Exploring Maintainability Assurance Research for Service- and Microservice-Based Systems: Directions and Differences

To ensure sustainable software maintenance and evolution, a diverse set of activities and concepts like metrics, change impact analysis, or antipattern detection can be used. Special maintainability assurance techniques have been proposed for service- and microservice-based systems, but it is difficult to get a comprehensive overview of this publication landscape. We therefore conducted a systematic literature review (SLR) to collect and categorize maintainability assurance approaches for service-oriented architecture (SOA) and microservices. Our search strategy led to the selection of 223 primary studies from 2007 to 2018 which we categorized with a threefold taxonomy: a) architectural (SOA, microservices, both), b) methodical (method or contribution of the study), and c) thematic (maintainability assurance subfield). We discuss the distribution among these categories and present different research directions as well as exemplary studies per thematic category. The primary finding of our SLR is that, while very few approaches have been suggested for microservices so far (24 of 223, ?11%), we identified several thematic categories where existing SOA techniques could be adapted for the maintainability assurance of microservices

Road to Microservices

This document intends to elucidate the complexity of microservices decomposition and this its inherent process of implementation. Developments in technology and design, achieving higher performance, reliability, or lowering costs are valid reasons to consider controlling the product’s quality by guaranteeing its conformance with established characteristics and standards. Control is made possible by adding quality control, inspection routines, and trend analysis to a manufacturing process. These techniques are established in the Quality field academically and business-wise. Repeat Part Management (RPM) is software that allows users to apply these techniques efficiently and has brought value to the company. However, RPM has been growing, and issues have emerged due to customer needs - accumulated technical debt. These ever-growing modifications are common through different business areas, and architectures’ research evolution has accompanied them. This demand for highly modifiable, rapid development, and independent systems has resulted in the adoption of microservices. There is a concern for existing systems for decomposition due to the characteristics of microservices, which encourages approach/technique research. This architecture promotes legacy system analysis to map current functionalities and dependencies between components. Furthermore, critical concepts in a microservices architecture are researched and implemented in a new system that encompasses Repeat Part Management’s functionalities. This thesis explores the microservices’ architecture evolution with an already defined mature domain in quality assessment.Este documento pretende especificar a complexidade do processo de decomposição em microsserviços e do seu processo de implementação. Avanços na tecnologia e design, alcançar melhor performance, ou a confiabilidade do produto, ou diminuir custos são justificações válidas para considerar controlar a qualidade do produto e, inerentemente, garantir a sua conformidade com as características previamente definidas e com padrões da indústria. É possível garantir controlo sob os produtos ao acrescentar, ao processo produtivo, métodos de controlo de qualidade, rotinas de inspeção e análise de tendências (de desvio). Estas técnicas estão bem estabelecidas academicamente e, de um ponto de vista do mercado, na área da Qualidade e garantia da qualidade. O Repeat Part Management (RPM) é um software que permite aos seus utilizadores a utilização eficiente destas técnicas de qualidade, o que resulta numa adição de valor para a empresa. Porém, devido às crescentes necessidades dos clientes, alguns problemas têm sido identificados - relacionados com o conceito de acumulação de technical debt. Esta crescente necessidade de alteração é comum em diversas áreas de negócio, e a investigação de soluções arquiteturais tem acompanhado esta pesquisa. Esta solução arquitetura pode ser caracterizada pela facilidade de sistemas facilmente modificáveis, pelo rápido desenvolvimento e implementação, e pela independência dos serviços decompostos. Aquando de uma migração para microsserviços num sistema maturo, existe uma maior preocupação na decomposição da aplicação e definição dos serviços dada a característica dos microsserviços, o que incentiva a uma pesquisa detalhada sobre as técnicas de decomposição. Pela mesma razão, esta arquitetura incentiva ao mapeamento e documentação das dependências entre serviços e componentes e o estudo da aplicação legacy. Para além disto, estes conceitos, e a sua implementação devem ser planeados, justificados e documentados, o que explica a complexidade do processo de migração e implementação, que deve ter em consideração as funcionalidades existentes no Repeat Part Management. Dessa forma, esta tese explora a implementação desta arquitetura numa aplicação matura na área de Garantia de Qualidade

Identification of microservices from monolithic applications through topic modelling

Microservices emerged as one of the most popular architectural patterns in the recent years given the increased need to scale, grow and flexibilize software projects accompanied by the growth in cloud computing and DevOps. Many software applications are being submitted to a process of migration from its monolithic architecture to a more modular, scalable and flexible architecture of microservices. This process is slow and, depending on the project’s complexity, it may take months or even years to complete. This paper proposes a new approach on microservice identification by resorting to topic modelling in order to identify services according to domain terms. This approach in combination with clustering techniques produces a set of services based on the original software. The proposed methodology is implemented as an open-source tool for exploration of monolithic architectures and identification of microservices. A quantitative analysis using the state of the art metrics on independence of functionality and modularity of services was conducted on 200 open-source projects collected from GitHub. Cohesion at message and domain level metrics’ showed medians of roughly 0.6. Interfaces per service exhibited a median of 1.5 with a compact interquartile range. Structural and conceptual modularity revealed medians of 0.2 and 0.4 respectively. Our first results are positive demonstrating beneficial identification of services due to overall metrics’ resultsNational Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia within project UIDB/50014/202

