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From Code Refactoring to API Refactoring: Agile Service Design and Evolution

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Service-Oriented Computing (SummerSOC 2021)

Part of the book series: Communications in Computer and Information Science ((CCIS,volume 1429))

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Abstract

Refactoring is an essential agile practice; microservices are a currently trending implementation approach for service-oriented architectures. While program-internal code refactoring is well established, refactoring components on the architectural level has been researched but not adopted widely in practice yet. Hence, refactoring service Application Programming Interfaces (APIs) is not understood well to date. As a consequence, practitioners struggle with the evolution of APIs exposed by microservices. To overcome this problem, we propose to switch the refactoring perspective from implementation to integration and study how refactorings can be applied to the problem domain of agile service API design and evolution. We start with an empirical analysis and assessment of the state of the art and the practice. The contributions of this paper then are: 1) presentation of results from a practitioner survey on API change and evolution, 2) definitions for a future practice of API refactoring and 3) a candidate catalog of such API refactorings. We discuss these contributions and propose a research action plan as well.

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Notes

  1. 1.

    http://www.syncdev.com/minimum-viable-product/.

  2. 2.

    http://wirfs-brock.com/blog/2011/01/18/agile-architecture-myths-2-architecture-decisions-should-be-made-at-the-last-responsible-moment/.

  3. 3.

    https://martinfowler.com/articles/injection.html.

  4. 4.

    https://aws.amazon.com/architecture/well-architected.

  5. 5.

    https://docs.microsoft.com/en-us/azure/architecture/framework.

  6. 6.

    https://stackoverflow.com/.

  7. 7.

    https://www.microsoft.com/en-us/servicesagreement/default.aspx.

  8. 8.

    http://www.jamesshore.com/v2/blog/2005/red-green-refactor.

  9. 9.

    One might argue that this violates the original definition of refactoring because the observable behavior is clearly and deliberately changed. In the refactoring example given earlier, a local variable is renamed, making it unlikely that the observable behavior of the software changes. But refactorings involving multiple classes, for example moving a method from one class to another, change the interfaces of these classes – possibly including public ones – in a backwards-incompatible manner. Whether this constitutes observable behavior depends on the viewpoint and expectations of the observer: an API client developer might notice and be directly affected by the change, but not the end user of the software. It has been shown that behavior-changing modifications still qualify as refactorings [11].

  10. 10.

    https://www.microservice-api-patterns.org, also see [15, 22, 30, 31, 33].

  11. 11.

    At https://interface-refactoring.github.io we have started to publish these refactorings; names and content of the refactoring are subject to change.

  12. 12.

    Only include a pattern if there are at least three known uses. Not to be confused with the “rule of three” of refactoring [6] duplicated pieces of code, where it refers to the number of duplicates starting from which a refactoring is recommended.

  13. 13.

    www.ozimmer.ch/practices/2021/03/05/POINTPrinciplesForAPIDesign.html.

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Acknowledgments

We would like to thank all reviewers and participants of the survey. The work of Mirko Stocker and Olaf Zimmermann is supported by the Hasler Foundation through grant nr. 21004.

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  1. University of Applied Sciences of Eastern Switzerland (OST), Oberseestrasse 10, 8640, Rapperswil, Switzerland

    Mirko Stocker & Olaf Zimmermann

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  1. Mirko Stocker
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Correspondence to Mirko Stocker .

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  1. University of Stuttgart, Stuttgart, Germany

    Johanna Barzen

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Stocker, M., Zimmermann, O. (2021). From Code Refactoring to API Refactoring: Agile Service Design and Evolution. In: Barzen, J. (eds) Service-Oriented Computing. SummerSOC 2021. Communications in Computer and Information Science, vol 1429. Springer, Cham. https://doi.org/10.1007/978-3-030-87568-8_11

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  • DOI: https://doi.org/10.1007/978-3-030-87568-8_11

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