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Details in Strangler Fig pattern - Azure Architecture Center | Microsoft Learn

Problem

  • Need to incrementally migrate a legacy system to a new service in the cloud and so, gradually.

  • Run 2 separate systems or versions of an app means that clients have to know where particular features are located.

  • Need to minimize the risk from the migration of app and data.

Solution

  • Create a façade that intercepts requests going to the backend legacy system. The façade routes these requests either to the legacy application or the new services.

...

Strangler In Practice

  • Option A : Using Azure Application Gateway.

    • The facade is a reverse proxy and not cesseraly a forward proxy : we can use Azure Application Gateway or Azure Service Fabric Reverse Proxy.

    • We need to have multiple instances of the same service or multiple versions of the same service if we wish to use Azure Application Gateway (Gateway Routing Pattern)

  • Option B : Creating the strangler Fig in code.

    • The other option would be in the code only : we set up our routes, pointing to 2 different clusters (being our apps - modern and legacy).

      1. Create to code related to the read of the routes

      Code Block
      languagec#
      var builder = WebApplication.CreateBuilder(args);
builder.Services.AddReverseProxy()
    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));
var app = builder.Build();
app.MapReverseProxy();
app.Run();

...