How to write a linux daemon with .Net Core

Question

I could just write a long-running CLI app and run it, but I\'m assuming it wouldn\'t comply to all the expectations one would have of a standards-compliant linux daemon (respond

Answer 1

I toyed with an idea similar to how .net core web host waits for shutdown in console applications. I was reviewing it on GitHub and was able to extract the gist of how they performed the Run

https://github.com/aspnet/Hosting/blob/15008b0b7fcb54235a9de3ab844c066aaf42ea44/src/Microsoft.AspNetCore.Hosting/WebHostExtensions.cs#L86

public static class ConsoleHost {
    /// 

    /// Block the calling thread until shutdown is triggered via Ctrl+C or SIGTERM.
    /// 
    public static void WaitForShutdown() {
        WaitForShutdownAsync().GetAwaiter().GetResult();
    }


    /// 

    /// Runs an application and block the calling thread until host shutdown.
    /// 
    /// The  to run.
    public static void Wait() {
        WaitAsync().GetAwaiter().GetResult();
    }

    /// 

    /// Runs an application and returns a Task that only completes when the token is triggered or shutdown is triggered.
    /// 
    /// The  to run.
    /// The token to trigger shutdown.
    public static async Task WaitAsync(CancellationToken token = default(CancellationToken)) {
        //Wait for the token shutdown if it can be cancelled
        if (token.CanBeCanceled) {
            await WaitAsync(token, shutdownMessage: null);
            return;
        }
        //If token cannot be cancelled, attach Ctrl+C and SIGTERN shutdown
        var done = new ManualResetEventSlim(false);
        using (var cts = new CancellationTokenSource()) {
            AttachCtrlcSigtermShutdown(cts, done, shutdownMessage: "Application is shutting down...");
            await WaitAsync(cts.Token, "Application running. Press Ctrl+C to shut down.");
            done.Set();
        }
    }

    /// 

    /// Returns a Task that completes when shutdown is triggered via the given token, Ctrl+C or SIGTERM.
    /// 
    /// The token to trigger shutdown.
    public static async Task WaitForShutdownAsync(CancellationToken token = default (CancellationToken)) {
        var done = new ManualResetEventSlim(false);
        using (var cts = CancellationTokenSource.CreateLinkedTokenSource(token)) {
            AttachCtrlcSigtermShutdown(cts, done, shutdownMessage: string.Empty);
            await WaitForTokenShutdownAsync(cts.Token);
            done.Set();
        }
    }

    private static async Task WaitAsync(CancellationToken token, string shutdownMessage) {
        if (!string.IsNullOrEmpty(shutdownMessage)) {
            Console.WriteLine(shutdownMessage);
        }
        await WaitForTokenShutdownAsync(token);
    }


    private static void AttachCtrlcSigtermShutdown(CancellationTokenSource cts, ManualResetEventSlim resetEvent, string shutdownMessage) {
        Action ShutDown = () => {
            if (!cts.IsCancellationRequested) {
                if (!string.IsNullOrWhiteSpace(shutdownMessage)) {
                    Console.WriteLine(shutdownMessage);
                }
                try {
                    cts.Cancel();
                } catch (ObjectDisposedException) { }
            }
            //Wait on the given reset event
            resetEvent.Wait();
        };

        AppDomain.CurrentDomain.ProcessExit += delegate { ShutDown(); };
        Console.CancelKeyPress += (sender, eventArgs) => {
            ShutDown();
            //Don't terminate the process immediately, wait for the Main thread to exit gracefully.
            eventArgs.Cancel = true;
        };
    }

    private static async Task WaitForTokenShutdownAsync(CancellationToken token) {
        var waitForStop = new TaskCompletionSource