custom health check

ShuttingDownHealthCheck.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Hosting;
+
+namespace blog_zero_downtime_with_health_checks
+{
+    public class ShuttingDownHealthCheck : IHealthCheck
+    {
+        private HealthStatus _status = HealthStatus.Healthy;
+
+        public ShuttingDownHealthCheck(IHostApplicationLifetime appLifetime)
+        {
+            appLifetime.ApplicationStopping.Register(() =>
+            {
+                Console.WriteLine("Shutting down");
+                _status = HealthStatus.Unhealthy;
+            });
+        }
+
+        public Task<HealthCheckResult> CheckHealthAsync(
+            HealthCheckContext context,
+            CancellationToken cancellationToken = default)
+        {
+            var result = new HealthCheckResult(_status);
+            return Task.FromResult(result);
+        }
+    }
+}

Startup.cs

@@ -16,7 +16,10 @@ public class Startup
         // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
         public void ConfigureServices(IServiceCollection services)
         {
-            services.AddHealthChecks();
+            services.AddSingleton<ShuttingDownHealthCheck>();
+
+            services.AddHealthChecks()
+                .AddCheck<ShuttingDownHealthCheck>("shutting_down");
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.