Unraveling the Strangler Pattern (Part II): 3 Phases of Planning & Analysis
Although the Strangler pattern can be helpful for IT infrastructure migrations and transitions, it’s not without its risks. Most of these challenges, however, come from haphazard decisions, underestimated complexities, and uncoordinated actions.
In other words, effectively implementing the Strangler pattern approach requires careful planning and analysis.
This article, a continuation of our six-part “Unraveling the Strangler Pattern” series, will move from the foundations of the architectural pattern into its practical application. We’ll discuss the three phases of strategic planning and why each one is critical to the success of this methodology.
Quick Recap: What is the Strangler Pattern?
For those who missed our previous Strangler Pattern article , here’s what you need to know about the Strangler pattern: It’s an approach to software development that places a legacy system behind a facade. As legacy applications and services are refactored, the facade reroutes users to those new versions. The facade is removed once modernization is complete.
While customer-facing changes may occur at the frontend, this approach can reduce risk during cloud migration, ensure legacy systems remain operational, and add new applications or services without compromising overall system health. The Strangler pattern enables the gradual transition to future-proof applications that can quickly and continuously adapt to future technological advancements.
3 Phases of Strangler Pattern Planning & Analysis
By the time you’re considering the Strangler pattern approach, you’ve already considered an application modernization strategy. Now, it’s time to dive deeper into specific monoliths to understand the infrastructure, including each application’s codebase and business logic, and identify optimal components to update. While time-consuming upfront, this level of detail can result in fewer mistakes down the line, saving both time and resources.
Generally, planning and analysis for implementing the Strangler pattern approach requires three broad phases. Let’s walk through each in detail.
1. Assessment Phase
During the assessment phase, application architects evaluate the existing system to identify components for the initial migration phase. This involves a thorough application modernization assessment of the legacy system, including:
- Architecture: Understand the legacy system’s components, modules, layers, and interactions to identify key areas for improvement.
- Functionalities: Get a full picture of existing capabilities to ensure essential features are seamlessly integrated into the new architecture.
- Dependencies: Take note of the dependencies that exist between components and modules within the application infrastructure, as well as external dependencies with other systems to minimize disruption.
- Limitations: Assess existing system limitations, such as technical debt, scalability issues, performance bottlenecks, and outdated technologies.
Once you’ve identified the components you need to replace or upgrade, the next step is to prioritize those initiatives. This requires you to assess the risks associated with each component and identify which resolutions will drive the greatest user and business impact. Here are some examples:
Technical Debt
Legacy systems often have a lot of inefficiencies, otherwise known as technical debt. This is one of the foremost reasons companies choose to modernize applications and, in particular, use the iterative Strangler pattern approach. Prioritizing areas with the most unused or unusable code can have a high impact on overall performance.
Cost Optimization
The fastest path to Strangler pattern ROI is identifying the applications that are consuming the most unproductive time and spend, whether for fixing bugs or adding new features, and migrating them first.
System Failure
Continuing with a legacy system, especially one in an increasingly degrading state, heightens the risk of system failure. Prioritizing components most likely to contribute to system failure in your cloud migration can significantly reduce this risk.
Application Complexity
Often, legacy systems are complex and poorly documented. Prioritizing the modernization of complex components can accelerate the simplification of your architecture and improve the likelihood of smooth tandem operation during the migration.
Operational Disruption
Broken workflows and outages severely disrupt business operations and hinder user satisfaction. Prioritizing components that could hinder business continuity can ensure efficient operations throughout the modernization process.
2. Strategy Development Phase
Once you’ve performed your assessment and identified high-impact actions to achieve your strategic goals, it’s time to flesh that out into a more developed, coherent application modernization strategy. This involves setting goals, establishing timelines, and identifying key stakeholders in the process.
The Strangler pattern is attractive to many developers not only because it enables a gradual, stable transition for long-term application modernization projects, but also because it’s flexible enough to support a number of IT strategies.
To align your approach with your goals, it’s important to understand the outcome you’re trying to drive by using the Strangler pattern. This can include:
- Legacy system modernization: The Strangler pattern is most often used to modernize outdated systems that are difficult to maintain, scale, or integrate.
- Incremental feature development: Developers can use the Strangler pattern approach to build and deploy new features without disrupting the existing system.
- Migration to microservices architecture: The gradual Strangler pattern approach can reduce the immediate complexity involved in breaking down a monolith into a microservices architecture.
- Refactoring and codebase improvement: The Strangler pattern allows organizations to refactor a complex codebase to improve maintainability and performance.
Clarify when you expect to reach key milestones in your application modernization process.
Then, determine the approach you need to take. In practice, developers may use the Strangler pattern to:
- Modernize applications that rely on outdated technologies
- Turn traditional, server-based applications into more dynamic, serverless solutions
- Transition enterprise-class databases—particularly those operating through complex, trigger-based mechanisms—to upgraded systems
3. Tooling and Infrastructure Requirements Phase
The final phase in setting up your Strangler pattern strategy for success involves building out the necessary tools and infrastructure, starting with these three.
API Gateway
Martin Fowler, who coined the Strangler pattern, notes the critical importance of “Event Interception” when using the approach. Your application must be able to reroute users—and API gateways, which are designed to intercept requests, make that possible.
Microservices Architecture
Microservices architecture enables the separation of large and complex applications into smaller, independent parts that carry their own responsibilities. Your organization must be prepared to establish an updated technology infrastructure that leverages this approach. CaaS+ by Capstone IT Solutions, our turnkey containerization solution, can provide the future-ready IT environment you need when adopting microservices or leveraging more complex architecture.
Cloud Platforms
Proactively identifying the right cloud platforms, where your microservices will eventually run, can enable the success of your Strangler pattern implementation. These platforms provide the scalability and flexibility your organization needs to achieve a future-proof IT system.
Final Thoughts on the Planning for Strangler Pattern Approach
Implementing the Strangler pattern shouldn’t be done haphazardly. The risks, goals, and tool and infrastructure needs associated with your modernization project must be thoroughly evaluated, enabling you to strategically prioritize the migration of different components. Your efforts can help you further mitigate issues in your cloud transformation journey. Working with application modernization experts who can provide advisory support will equip you with the processes and resources you need to ensure a seamless, effective transition.
Stay tuned for the next article in our series, which will dive into the beginning stages of Strangler pattern implementation.