Consume PosixSignal in Hosting.Systemd's SystemdLifetime

src/libraries/Microsoft.Extensions.Hosting.Systemd/Directory.Build.props

@@ -2,5 +2,6 @@
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
     <PackageTags>hosting</PackageTags>
+    <IncludePlatformAttributes>true</IncludePlatformAttributes>
   </PropertyGroup>
 </Project>

src/libraries/Microsoft.Extensions.Hosting.Systemd/Microsoft.Extensions.Hosting.Systemd.sln

@@ -71,9 +71,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Hostin
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Hosting", "..\Microsoft.Extensions.Hosting\src\Microsoft.Extensions.Hosting.csproj", "{AFC1BDAA-7E40-4118-BB80-F8057752A600}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Logging.Generators", "..\Microsoft.Extensions.Logging.Abstractions\gen\Microsoft.Extensions.Logging.Generators.Roslyn3.11.csproj", "{5F69DAFF-F4BC-4E29-A4FA-E96A4D55EC2D}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Logging.Generators.Roslyn3.11", "..\Microsoft.Extensions.Logging.Abstractions\gen\Microsoft.Extensions.Logging.Generators.Roslyn3.11.csproj", "{5F69DAFF-F4BC-4E29-A4FA-E96A4D55EC2D}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Logging.Generators", "..\Microsoft.Extensions.Logging.Abstractions\gen\Microsoft.Extensions.Logging.Generators.Roslyn4.0.csproj", "{0D1BFEB4-CEF6-4319-9212-E3E7840B287A}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Logging.Generators.Roslyn4.0", "..\Microsoft.Extensions.Logging.Abstractions\gen\Microsoft.Extensions.Logging.Generators.Roslyn4.0.csproj", "{0D1BFEB4-CEF6-4319-9212-E3E7840B287A}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Extensions.Logging.Abstractions", "..\Microsoft.Extensions.Logging.Abstractions\ref\Microsoft.Extensions.Logging.Abstractions.csproj", "{860B845B-929F-4442-AED1-1F4186DBF497}"
 EndProject
@@ -137,9 +137,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Encodings.Web",
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Encodings.Web", "..\System.Text.Encodings.Web\src\System.Text.Encodings.Web.csproj", "{47A3CDB0-8252-4536-B61F-C2E10F6EC2B9}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Json.SourceGeneration", "..\System.Text.Json\gen\System.Text.Json.SourceGeneration.Roslyn3.11.csproj", "{5C6A1B61-B02B-46AA-8AD5-B8F61EE57453}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Json.SourceGeneration.Roslyn3.11", "..\System.Text.Json\gen\System.Text.Json.SourceGeneration.Roslyn3.11.csproj", "{5C6A1B61-B02B-46AA-8AD5-B8F61EE57453}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Json.SourceGeneration", "..\System.Text.Json\gen\System.Text.Json.SourceGeneration.Roslyn4.0.csproj", "{771CB4BB-4237-444E-82CE-C81A4979D89F}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Json.SourceGeneration.Roslyn4.0", "..\System.Text.Json\gen\System.Text.Json.SourceGeneration.Roslyn4.0.csproj", "{771CB4BB-4237-444E-82CE-C81A4979D89F}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Text.Json", "..\System.Text.Json\ref\System.Text.Json.csproj", "{AA2CD494-414F-42BF-9C68-7822DEB09255}"
 EndProject

src/libraries/Microsoft.Extensions.Hosting.Systemd/ref/Microsoft.Extensions.Hosting.Systemd.cs

