Watch for parent process exit (#333)

* Add dependent process watcher service

Adds an IHostedService that will watch one or more dependent processes and call IHostApplicationLifetime.StopApplication when a dependent process exits

* Use dependent process watcher in example hosts and template

Registers the dependent process watcher hosted service if the `AppStoreConnect:Adapter:Host:ParentPid` configuration setting value is greater than zero.

examples/ExampleHostedAdapter/Program.cs

@@ -16,6 +16,12 @@
 builder.Configuration
     .AddJsonFile(Constants.AdapterSettingsFilePath, false, true);
 
+// Parent PID. If specified, we will gracefully shut down if the parent process exits.
+var pid = builder.Configuration.GetValue<int>("AppStoreConnect:Adapter:Host:ParentPid");
+if (pid > 0) {
+    builder.Services.AddDependentProcessWatcher(pid);
+}
+
 // Host instance ID.
 var instanceId = builder.Configuration.GetValue<string>("AppStoreConnect:Adapter:Host:InstanceId");
 if (string.IsNullOrWhiteSpace(instanceId)) {

examples/MinimalApiExample/Program.cs

@@ -11,6 +11,12 @@
 
 var builder = WebApplication.CreateBuilder(args);
 
+// Parent PID. If specified, we will gracefully shut down if the parent process exits.
+var pid = builder.Configuration.GetValue<int>("AppStoreConnect:Adapter:Host:ParentPid");
+if (pid > 0) {
+    builder.Services.AddDependentProcessWatcher(pid);
+}
+
 builder.Services
     .AddLocalization()
     .AddProblemDetails();

src/DataCore.Adapter.AspNetCore.Common/Configuration/CommonAdapterConfigurationExtensions.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Numerics;
 using System.Reflection;
 
 using DataCore.Adapter;
@@ -63,7 +62,7 @@ public static IAdapterConfigurationBuilder AddDataCoreAdapterAspNetCoreServices(
         ///   <paramref name="hostInfo"/> is <see langword="null"/>.
         /// </exception>
         public static IAdapterConfigurationBuilder AddHostInfo(
-            this IAdapterConfigurationBuilder builder, 
+            this IAdapterConfigurationBuilder builder,
             HostInfo hostInfo
         ) {
             if (builder == null) {
@@ -310,7 +309,7 @@ public static IAdapterConfigurationBuilder AddHostInfo(this IAdapterConfiguratio
                     .WithName(entryAssembly?.GetName()?.FullName)
                     .WithVersion(entryAssembly?.GetInformationalVersion())
                     .WithVendor(sp.GetService<VendorInfo>() ?? entryAssembly?.GetCustomAttribute<VendorInfoAttribute>()?.CreateVendorInfo());
-                
+
                 AddOperatingSystemHostInfoProperty(hostInfoBuilder);
                 AddContainerHostInfoProperty(hostInfoBuilder);
 
@@ -507,6 +506,70 @@ public static IAdapterConfigurationBuilder AddDefaultAspNetCoreServices(this IAd
             return builder;
         }
 
+
+        /// <summary>
+        /// Registers an <see cref="IHostedService"/> that will request a graceful application 
+        /// shutdown when any of the specified processes exit.
+        /// </summary>
+        /// <param name="services">
+        ///   The <see cref="IServiceCollection"/>.
+        /// </param>
+        /// <param name="pid">
+        ///   The PID of the first process to watch.
+        /// </param>
+        /// <param name="additionalPids">
+        ///   The PID of any additional processes to watch.
+        /// </param>
+        /// <returns>
+        ///   The <see cref="IServiceCollection"/>.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        ///   <paramref name="services"/> is <see langword="null"/>.
+        /// </exception>
+        /// <remarks>
+        ///   This method is intended to allow adapter host applications that are started by an 
+        ///   external application such as App Store Connect to exit if the external application 
+        ///   exits without stopping the adapter host.
+        /// </remarks>
+        public static IServiceCollection AddDependentProcessWatcher(this IServiceCollection services, int pid, params int[] additionalPids) => AddDependentProcessWatcher(services, new[] { pid }.Concat(additionalPids));
+
+
+        /// <summary>
+        /// Registers an <see cref="IHostedService"/> that will request a graceful application 
+        /// shutdown when any of the specified processes exit.
+        /// </summary>
+        /// <param name="services">
+        ///   The <see cref="IServiceCollection"/>.
+        /// </param>
+        /// <param name="pids">
+        ///   The PIDs of the processes to watch.
+        /// </param>
+        /// <returns>
+        ///   The <see cref="IServiceCollection"/>.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        ///   <paramref name="services"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ArgumentNullException">
+        ///   <paramref name="pids"/> is <see langword="null"/>.
+        /// </exception>
+        /// <remarks>
+        ///   This method is intended to allow adapter host applications that are started by an 
+        ///   external application such as App Store Connect to exit if the external application 
+        ///   exits without stopping the adapter host.
+        /// </remarks>
+        public static IServiceCollection AddDependentProcessWatcher(this IServiceCollection services, IEnumerable<int> pids) {
+            if (services == null) {
+                throw new ArgumentNullException(nameof(services));
+            }
+            if (pids == null) {
+                throw new ArgumentNullException(nameof(pids));
+            }
+
+            services.AddHostedService(sp => ActivatorUtilities.CreateInstance<DependentProcessWatcher>(sp, pids));
+            return services;
+        }
+
     }
 
