An Industrial Experience Report on Performance-Aware Refactoring on a Database-Centric Web Application.

Modern web applications rely heavily on databases to query and update information. To ease the development efforts, Object Relational Mapping (ORM) frameworks provide an abstraction for developers to manage databases by writing in the same Object-Oriented programming languages. Prior studies have shown that there are various types of performance issues caused by inefficient accesses to databases via different ORM frameworks (e.g., Hibernate and ActiveRecord). However, it is not clear whether the reported performance anti-patterns (common performance issues) can be generalizable across various frameworks. In particular, there is no study focusing on detecting performance issues for applications written in PHP, which is the choice of programming languages for the majority (79%) of web applications. In this experience paper, we detail our process on conducting performance-aware refactoring of an industrial web application written in Laravel, the most popular web framework in PHP. We have derived a complete catalog of 17 performance anti-patterns based on prior research and our experimentation. We have found that some of the reported anti-patterns and refactoring techniques are framework or programming language specific, whereas others are general. The performance impact of the anti-pattern instances are highly dependent on the actual usage context (workload and database settings). When communicating the performance differences before and after refactoring, the results of the complex statistical analysis may be sometimes confusing. Instead, developers usually prefer more intuitive measures like percentage improvement. Experiments show that our refactoring techniques can reduce the response time up to 93.0% and 93.4% for the industrial and the open source application under various scenarios.