Legacy applications are typically monolithic, massive, and inflexible, comprising millions of lines of code. They are neither modular nor modern. It's very difficult to bring in any changes on particular portions of them. However, they have been contributing immensely in successfully running a majority of the business behemoths across the globe. Mainframe servers are the most powerful and high-performance IT infrastructures hosting and running a variety of complex legacy applications. Though mission-critical applications are being run on mainframes, modern-day computing mandates for a kind of marriage between mainframe computing and web-scale computing. That is, we need easily-manageable and -maintainable applications. On the infrastructure side, we need open, highly compartmentalized, programmable, optimized, and organized IT infrastructures.
Thus, there is a push for legacy applications to embrace the newly-introduced innovations in software engineering. There are many noteworthy architectural styles, process optimization techniques, and tools to speed up the transformation process. Digital transformation forces us to deliver faster. Every organization’s priority is to have well-designed
applications, the ability to deploy to on-premise and cloud environments as well as deploy independently, update services, and deploy defect fixes and new features in hours or days, not months.
In this chapter, we'll discuss how the microservices architecture (MSA) is the way forward for modern applications that are highly nimble, versatile, and resilient.
The chapter objectives include the following:
- Describing the needs for legacy application modernization
- Delineating why applications have to be modernized to be migrated and run in cloud environments
- Depicting how the combination of microservices and containers is the preferred one for legacy modernization
- Detailing the legacy modernization methodology