Abstract
ContextMicroservices as a lightweight and decentralized architectural style with fine-grained services promise several beneficial characteristics for sustainable long-term software evolution. Success stories from early adopters like Netflix, Amazon, or Spotify have demonstrated that it is possible to achieve a high degree of flexibility and evolvability with these systems. However, the described advantageous characteristics offer no concrete guidance and little is known about evolvability assurance processes for microservices in industry as well as challenges in this area. Insights into the current state of practice are a very important prerequisite for relevant research in this field.ObjectiveWe therefore wanted to explore how practitioners structure the evolvability assurance processes for microservices, what tools, metrics, and patterns they use, and what challenges they perceive for the evolvability of their systems.MethodWe first conducted 17 semi-structured interviews and discussed 14 different microservice-based systems and their assurance processes with software professionals from 10 companies. Afterwards, we performed a systematic grey literature review (GLR) and used the created interview coding system to analyze 295 practitioner online resources.ResultsThe combined analysis revealed the importance of finding a sensible balance between decentralization and standardization. Guidelines like architectural principles were seen as valuable to ensure a base consistency for evolvability and specialized test automation was a prevalent theme. Source code quality was the primary target for the usage of tools and metrics for our interview participants, while testing tools and productivity metrics were the focus of our GLR resources. In both studies, practitioners did not mention architectural or service-oriented tools and metrics, even though the most crucial challenges like Service Cutting or Microservices Integration were of an architectural nature.ConclusionsPractitioners relied on guidelines, standardization, or patterns like Event-Driven Messaging to partially address some reported evolvability challenges. However, specialized techniques, tools, and metrics are needed to support industry with the continuous evaluation of service granularity and dependencies. Future microservices research in the areas of maintenance, evolution, and technical debt should take our findings and the reported industry sentiments into account.
Highlights
Fast moving markets and the age of digitalization require that software can be quickly adapted or extended with new features
We discussed 14 systems (S1–S14) and their evolvability assurance processes, where in three cases, two participants talked about the same system (S5, S9, S11)
Similar as with the interviews, we present the grey literature review (GLR) results in three subsections that correspond to our research questions
Summary
Fast moving markets and the age of digitalization require that software can be quickly adapted or extended with new features. The quality attribute associated with software evolution is referred to as evolvability (Rowe et al 1998): the degree of effectiveness and efficiency with which a system can be adapted or extended. For Rajlich (2018), evolvability is more demanding and requires maintainability, i.e. an evolvable system is always maintainable but not vice versa. In this sense, it is impossible to evolve unmaintainable software, yet maintaining software that can no longer be evolved may still be possible. Evolvability is especially important for software with frequently changing requirements, e.g. internet-based systems
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