Layered microservices architecture: A multitree-based domain-driven approach

Abstract

Context:

Domain-driven design is commonly used with microservices architecture to develop complex microservices-based software systems. Layered, tree-based microservices architectures have recently been discussed as a solution to tame the complexity of these systems. However, there exists a knowledge gap in terms of the exact nature of this architecture style and how it is constructed.

Objective:

In this paper, we propose a domain-driven multitree microservices architecture (TMSA) to bridge this gap.

Method:

We precisely define the TMSA metamodel in UML/OCL. A service is composed of a nested service tree, whose internal nodes are domain-driven modules. Service structure reuse is enabled by unidirectional edges that connect nodes in distinct service trees. The multitree structure provides a scaffolding on which to precisely define service resiliency and TMSA model evolution. We use OCL and the UML communication diagram to model the resiliency patterns and the architectural model evolution.

Results:

Our UML/OCL-based metamodel of TMSA provides a foundation on which to define three essential service resiliency patterns and two operators for architectural model evolution. To ease software construction, we further define an annotation-based DSL, named TASL, to specify the TMSA model and a semi-automatic procedure that takes a TASL specification as input and constructs software as the output. We demonstrate TMSA with an implementation in a Java software framework and a real-world software example. We also evaluate the performance, resiliency and modifiability of TMSA. The results show that TMSA possesses the expected levels of quality for these attributes.

Conclusion:

Our work provides not only a framework to identify and formally define multitree-based MSAs but a state-of-the-art realisation of this framework in high-level object-oriented programming languages.