Cloud-Native Configuration

Video

Overriding Configuration At Runtime

ASP.NETCore provides a machanism for overriding the appsettings.json at runtime. This provides a simple way to "inject" our runtime configuration from a Kubernetes/OpenShift ConfigMap or Secret.

1. Modify the Program.cs to add an optional configuration file to be loaded

   public static IHostBuilder CreateHostBuilder(string[] args) =>
      Host.CreateDefaultBuilder(args)
            .UseSerilog()
            .ConfigureAppConfiguration((hostingContext, config) =>
            {
               config.AddJsonFile("/tmp/config/runtimesettings.json", optional: true, reloadOnChange: false);
            })
            // SNIP - Remaining Host Builder

2. Now, when we deploy our application on OpenShift, it will look for a file in /tmp/config called runtimesettings.json and those settings will override any settings in our appsettings.json.
3. We can define our Deployment or DeploymentConfig such that we mount a ConfigMap or Secret containing that JSON configuration in that location