Strangler Pattern - Simplified

The Strangler Pattern is a software development approach to replace a legacy system with a new one incrementally. It's named after the Strangler Fig plant that gradually grows on and replaces other trees. This method allows you to gradually replace parts of an existing system with a new one, reducing the risks associated with a complete system overhaul.

To understand the Strangler Pattern, consider it as gradually renovating a large, old house room by room while still living in it. Here's a simplified step-by-step explanation:

• Understanding the Whole House (Legacy System): Before you begin, you need a good understanding of the current state of your house. In the same way, you must understand your legacy system's functionalities, connections, strengths, and weaknesses.

• Identifying the First Room (Strangler Point): You can't renovate the whole house simultaneously, so you start with one room. In the same way, you identify parts of the legacy system (called strangler points) that can be independently developed and replaced. This could be a feature, module, or service within the system.

• Designing the New Room (New Module): Once you've identified the first room to renovate, you design the new version of it. Similarly, you develop a new version of the module or feature using modern technology.

• Building Connections (Creating Interfaces): During the renovation, you'll need a way to move between the old and new rooms. In the software world, this is done by creating interfaces which allow the new and old parts to interact seamlessly.

• Renovating the Room (Replacing Module): Now, you renovate the identified room according to the new design. As you said, I replaced the old software module with the new one. The new module now takes on the responsibilities of the old one.

• Moving Into the New Room (Transition): Once the renovation is complete, you start using the new room and stop using the old one. Similarly, users start using the new module and stop using the replaced module.

• Repeating the Process: Now, you move to the next room and repeat the process until the entire house is renovated. In the same way, you progressively replace all the legacy system parts until the whole system is modernised.

This step-by-step approach allows a less disruptive, more controlled transition from the legacy system to the new one. It also spreads the cost over a longer period, making it easier to manage the budget.

I hope you enjoyed reading the simplified version of the Strangler Pattern. Please share your thoughts. You can contact me if you need a consultancy to implement a new system with business as usual. I can assure you of a successful transition.

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