Defining Metrics for the Identification of Microservices in Code Repositories

Microsserviços tornaram-se o estilo de arquitetura mais utilizado entre todas as estratégias de desenvolvimento de software disponíveis. No entanto, as pesquisas sobre esse tema estão no início, o que dificulta a localização de aplicações de microsserviços em escala para análise. Portanto, há uma grande necessidade de novas investigações, bem como ferramentas para apoiar novos desenvolvimentos no campo de microsserviços. O primeiro objetivo deste trabalho é coletar características de microsserviços encontradas na literatura e traduzi-las em características mensuráveis no código. Com isso, fornecemos um conjunto abrangente de características, bem como métricas para identificá-las no código. Um segundo objetivo é usar essas métricas para identificar a base do código seguindo um estilo de arquitetura de microsserviço. Essa solução é disponibilizada por meio de uma ferramenta que permite aos usuários encontrar microsserviços em escalas e filtrá-los de acordo com suas necessidades. Isso pode ser usado para encontrar exemplos de microsserviços em uma linguagem de programação específica ou para criar corpora para estudos de pesquisa. Nossa avaliação mostra que nosso algoritmo pode identificar microsserviços com uma precisão de 85%.Microservices have become the most used architectural style among all available software development strategies. However, it is difficult to find microservice applications at scale for analysis. Therefore, there is a great need for new investigations as well as tools to support new developments in the field of microservices. The first goal of this work is to collect microservices characteristics found in the literature and translate them into measurable features in the code. With this, we provide a comprehensive set of characteristics as well as metrics to identify them in the code. A second goal is to design an algorithm to use such metrics to identify code basis following a microservice architectural style. This solution is made available through a tool that allows users to find microservices at scales and filter them according to their needs. This can be used to find examples of microservices in a specific programming language or to create corpora for research studies. Our evaluation shows our algorithm can identify microservices with a precision of 85%

Identification of microservices from monolithic applications through topic modelling

Dissertação de mestrado em Informatics EngineeringMicroservices emerged as one of the most popular architectural patterns in the recent years given the increased need to scale, grow and flexibilize software projects accompanied by the growth in cloud computing and DevOps. Many software applications are being submitted to a process of migration from its monolithic architecture to a more modular, scalable and flexible architecture of microservices. This process is slow and, depending on the project’s complexity, it may take months or even years to complete. This dissertation proposes a new approach on microservices identification by resorting to topic modelling in order to identify services according to domain terms. This approach in combination with clustering techniques produces a set of services based on the original software. The proposed methodology is implemented as an open-source tool for exploration of monolithic architectures and identification of microservices. An extensive quantitative analysis using the state of the art metrics on independence of functionality and modularity of services was conducted on 200 open-source projects collected from GitHub. Cohesion at message and domain level metrics showed medians of roughly 0.6. Interfaces per service exhibited a median of 1.5 with a compact interquartile range. Structural and conceptual modularity revealed medians of 0.2 and 0.4 respectively. Further analysis to understand if the methodology works better for smaller/larger projects revealed an overall stability and similar performance across metrics. Our first results are positive demonstrating beneficial identification of services due to overall metrics’ results.Os microserviços emergiram como um dos padrões arquiteturais mais populares na atualidade dado o aumento da necessidade em escalar, crescer e flexibilizar projetos de software, acompanhados da crescente da computação na cloud e DevOps. Muitas aplicações estão a ser submetidas a processos de migração de uma arquitetura monolítica para uma arquitetura mais modular, escalável e flexivel de microserviços. Este processo de migração é lento, e dependendo da complexidade do projeto, poderá levar vários meses ou mesmo anos a completar. Esta dissertação propõe uma nova abordagem na identificação de microserviços recorrendo a modelação de tópicos de forma a identificar serviços de acordo com termos de domínio de um projeto de software. Esta abordagem em combinação com técnicas de clustering produz um conjunto de serviços baseado no projeto de software original. A metodologia proposta é implementada como uma ferramenta open-source para exploração de arquiteturas monolíticas e identificação de microserviços. Uma análise quantitativa extensa recorrendo a métricas de independência de funcionalidade e modularidade de serviços foi conduzida em 200 aplicações open-source recolhidas do GitHub. Métricas de coesão ao nível da mensagem e domínio revelaram medianas em torno de 0.6. Interfaces por serviço demonstraram uma mediana de 1.5 com um intervalo interquartil compacto. Métricas de modularidade estrutural e conceptual revelaram medianas de 0.2 e 0.4 respetivamente. Uma análise mais aprofundada para tentar perceber se a metodologia funciona melhor para projetos de diferentes dimensões/características revelaram uma estabilidade geral do funcionamento do método. Os primeiros resultados são positivos demonstrando identificações de serviços benéficos tendo em conta que os valores das métricas são de uma forma global positivos e promissores

