Software architecture (SA) has a prominent role in all stages of system development. Given the persistent evolution of software systems over time, SA tends to be eroded or degraded. Such phenomenon is called architectural degradation. In light of this phenomenon, the current study focuses on problems of architectural erosion in the open-source software (OSS). There has been a significant research activity on the OSS over the last decade. Nonetheless, the architectural degradation problems in the OSS are still scattered and disorganized. In addition, there has been no systematic attempt made on existing studies to provide evidence, insight and better understanding for researchers and practitioners. The main objective of the present study is to provide a profound understanding and to review the existing studies on the architectural erosion of the OSS. In this study, we conduct a systematic literature review (SLR) to gather, organize, classify, and analyze the architectural degradation of previous papers published until the year 2020. The data for this study were collected from eight major online databases (ACM, Springer, ScienceDirect, Taylor, IEEE Explorer, Scopus, Web of Science, and Wiley). A total of 74 primary studies were identified as the final samples of this research. The results indicated that rapid software evolution, frequent changes, and the lack of developers' awareness are the most common causes occurred in architecture degradation. Meanwhile, the prominent key indicators of architectural erosion symptoms are code smells and architectural smells. Additionally, the results indicated the most commonly used of the proposed solution for addressing architectural erosion is the metrics-based strategy. Acknowledging the limitations of the current study, more studies are needed that focus on determining other causes that are still ambiguous and improving the other solutions to provide better results in the precision and effectiveness of addressing architectural erosion.

Software architecture is crucial in determining success or failure in a variety of software development and design fields. Typically, as a system evolves, software architecture deteriorates. This phenomenon is known as architectural erosion. Several studies have addressed architectural erosion based on different solutions. As a result, the metrics technique is the most prevalent solution for architectural erosion. Nevertheless, a comprehensive description of architectural erosion metrics remains unorganized and scattered. This work aims to conduct a systematic mapping to describe and analyze the architectural erosion metrics to provide an overview of erosion metrics and their current trends. Furthermore, no systematic attempts have been made on architectural erosion metrics. The final samples of this study were specified as a total of 43 included papers. Nearly 100 architectural erosion metrics were found. We proposed nine classifications to address architectural erosion challenges, based on adopted approaches in primary studies. The metrics of architectural erosion provide strong evidence for identifying decay and a rapid enabler factor for the adoption of numerous metrics mechanisms to address architectural erosion. The classification of metrics, which is the first of its kind, benefits researchers and practitioners. However, it can be concluded that various aspects are still ambiguous and require further research on architectural erosion measures.

This decay does not happen overnight, but rather it's cumulative impacts over time. Even though the prior works covered various aspects concerning maintaining architecture from erosion, however, the common factor in the existing studies does not provide full detail about the empirical analysis, perceptions of the proposed approaches, and trendy track of the architectural decay research. There are existing review studies on analysis techniques and approaches of various architectural decay, but to the best of our knowledge, insufficient focus was considered on precisely the description of the empirical analysis, techniques, approaches, and trends for studies that have been evaluated concerning architectural decay. This study provides a comprehensive survey and detailed investigation on the empirical analysis regarding research design and its method, existing approaches analysis to identify used strategies, and trendy research to clarify trendy track for researchers and what evolves from a meaningful essential idea concerns the researchers within the architectural degradation field.