How to do gracefully shutdown on dotnet with docker?

Question

Is there a way to gracefully shut-down a DOTNET CORE application which is running in DOCKER? If yes, which event I should listen?

All I want is upon cancellation request I would like to pass my cancellation token/s to current methods and postpone the shut-down while they are working.

Looking for a sample code, reference link etc. which are relevant to dotnet core and not generic info

UPDATE This question is not a duplicate of docker container exits immediately even with Console.ReadLine() in a .net core console application because I'm not having an immediate exit issue. I need to tap into event something like Windows.SystemsEvents.SessionEnding and relying on Console.CancelKeyPress and/or implementing WebHostBuilder() doesn't fit the bill.

Answer 1

In .NET Core 2.0, you can use the AppDomain.CurrentDomain.ProcessExit event, which works fine on Linux in Docker. AssemblyLoadContext.Default.Unloading probably works as well, even before .NET Core 2.0.

Answer 2

System.Console has an event called CancelKeyPress. I believe this is fired when a sigint event is passed into dotnet.

System.Console.CancelKeyPress += (s,e) => { /* do something here */};

Answer 3

Using 2.0.0-preview2-006497 I did some testing, and now the AssemblyLoadContext.Default.Unloading is fired when Docker sends a SIGTERM/SIGINT to the container.

Example code looks like:

System.Runtime.Loader.AssemblyLoadContext.Default.Unloading += ctx =>
{
    // code here...
};

See also this issue for some details: https://github.com/aspnet/Hosting/issues/870

Answer 4

If your container is running in Linux then Loader.AssemblyLoadContext.Default.Unloading works since it can trap the SIGTERM signal, however Windows do not have the equivalent mechanism for this(dotnet issue). Here's an answer to handle shutdown notification in Windows by using SetConsoleCtrlHandler originally from gist

namespace Routeguide
{
    using System;
    using System.Threading;
    ...

    class Program
    {
        [DllImport("Kernel32")]
        internal static extern bool SetConsoleCtrlHandler(HandlerRoutine handler, bool Add);

        internal delegate bool HandlerRoutine(CtrlTypes ctrlType);

        internal enum CtrlTypes
        {
            CTRL_C_EVENT = 0,
            CTRL_BREAK_EVENT,
            CTRL_CLOSE_EVENT,
            CTRL_LOGOFF_EVENT = 5,
            CTRL_SHUTDOWN_EVENT
        }

        static void Main(string[] args)
        {
            // do the server starting code
            Start();
            ....

            var shutdown = new ManualResetEvent(false);
            var complete = new ManualResetEventSlim();
            var hr = new HandlerRoutine(type =>
            {
                Log.Logger.Information($"ConsoleCtrlHandler got signal: {type}");

                shutdown.Set();
                complete.Wait();

                return false;
            });
            SetConsoleCtrlHandler(hr, true);

            Console.WriteLine("Waiting on handler to trigger...");

            shutdown.WaitOne();

            Console.WriteLine("Stopping server...");

            // do the server stopping code
            Stop();

            complete.Set();
            GC.KeepAlive(hr);
        }
    }
}