Collecting Service-Based Maintainability Metrics from RESTful API Descriptions: Static Analysis and Threshold Derivation

TL;DR

This paper introduces RAMA, a modular tool for automatically collecting maintainability metrics from RESTful API descriptions, providing thresholds for assessing service quality, and demonstrated on over 1,700 APIs.

Contribution

The paper presents RAMA, a novel, extensible approach and tool for static analysis of RESTful APIs to derive maintainability metrics and establish threshold ranges.

Findings

RAMA successfully analyzed 1,737 RESTful APIs.

It derived threshold ranges for maintainability metrics.

The approach supports empirical evaluation of service interfaces.

Abstract

While many maintainability metrics have been explicitly designed for service-based systems, tool-supported approaches to automatically collect these metrics are lacking. Especially in the context of microservices, decentralization and technological heterogeneity may pose challenges for static analysis. We therefore propose the modular and extensible RAMA approach (RESTful API Metric Analyzer) to calculate such metrics from machine-readable interface descriptions of RESTful services. We also provide prototypical tool support, the RAMA CLI, which currently parses the formats OpenAPI, RAML, and WADL and calculates 10 structural service-based metrics proposed in scientific literature. To make RAMA measurement results more actionable, we additionally designed a repeatable benchmark for quartile-based threshold ranges (green, yellow, orange, red). In an exemplary run, we derived thresholds for all RAMA CLI metrics from the interface descriptions of 1,737 publicly available RESTful APIs. Researchers and practitioners can use RAMA to evaluate the maintainability of RESTful services or to support the empirical evaluation of new service interface metrics.