LifetimeEventsHostedService.cs

using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace Lybecker.K8sFriendlyAspNetCore
{
    internal class LifetimeEventsHostedService : IHostedService
    {
        private readonly ILogger _logger;
        private readonly IApplicationLifetime _appLifetime;

        public LifetimeEventsHostedService(
            ILogger<LifetimeEventsHostedService> logger, 
            IApplicationLifetime appLifetime)
        {
            _logger = logger;
            _appLifetime = appLifetime;
        }

        public Task StartAsync(CancellationToken cancellationToken)
        {
            _appLifetime.ApplicationStarted.Register(OnStarted);
            _appLifetime.ApplicationStopping.Register(OnStopping);
            _appLifetime.ApplicationStopped.Register(OnStopped);

            return Task.CompletedTask;
        }

        public Task StopAsync(CancellationToken cancellationToken)
        {
            return Task.CompletedTask;
        }

        private void OnStarted()
        {
            _logger.LogInformation("OnStarted has been called.");

            // Perform post-startup activities here
        }

        private void OnStopping()
        {
            _logger.LogInformation("OnStopping has been called. Start cleanup for gracefull shutdown.");

            // simulate long shutdown
            for (int i = 1; i <= 10; i++)
            {
                System.Threading.Thread.Sleep(1000);
                _logger.LogInformation($"Cleaning up...  processing for {i} secs");
            }
        }

        private void OnStopped()
        {
            _logger.LogInformation("OnStopped has been called.");

            // Perform post-stopped activities here
        }
    }
}