Strangler pattern

As explained in Google Anthos in Action

The strangler fig pattern incrementally replaces parts of a legacy system with new implementations until the legacy system is reduced or removed.

The strangler pattern incrementally replaces a legacy application with new implementations, commonly while refactoring toward microservices. Each extracted capability delivers value in a production release, narrows deployment scope, and reduces modernization risk compared with rewriting the entire application first. section 16.2.1

Apply the pattern by:

• Selecting features that support the application and are easy to decouple. section 16.2.1
• Evaluating candidates across business process, design and development, operations, and people and teams. section 16.2.1
• Extracting the chosen logic, integrating it with the existing application, and releasing the change incrementally. section 16.2.1
• Considering centralized authentication and authorization as a possible early extraction target. section 16.2.1

Figure 16.2 Modernizing a Java application

Use the modernization diagram to visualize how a Java application can move incrementally away from its legacy design. section 16.2.1

How Google Anthos in Action covers it

How deep it goes

Explains the rationale, candidate-selection heuristic, and evaluation dimensions, but does not detail routing or integration mechanics.

Examples

Uses centralized authentication and authorization as an example of an easily decoupled feature.

What you can do after

Apply incremental extraction to reduce modernization risk and deliver architectural improvements through successive production releases.

How it connects

Connects legacy applications, microservices architecture, service boundaries, automated testing, and automated deployment.

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Also explained in

• 

  liveBookmanning.com
  Architecture Modernization: Socio-technical alignment of software, strategy, and structureThe strangler fig pattern is a migration pattern that gradually replaces an existing system by routing increasing responsibility to a new system until the old system is no longer needed.
• 

  liveBookmanning.com
  ASP.NET Core in Action, 3eThe strangler fig pattern is an incremental modernization pattern in which new functionality gradually replaces parts of an existing system until the legacy system can be retired.
• 

  liveBookmanning.com
  Kafka for ArchitectsThe strangler fig pattern is an incremental replacement approach in which a new implementation gradually takes over functionality from a legacy system.

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Related concepts

• legacy systemaddresses · A legacy system is an existing software or computing system that remains in use or must be maintained despite older technologies, designs, or constraints that can complicate change.
• feature flaguses · A feature flag is a configuration control that conditionally enables, disables, or selects a software feature or behavior.
• microservice architectureused by · Microservice architecture is a software architectural style that organizes an application as independently deployable services with focused responsibilities that communicate through defined interfaces.
• YAGNI principleimplements · The YAGNI principle is a software design discipline of avoiding functionality or structure until a concrete need for it arises.

This explainer was generated by Manning's knowledge graph from the text of Google Anthos in Action. The section links point to the parts of the book it draws on.