which are assigned to both data objects and databases. These timestamps are updated along with update and control operations performed over databases. The algorithm enforce dynamic selection of servers accessed by read operations to ensure required level of consistency and payment depending on consistency level.
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