@@ -31,13 +31,19 @@ public static partial class SystemdHelpers
     {
         public static bool IsSystemdService() { throw null; }
     }
+    [System.Runtime.Versioning.UnsupportedOSPlatform("android")]
+    [System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
+    [System.Runtime.Versioning.UnsupportedOSPlatform("ios")]
+    [System.Runtime.Versioning.UnsupportedOSPlatform("maccatalyst")]
+    [System.Runtime.Versioning.UnsupportedOSPlatform("tvos")]
     public partial class SystemdLifetime : Microsoft.Extensions.Hosting.IHostLifetime, System.IDisposable
     {
         public SystemdLifetime(Microsoft.Extensions.Hosting.IHostEnvironment environment, Microsoft.Extensions.Hosting.IHostApplicationLifetime applicationLifetime, Microsoft.Extensions.Hosting.Systemd.ISystemdNotifier systemdNotifier, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory) { }
         public void Dispose() { }
         public System.Threading.Tasks.Task StopAsync(System.Threading.CancellationToken cancellationToken) { throw null; }
         public System.Threading.Tasks.Task WaitForStartAsync(System.Threading.CancellationToken cancellationToken) { throw null; }
     }
+    [System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
     public partial class SystemdNotifier : Microsoft.Extensions.Hosting.Systemd.ISystemdNotifier
     {
         public SystemdNotifier() { }

src/libraries/Microsoft.Extensions.Hosting.Systemd/ref/Microsoft.Extensions.Hosting.Systemd.csproj

@@ -1,12 +1,20 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.1</TargetFrameworks>
     <EnableDefaultItems>true</EnableDefaultItems>
   </PropertyGroup>
 
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Hosting\ref\Microsoft.Extensions.Hosting.csproj" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <Reference Include="netstandard" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' and '$(TargetFramework)' != '$(NetCoreAppCurrent)'">
+    <Reference Include="System.Runtime" />
+  </ItemGroup>
+
 </Project>

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/Microsoft.Extensions.Hosting.Systemd.csproj

@@ -1,11 +1,21 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.1</TargetFrameworks>
     <EnableDefaultItems>true</EnableDefaultItems>
     <PackageDescription>.NET hosting infrastructure for Systemd Services.</PackageDescription>
+    <!-- Use targeting pack references instead of granular ones in the project file. -->
+    <DisableImplicitAssemblyReferences>false</DisableImplicitAssemblyReferences>
   </PropertyGroup>
 
+  <ItemGroup Condition="!$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0'))">
+    <Compile Remove="SystemdLifetime.netcoreapp.cs" />
+  </ItemGroup>
+
+  <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0'))">
+    <Compile Remove="SystemdLifetime.netstandard.cs" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Hosting\src\Microsoft.Extensions.Hosting.csproj" />
   </ItemGroup>

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdHostBuilderExtensions.cs

@@ -40,8 +40,11 @@ public static IHostBuilder UseSystemd(this IHostBuilder hostBuilder)
                         options.FormatterName = ConsoleFormatterNames.Systemd;
                     });
 
+                    // IsSystemdService() will never return true for android/browser/iOS/tvOS
+#pragma warning disable CA1416 // Validate platform compatibility
                     services.AddSingleton<ISystemdNotifier, SystemdNotifier>();
                     services.AddSingleton<IHostLifetime, SystemdLifetime>();
+#pragma warning restore CA1416 // Validate platform compatibility
                 });
             }
             return hostBuilder;

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdLifetime.cs

@@ -2,15 +2,20 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.Extensions.Hosting.Systemd
 {
-    public class SystemdLifetime : IHostLifetime, IDisposable
+    [UnsupportedOSPlatform("android")]
+    [UnsupportedOSPlatform("browser")]
+    [UnsupportedOSPlatform("ios")]
+    [UnsupportedOSPlatform("maccatalyst")]
+    [UnsupportedOSPlatform("tvos")]
+    public partial class SystemdLifetime : IHostLifetime, IDisposable
     {
-        private readonly ManualResetEvent _shutdownBlock = new ManualResetEvent(false);
         private CancellationTokenRegistration _applicationStartedRegistration;
         private CancellationTokenRegistration _applicationStoppingRegistration;
 
@@ -45,12 +50,13 @@ public Task WaitForStartAsync(CancellationToken cancellationToken)
             },
             this);
 
-            // systemd sends SIGTERM to stop the service.
-            AppDomain.CurrentDomain.ProcessExit += OnProcessExit;
+            RegisterShutdownHandlers();
 
             return Task.CompletedTask;
         }
 
+        private partial void RegisterShutdownHandlers();
+
         private void OnApplicationStarted()
         {
             Logger.LogInformation("Application started. Hosting environment: {EnvironmentName}; Content root path: {ContentRoot}",
@@ -66,25 +72,14 @@ private void OnApplicationStopping()
             SystemdNotifier.Notify(ServiceState.Stopping);
         }
 
