PERFORMANCE ENGINEERING IN SCRUM Balasubramanian, Infosys Technologies Limited This paper describes how performance engineering as a software discipline should be planned and executed in an agile development cycle. The intention of this paper is not to explain in detail the agile methodology or Performance engineering, even though it provides a high level description of the same. It is expected that the readers have a basic understanding of agile methodologies and performance engineering. Introduction Agile as a software development methodology is fast becoming a popular approach due to its ability to react to business changes. While there are still fears about adopting an agile approach to software development, the industry is clearly seeing a rise in agile adoption. Every year, thousands of dollars are being spent to fix poorly performing applications. This has made the software industry to relook at the way performance engineering is executed. A more proactive approach to architect and design for performance is now planned than a reactive post-mortem like approach. There needs to be a clear direction in identifying the various activities of performance engineering and executing them in logical sequence during an agile development process. This paper aims at suggesting one such approach by indicating various performance engineering activities across an agile development process. Overview of Agile Traditionally software has been developed using a waterfall approach. While this suited the initial days, as business complications grew and demand for time to market increased, waterfall model did not deliver the required results. Agile methodology was born out the need to respond to rapidly changing business requirements and deliver increments of shippable application with time to market as the primary focus. In the book, “Lean Software Development: An Agile Toolkit for Software Development Managers", Mary and Tom Poppendieck bring out the concept of eliminating waste in software projects. Agile as a methodology constantly looks at engaging the customer to prioritize scenarios that should be developed in each cycle, so as to eliminate waste. There have been many flavors of Agile developed over the past years. Agile Modeling, Scrum, Extreme Programming (XP) and Agile Unified Process (AUP) are some of the well known Agile Methodologies. For the context of this paper, we will analyze how performance engineering activities can be planned within a Scrum project cycle. Scrum – An Agile Methodology Scrum – A term derived from the game ‘rugby’, indicates a methodology of using small cross functional teams to deliver shippable software using cycles called sprints. This approach was described initially by Takeuchi and Nonaka, in the year 1986, and has been evolved into a widely practiced agile methodology. Figure 1: SCRUM Methodology The cores of the process are the sprints which are typically a 15-30 day period where the development team focuses on producing production ready software. The various phases of a scrum project are explained in the sections below. Planning and System Architecture Every Scrum project typically begins with this phase. Some of the activities in this phase are • Understanding the requirements • Developing the comprehensive list of backlog • Risk Assessment • Develop system architecture • Review architecture and develop high level design Sprints The goal of sprints is to develop shippable, production-quality application. Typically, there would be representation of all the activities of the SDLC lifecycle in each sprint. Note: It is not necessary that all sprints should have software as its deliverable. There are instances where a sprint would develop documentation like test scripts, user documentation etc. Closure This phase provides the team with the opportunity to view the complete application and have all sign off activities. A deep dive session into learning is also done during this phase. Overview of Performance Engineering Traditionally every software application has been tested and validated against the functional requirements. As we integrate more systems that are on various platforms, realized in various programming languages to serve a common need, we have built applications that are huge, that communicates across various layers and protocols. Performance Engineering is the discipline of SDLC that focuses on ensuring that applications are architected, designed, built and tested for performance. Performance engineering does not just involve reactive approaches like tuning, but focuses heavily on designing the application to deliver on SLA’s. A typical performance engineering activity would include • Collecting and validating the non functional requirements • Developing the required models for analysis • Developing a performance test strategy • Reviewing the architecture and application code to ensure compliance to performance best practices • Reviewing the deployment of the application, and • For pre-existing applications, reviewing the design and code to suggest appropriate tuning activities Why do we need Performance Engineering in SCRUM? Performance Engineering is an important activity for projects executed using any methodology. It becomes more critical for projects using SCRUM or any other agile methodology because of the following reasons Immediate feedback about system performance in each sprint Delivering production quality software during each sprint continuously is the crux of Scrum. In such a scenario, it is important to be able to receive feedback about the performance of the system as they are incrementally built in each sprint. It is a well known fact that the later issues are found, the costlier it is to fix them. It is easy to develop a false impression about performance Usually functional testing happens in a scaled down version of the environment with scaled down data. Clearly, performance is not the focus here and is normally ignored. This leads to the false impression that the application is performing well or will perform well. Also, in an agile methodology, functionalities and hence application code piles up with each cycle, and this leads to poorly performing code being injected into the system. What is more dangerous is the fact that it goes unnoticed. Refactoring may introduce code that performs poorly Evolving and fine tuning design is an inherent part of scrum. This leads to refactoring both framework components and application code. There might be instances when such refactoring can inject code that performs poorly. The goal is shippable, production quality code It is stressed enough that the every scrum works towards delivering a production quality application. Meeting the Quality of Service requirements is an absolute must for an application to be deemed production ready. Performance engineering ensures that an application is designed, built and validated against the required Quality of Service requirements. Hence the need for performance engineering is inherently built into Scrum. Performance Engineering Processes in Scrum This section will suggest various performance engineering activities that should be planned for and executed in the stages of scrum lifecycle. System Planning Sprints Closure Architecture Understand and Validate NFR’s Architecture Assessment – The NFR Identify and Plan Performance Tests Viewpoint Setup Performance Identify bottlenecks and fix Monitoring Systems Performance Test Strategy performance issues Identify Performance engineering Review Design and code activities in product backlog Figure 2: Performance Engineering In SCRUM Planning Stage This phase involves understanding the requirements, and planning for the ‘sprints’ ahead. The various performance engineering activities that should be planned during this phase are listed and explained below Use cases and Performance Assigning performance requirements to use cases will enable architects to understand the performance needs of various areas of the application from a functional perspective. This approach could also aid in obtaining sign off’s on various use cases on Quality of Service requirements. Understand and validate Non Functional Requirements This is an area everyone would agree is important and critical, but is the one often missed or partly done due to various constraints. Efforts spent here will help the team to validate the performance requirements and be realistic about it. Performance Test Strategy It is important to define the test strategy, which will include details like • Scope of Performance Testing • Infrastructure needs • Methodology used for testing • Workload characteristics used for testing • What are the tool requirements and licensing cost? • What are the metrics that are captured? • How will the results be shared? Identify Performance engineering activities in product backlog While we are identifying feature lists for the product backlog, it is also important to identify the various performance engineering activities like workload modeling, performance testing, performance assessment etc. Many a times these activities are inherently assumed and not planned, resulting in insufficient planning and poor execution. System Architecture Phase Defining architecture for the system determines the success of the code to meet the requirements. While there has been a lot of focus on validating the architecture for the various functional and business requirements, it is sad that reviewing architecture for NFR’s is not planned as a matter of priority. Architecture Assessment – The