Merge pull request #1 from nohwnd/restrict-access-to-metrics-by-port

Add optional port restriction for /metrics endpoint

Author: phnx47

src/Prometheus.Client.AspNetCore/PrometheusExtensions.cs

@@ -1,7 +1,9 @@
-using System;
+using System;
+using System.Net;
 using System.Threading.Tasks;
 using Prometheus.Client.Collectors;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
 
 namespace Prometheus.Client.AspNetCore
 {
@@ -36,8 +38,8 @@ public static IApplicationBuilder UsePrometheusServer(this IApplicationBuilder a
                 throw new ArgumentException($"MapPath '{options.MapPath}' should start with '/'");
 
             RegisterCollectors(options);
-
-            app.Map(options.MapPath, coreapp =>
+            
+            Action<IApplicationBuilder> addMetricsHandler = coreapp =>
             {
                 coreapp.Run(async context =>
                 {
@@ -51,18 +53,24 @@ public static IApplicationBuilder UsePrometheusServer(this IApplicationBuilder a
 
                     await Task.FromResult(0).ConfigureAwait(false);
                 });
-            });
+            };
+
+            if (options.Port == null)
+            {
+                return app.Map(options.MapPath, addMetricsHandler);
+            }
 
-            return app;
+            Func<HttpContext, bool> portMatches = context => context.Connection.LocalPort == options.Port;
+            return app.Map(options.MapPath, cfg => cfg.MapWhen(portMatches, addMetricsHandler));
         }
 
 
         private static void RegisterCollectors(PrometheusOptions options)
         {
             if (options.UseDefaultCollectors)
             {
-                var metricFactory = options.CollectorRegistryInstance == CollectorRegistry.Instance 
-                    ? Metrics.DefaultFactory 
+                var metricFactory = options.CollectorRegistryInstance == CollectorRegistry.Instance
+                    ? Metrics.DefaultFactory
                     : new MetricFactory(options.CollectorRegistryInstance);
 
                 options.Collectors.AddRange(DefaultCollectors.Get(metricFactory));

src/Prometheus.Client.AspNetCore/PrometheusOptions.cs

@@ -14,6 +14,11 @@ public class PrometheusOptions
         /// </summary>
         public string MapPath { get; set; } = "/metrics";
 
+        /// <summary>
+        ///     When specified only allow access to metrics on this port, otherwise return 404, default = null.
+        /// </summary>
+        public int? Port { get; set; }
+
         /// <summary>
         ///     CollectorRegistry intance
         /// </summary>
@@ -29,4 +34,4 @@ public class PrometheusOptions
         /// </summary>
         public bool UseDefaultCollectors { get; set; } = true;
     }
-}
+}