-        private void OnProcessExit(object sender, EventArgs e)
-        {
-            ApplicationLifetime.StopApplication();
-
-            _shutdownBlock.WaitOne();
-
-            // On Linux if the shutdown is triggered by SIGTERM then that's signaled with the 143 exit code.
-            // Suppress that since we shut down gracefully. https://github.com/dotnet/aspnetcore/issues/6526
-            System.Environment.ExitCode = 0;
-        }
-
         public void Dispose()
         {
-            _shutdownBlock.Set();
-
-            AppDomain.CurrentDomain.ProcessExit -= OnProcessExit;
+            UnregisterShutdownHandlers();
 
             _applicationStartedRegistration.Dispose();
             _applicationStoppingRegistration.Dispose();
         }
+
+        private partial void UnregisterShutdownHandlers();
     }
 }

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdLifetime.netcoreapp.cs

@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Extensions.Hosting.Systemd
+{
+    public partial class SystemdLifetime
+    {
+        private PosixSignalRegistration _sigTermRegistration;
+
+        private partial void RegisterShutdownHandlers()
+        {
+            // systemd only sends SIGTERM to the service process, so we only listen for that signal.
+            // Other signals (ex. SIGINT/SIGQUIT) will be handled by the default .NET runtime signal handler
+            // and won't cause a graceful shutdown of the systemd service.
+            _sigTermRegistration = PosixSignalRegistration.Create(PosixSignal.SIGTERM, HandlePosixSignal);
+        }
+
+        private void HandlePosixSignal(PosixSignalContext context)
+        {
+            Debug.Assert(context.Signal == PosixSignal.SIGTERM);
+
+            context.Cancel = true;
+            ApplicationLifetime.StopApplication();
+        }
+
+        private partial void UnregisterShutdownHandlers()
+        {
+            _sigTermRegistration?.Dispose();
+        }
+    }
+}

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdLifetime.netstandard.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Threading;
+
+namespace Microsoft.Extensions.Hosting.Systemd
+{
+    public partial class SystemdLifetime
+    {
+        private readonly ManualResetEvent _shutdownBlock = new ManualResetEvent(false);
+
+        private partial void RegisterShutdownHandlers()
+        {
+            // systemd sends SIGTERM to stop the service.
+            AppDomain.CurrentDomain.ProcessExit += OnProcessExit;
+        }
+
+        private void OnProcessExit(object sender, EventArgs e)
+        {
+            ApplicationLifetime.StopApplication();
+
+            _shutdownBlock.WaitOne();
+
+            // On Linux if the shutdown is triggered by SIGTERM then that's signaled with the 143 exit code.
+            // Suppress that since we shut down gracefully. https://github.com/dotnet/aspnetcore/issues/6526
+            System.Environment.ExitCode = 0;
+        }
+
+        private partial void UnregisterShutdownHandlers()
+        {
+            _shutdownBlock.Set();
+
+            AppDomain.CurrentDomain.ProcessExit -= OnProcessExit;
+        }
+    }
+}

src/libraries/Microsoft.Extensions.Hosting.Systemd/src/SystemdNotifier.cs

@@ -2,11 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using System.IO;
 using System.Net.Sockets;
+using System.Runtime.Versioning;
 
 namespace Microsoft.Extensions.Hosting.Systemd
 {
+    [UnsupportedOSPlatform("browser")]
     public class SystemdNotifier : ISystemdNotifier
     {
         private const string NOTIFY_SOCKET = "NOTIFY_SOCKET";
@@ -57,7 +58,11 @@ private static string GetNotifySocketPath()
             // Support abstract socket paths.
             if (socketPath[0] == '@')
             {
-                socketPath = "\0" + socketPath.Substring(1);
+                socketPath = string.Create(socketPath.Length, socketPath, (buffer, state) =>
+                {
+                    buffer[0] = '\0';
+                    state.AsSpan(1).CopyTo(buffer.Slice(1));
+                });
             }
 
             return socketPath;