Reimplement KestrelMetricServer

src/Nethermind/Nethermind.Monitoring/MonitoringService.cs

@@ -81,13 +81,7 @@ public async Task StartAsync()
             }
             if (_exposePort is not null)
             {
-                IMetricServer metricServer = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ?
-                    // MetricServer uses HttpListener which on Windows either needs
-                    // permissions at OS or Admin mode, whereas KestrelMetricServer doesn't need those
-                    new KestrelMetricServer(_exposePort.Value) :
-                    // KestrelMetricServer intercept SIGTERM causing exitcode to be incorrect
-                    new MetricServer(_exposePort.Value);
-                metricServer.Start();
+                new NethermindKestrelMetricServer(_exposePort.Value).Start();
             }
             await Task.Factory.StartNew(() => _metricsController.StartUpdating(), TaskCreationOptions.LongRunning);
             if (_logger.IsInfo) _logger.Info($"Started monitoring for the group: {_options.Group}, instance: {_options.Instance}");

src/Nethermind/Nethermind.Monitoring/NethermindKestrelMetricServer.cs

@@ -0,0 +1,124 @@
+// SPDX-FileCopyrightText: 2023 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+#nullable enable
+using System;
+using System.Net;
+using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Core;
+using Microsoft.Extensions.DependencyInjection;
+using Prometheus;
+
+namespace Nethermind.Monitoring;
+
+/// <summary>
+/// Copy of KestrelMetricServer but does not wait for Ctrl-C so that it does not intercept exit code
+/// </summary>
+public sealed class NethermindKestrelMetricServer : MetricHandler
+{
+    public NethermindKestrelMetricServer(int port, string url = "/metrics", CollectorRegistry? registry = null, X509Certificate2? certificate = null) : this("+", port, url, registry, certificate)
+    {
+    }
+
+    public NethermindKestrelMetricServer(string hostname, int port, string url = "/metrics", CollectorRegistry? registry = null, X509Certificate2? certificate = null) : this(LegacyOptions(hostname, port, url, registry, certificate))
+    {
+    }
+
+    private static KestrelMetricServerOptions LegacyOptions(string hostname, int port, string url, CollectorRegistry? registry, X509Certificate2? certificate) =>
+        new KestrelMetricServerOptions
+        {
+            Hostname = hostname,
+            Port = (ushort)port,
+            Url = url,
+            Registry = registry,
+            TlsCertificate = certificate,
+        };
+
+    public NethermindKestrelMetricServer(KestrelMetricServerOptions options)
+    {
+        _hostname = options.Hostname;
+        _port = options.Port;
+        _url = options.Url;
+        _certificate = options.TlsCertificate;
+
+        // We use one callback to apply the legacy settings, and from within this we call the real callback.
+        _configureExporter = settings =>
+        {
+            // Legacy setting, may be overridden by ConfigureExporter.
+            settings.Registry = options.Registry;
+
+            if (options.ConfigureExporter != null)
+                options.ConfigureExporter(settings);
+        };
+    }
+
+    private readonly string _hostname;
+    private readonly int _port;
+    private readonly string _url;
+
+    private readonly X509Certificate2? _certificate;
+
+    private readonly Action<MetricServerMiddleware.Settings> _configureExporter;
+
+    protected override Task StartServer(CancellationToken cancel)
+    {
+        var s = _certificate != null ? "s" : "";
+        var hostAddress = $"http{s}://{_hostname}:{_port}";
+
+        // If the caller needs to customize any of this, they can just set up their own web host and inject the middleware.
+        var builder = new WebHostBuilder()
+            .UseKestrel()
+            .UseIISIntegration()
+            .Configure(app =>
+            {
+                app.UseMetricServer(_configureExporter, _url);
+
+                // If there is any URL prefix, we just redirect people going to root URL to our prefix.
+                if (!string.IsNullOrWhiteSpace(_url.Trim('/')))
+                {
+                    app.MapWhen(context => context.Request.Path.Value?.Trim('/') == "",
+                        configuration =>
+                        {
+                            configuration.Use((HttpContext context, RequestDelegate next) =>
+                            {
+                                context.Response.Redirect(_url);
+                                return Task.CompletedTask;
+                            });
+                        });
+                }
+            });
+
+        if (_certificate != null)
+        {
+            builder = builder.ConfigureServices(services =>
+            {
+                Action<ListenOptions> configureEndpoint = options =>
+                {
+                    options.UseHttps(_certificate);
+                };
+
+                services.Configure<KestrelServerOptions>(options =>
+                {
+                    options.Listen(IPAddress.Any, _port, configureEndpoint);
+                });
+            });
+        }
+        else
+        {
+            builder = builder.UseUrls(hostAddress);
+        }
+
+        var webHost = builder.Build();
+        webHost.Start();
+
+        // This is what changed
+        // return webHost.WaitForShutdownAsync(cancel);
+
+        return webHost.RunAsync(cancel);
+    }
+}