Scalable and Transactional Actor-Oriented Databases

In modern system design, the ”separation of concerns” principle has led to two
significant architectural trends: a shift from stateless to stateful middle tiers in
the three-tier client-server architecture and the growing adoption of modular,
loosely coupled architectures for complex applications. These trends enhance
system responsiveness, scalability, and flexibility but also present challenges.
The rising popularity of stateful middle-tier architectures, which maintain
application states close to application logic in the middle-tier servers, offers
numerous benefits but transfers the complexity of state management from
backend databases to the application layer. In addition, it is particularly
challenging to manage distributed states across loosely coupled components.
The actor model [4] has experienced a resurgence as a tool for building
stateful middle tiers and modular systems. By breaking down application
logic into independent actors that communicate asynchronously, the actor
model simplifies concurrency, scalability, and system resource management.
However, its adoption has been limited due to the absence of critical database
features such as transaction management, data replication, and data con-
straint enforcement. In response, the Actor-Oriented Database (AODB) [30]
concept has emerged, proposing integrating these database capabilities into
actor-based systems.
This dissertation emphasizes the need for further research and development in AODB. Specifically, we propose a scalable and transactional AODB to address the state management challenges for actor-based stateful middle tiers of modern applications. This dissertation achieves the goal through three steps: developing a transaction library for multi-actor transactions, designing a distributed system architecture, and introducing a data model to enable finer-grained state management. The outcome of this dissertation is a fully developed AODB featuring a clear and expressive programming model, a scalable actor-oriented architecture, efficient transaction processing techniques, a prototype implementation built on the Orleans framework, and comprehensive cloud-based evaluation.