 }

src/DataCore.Adapter.AspNetCore.Common/Internal/DependentProcessWatcher.cs

@@ -0,0 +1,100 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace DataCore.Adapter.AspNetCore.Internal {
+
+    /// <summary>
+    /// <see cref="IHostedService"/> that watches a set of dependent processes and will request 
+    /// that the application gracefully exits if any of the dependent processes exit.
+    /// </summary>
+    internal sealed partial class DependentProcessWatcher : BackgroundService {
+
+        /// <summary>
+        /// The <see cref="IHostApplicationLifetime"/> that is used to request graceful shutdown 
+        /// if required.
+        /// </summary>
+        private readonly IHostApplicationLifetime _hostApplicationLifetime;
+
+        /// <summary>
+        /// Logging.
+        /// </summary>
+        private readonly ILogger<DependentProcessWatcher> _logger;
+
+        /// <summary>
+        /// The process IDs to watch.
+        /// </summary>
+        private readonly int[] _pids;
+
+
+        /// <summary>
+        /// Creates a new <see cref="DependentProcessWatcher"/> instance.
+        /// </summary>
+        /// <param name="pids">
+        ///   The process IDs to watch. Note that specifying a PID that does not exist will result 
+        ///   in immediate shutdown of the host application when <see cref="ExecuteAsync"/> is called.
+        /// </param>
+        /// <param name="hostApplicationLifetime">
+        ///   The <see cref="IHostApplicationLifetime"/>.
+        /// </param>
+        /// <param name="logger">
+        ///   The <see cref="ILogger"/>.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        ///   <paramref name="pids"/> is <see langword="null"/>.
+        /// </exception>
+        /// <remarks>
+        ///   Specifying a PID that does not exist will result in immediate shutdown of the host 
+        ///   application when <see cref="ExecuteAsync"/> is called.
+        /// </remarks>
+        public DependentProcessWatcher(IEnumerable<int> pids, IHostApplicationLifetime hostApplicationLifetime, ILogger<DependentProcessWatcher> logger) {
+            _logger = logger;
+            _hostApplicationLifetime = hostApplicationLifetime;
+            _pids = pids?.ToArray() ?? throw new ArgumentNullException(nameof(pids));
+        }
+
+
+        /// <inheritdoc/>
+        protected override Task ExecuteAsync(CancellationToken stoppingToken) {
+            foreach (var pid in _pids) {
+                var process = Process.GetProcessById(pid);
+                if (process == null) {
+                    LogProcessNotFound(pid);
+                    _hostApplicationLifetime.StopApplication();
+                    break;
+                }
+
+                var name = process.ProcessName;
+
+                LogWatchingProcess(pid, name);
+
+                process.EnableRaisingEvents = true;
+                process.Exited += (sender, args) => { 
+                    if (!stoppingToken.IsCancellationRequested) {
+                        LogProcessExited(pid, name);
+                        _hostApplicationLifetime.StopApplication();
+                    }
+                };
+            }
+
+            return Task.CompletedTask;
+        }
+
+
+        [LoggerMessage(0, LogLevel.Information, "Watching dependent process '{name}' (PID: {pid}).")]
+        partial void LogWatchingProcess(int pid, string name);
+
+        [LoggerMessage(1, LogLevel.Warning, "Dependent process '{name}' (PID: {pid}) has exited.")]
+        partial void LogProcessExited(int pid, string name);
+
+        [LoggerMessage(2, LogLevel.Warning, "Dependent process {pid} does not exist or has already exited.")]
+        partial void LogProcessNotFound(int pid);
+
+    }
+}

src/DataCore.Adapter.AspNetCore.Common/PublicAPI.Unshipped.txt

@@ -1,4 +1,6 @@
 #nullable enable
+static Microsoft.Extensions.DependencyInjection.CommonAdapterConfigurationExtensions.AddDependentProcessWatcher(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, int pid, params int[]! additionalPids) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
+static Microsoft.Extensions.DependencyInjection.CommonAdapterConfigurationExtensions.AddDependentProcessWatcher(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, System.Collections.Generic.IEnumerable<int>! pids) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
 static Microsoft.Extensions.DependencyInjection.CommonAdapterConfigurationExtensions.AddHostInfo(this DataCore.Adapter.DependencyInjection.IAdapterConfigurationBuilder! builder, System.Action<DataCore.Adapter.Common.HostInfoBuilder!>! configure) -> DataCore.Adapter.DependencyInjection.IAdapterConfigurationBuilder!
 static Microsoft.Extensions.DependencyInjection.CommonAdapterConfigurationExtensions.AddHostInfo(this DataCore.Adapter.DependencyInjection.IAdapterConfigurationBuilder! builder, System.Action<System.IServiceProvider!, DataCore.Adapter.Common.HostInfoBuilder!>! configure) -> DataCore.Adapter.DependencyInjection.IAdapterConfigurationBuilder!
 static Microsoft.Extensions.DependencyInjection.CommonAdapterConfigurationExtensions.WithInstanceId(this DataCore.Adapter.Common.HostInfoBuilder! builder, string! instanceId) -> DataCore.Adapter.Common.HostInfoBuilder!

src/DataCore.Adapter.Templates/src/aschostedadapter/Program.cs

@@ -15,6 +15,12 @@
 // Our adapter settings are stored in adaptersettings.json.
 builder.Configuration.AddJsonFile(Constants.AdapterSettingsFilePath, false, true);
 
+// Parent PID. If specified, we will gracefully shut down if the parent process exits.
+var pid = builder.Configuration.GetValue<int>("AppStoreConnect:Adapter:Host:ParentPid");
+if (pid > 0) {
+    builder.Services.AddDependentProcessWatcher(pid);
+}
+
 // Host instance ID.
 var instanceId = builder.Configuration.GetValue<string>("AppStoreConnect:Adapter:Host:InstanceId");
 if (string.IsNullOrWhiteSpace(instanceId)) {