Technical Challenges of Microservices Migration

The microservices architecture is a recent trend in the software engineering community, with the number of research articles in the field increasing, and more companies adopting the architectural style every year. However, the migration of a monolith to the microservices architecture is an error-prone process with a lack of guidelines for its execution. Also, microservices introduce a lot of different challenges that are not faced when following a monolithic architecture. This work aims to fill some gaps in current microservices research by providing a catalogue of the currently most common challenges of adopting this architectural style, and possible solutions for them. For this reason, a systematic mapping study was executed analysing 54 different articles. Also, 30 industry professionals participated in a questionnaire regarding the topic. Furthermore, a participant observation experiment was performed to retrieve additional industry data. Moreover, one of the identified challenges – distributed transactions management – was further detailed and a solution implemented using the choreographed saga pattern. The solution is publicly available as an open-source project. Finally, multiple experts in the microservices field validated the results of the research and the distributed transactions solution and provided insights regarding the value of this work.A arquitetura de microserviços é uma tendência recente na comunidade de engenharia de software, com o número de artigos publicados sobre o tema a aumentar, assim como o número de empresas a adoptar o estilo arquitetural todos os anos. No entanto, o processo de migração de um monolito para uma arquitetura orientada a microserviços tem um alto potencial de erros, uma vez que existe falta de orientações sobre como conduzir o processo corretamente. Para além disso, os microserviços introduzem muitos desafios diferentes que não são enfrentados no desenvolvimento de um sistema monolitico. Este trabalho pretende preencher algumas destas lacunas na investigação da arquitetura de microserviços através da construção de um catalogo dos principais desafios enfrentados ao adoptar o estilo arquitetural e soluções possíveis para estes. Por este motivo, um systematic mapping study foi desenvolvido, analisando 54 artigos diferentes. Para além disso, 30 profissionais da industria responderam a questionario sobre o tema. Finalmente, para obter dados adicionais da indústria, uma experiência de migração foi realizada e observada de forma ativa. Ainda, um dos desafios identificados – gestão de transações distribuídas – foi detalhado e uma solução implementada usando o padrão de sagas coreografadas. A solução está publicamente disponível como um projecto open-source. Finalmente, vários peritos em microserviços avaliaram os resultados deste trabalho, incluindo a solução desenvolvida para gestão de transações distribuídas, e deram feedback relativamente ao valor deste trabalho

From Monolith to Microservices: A Classification of Refactoring Approaches

While the recently emerged Microservices architectural style is widely discussed in literature, it is difficult to find clear guidance on the process of refactoring legacy applications. The importance of the topic is underpinned by high costs and effort of a refactoring process which has several other implications, e.g. overall processes (DevOps) and team structure. Software architects facing this challenge are in need of selecting an appropriate strategy and refactoring technique. One of the most discussed aspects in this context is finding the right service granularity to fully leverage the advantages of a Microservices architecture. This study first discusses the notion of architectural refactoring and subsequently compares 10 existing refactoring approaches recently proposed in academic literature. The approaches are classified by the underlying decomposition technique and visually presented in the form of a decision guide for quick reference. The review yielded a variety of strategies to break down a monolithic application into independent services. With one exception, most approaches are only applicable under certain conditions. Further concerns are the significant amount of input data some approaches require as well as limited or prototypical tool support.Comment: 13 pages, 4 tables, 2 figures, Software Engineering Aspects of Continuous Development and New Paradigms of Software Production and Deployment, First International Workshop, DEVOPS 2018, Chateau de Villebrumier, France, March 5-6, 2018, Revised Selected Paper

Understanding the Issues, Their Causes and Solutions in Microservices Systems: An Empirical Study

Many small to large organizations have adopted the Microservices Architecture (MSA) style to develop and deliver their core businesses. Despite the popularity of MSA in the software industry, there is a limited evidence-based and thorough understanding of the types of issues (e.g., errors, faults, failures, and bugs) that microservices system developers experience, the causes of the issues, and the solutions as potential fixing strategies to address the issues. To ameliorate this gap, we conducted a mixed-methods empirical study that collected data from 2,641 issues from the issue tracking systems of 15 open-source microservices systems on GitHub, 15 interviews, and an online survey completed by 150 practitioners from 42 countries across 6 continents. Our analysis led to comprehensive taxonomies for the issues, causes, and solutions. The findings of this study inform that Technical Debt, Continuous Integration and Delivery, Exception Handling, Service Execution and Communication, and Security are the most dominant issues in microservices systems. Furthermore, General Programming Errors, Missing Features and Artifacts, and Invalid Configuration and Communication are the main causes behind the issues. Finally, we found 177 types of solutions that can be applied to fix the identified issues. Based on our study results, we formulated future research directions that could help researchers and practitioners to engineer emergent and next-generation microservices systems.Comment: 35 pages, 5 images, 7 tables, Manuscript submitted to a Journal (2023