Graceful SIGTERM Shutdown & `IHostApplicationLifetime`

1Concept

When Kubernetes scales down or restarts pods, it sends a `SIGTERM` signal. ASP.NET Core gives the application a grace period (default 30s) to finish in-flight HTTP requests and flush message buffers before `SIGKILL`.

2Architecture Diagram

Kubernetes sends SIGTERM
       │
[ IHostApplicationLifetime.ApplicationStopping Triggered ]
  ├── Kestrel stops accepting new HTTP connections
  ├── In-flight HTTP requests complete cleanly
  └── Channels & Background workers flush buffers to disk
       │
[ Process Exits Code 0 (Zero Dropped User Transactions!) ]

3Code Example

using System;

public class GracefulShutdownConceptDemo
{
    public static void Main()
    {
        Console.WriteLine("Graceful shutdown registration:");
        Console.WriteLine("app.Lifetime.ApplicationStopping.Register(() => {");
        Console.WriteLine("    Console.WriteLine("Flushing message queues before container termination...");");
        Console.WriteLine("});");
    }
}

4Expected Output

Graceful shutdown registration:
app.Lifetime.ApplicationStopping.Register(() => {
    Console.WriteLine("Flushing message queues before container termination...");
});

5Key Takeaways

• ✓Register teardown tasks on `IHostApplicationLifetime.ApplicationStopping`.
• ✓Configure Kubernetes `terminationGracePeriodSeconds: 60` for long batch operations.
• ✓Ensures zero dropped HTTP requests during rolling cluster deployments.