Improve PrometheusHttpListener options

docs/metrics/getting-started-prometheus-grafana/README.md

@@ -49,10 +49,10 @@ with
 .AddPrometheusHttpListener()
 ```
 
-`PrometheusHttpListener` is a wrapper that contains `PrometheusExporter`.
-With `AddPrometheusHttpListener()`, OpenTelemetry `PrometheusExporter` will export
+`PrometheusHttpListener` is a wrapper that contains `PrometheusExporter`. With
+`AddPrometheusHttpListener()`, OpenTelemetry `PrometheusExporter` will export
 data via the endpoint defined by
-[PrometheusHttpListenerOptions.Prefixes](../../../src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md#prefixes),
+[PrometheusHttpListenerOptions.UriPrefixes](../../../src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md#uriprefixes),
 which is `http://localhost:9464/` by default.
 
 ```mermaid

examples/Console/TestPrometheusExporter.cs

@@ -52,7 +52,7 @@ internal static object Run(int port)
             .AddMeter(MyMeter.Name)
             .AddMeter(MyMeter2.Name)
             .AddPrometheusHttpListener(
-                options => options.Prefixes = new string[] { $"http://localhost:{port}/" })
+                options => options.UriPrefixes = new string[] { $"http://localhost:{port}/" })
             .Build();
 
         var process = Process.GetCurrentProcess();

src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/net462/PublicAPI.Unshipped.txt

@@ -1,6 +1,6 @@
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions
-OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.Prefixes.get -> System.Collections.Generic.IReadOnlyCollection<string>
-OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.Prefixes.set -> void
+OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.UriPrefixes.get -> System.Collections.Generic.IReadOnlyCollection<string>
+OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.UriPrefixes.set -> void
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.PrometheusHttpListenerOptions() -> void
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.ScrapeEndpointPath.get -> string
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.ScrapeEndpointPath.set -> void

src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt

@@ -1,6 +1,6 @@
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions
-OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.Prefixes.get -> System.Collections.Generic.IReadOnlyCollection<string>
-OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.Prefixes.set -> void
+OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.UriPrefixes.get -> System.Collections.Generic.IReadOnlyCollection<string>
+OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.UriPrefixes.set -> void
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.PrometheusHttpListenerOptions() -> void
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.ScrapeEndpointPath.get -> string
 OpenTelemetry.Exporter.Prometheus.PrometheusHttpListenerOptions.ScrapeEndpointPath.set -> void

src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md

@@ -8,6 +8,9 @@
   ([#3430](https://github.com/open-telemetry/opentelemetry-dotnet/pull/3430)
   [#3503](https://github.com/open-telemetry/opentelemetry-dotnet/pull/3503)
   [#3507](https://github.com/open-telemetry/opentelemetry-dotnet/pull/3507))
+* Fixed bug
+  [#2840](https://github.com/open-telemetry/opentelemetry-dotnet/issues/2840).
+  ([#3521](https://github.com/open-telemetry/opentelemetry-dotnet/pull/3521))
 
 ## 1.3.0-rc.2
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListener.cs

@@ -39,14 +39,12 @@ internal sealed class PrometheusHttpListener : IDisposable
         public PrometheusHttpListener(PrometheusExporter exporter, PrometheusHttpListenerOptions options)
         {
             Guard.ThrowIfNull(exporter);
-
-            if ((options.Prefixes?.Count ?? 0) <= 0)
-            {
-                throw new ArgumentException("No Prefixes were specified on PrometheusHttpListenerOptions.");
-            }
+            Guard.ThrowIfNull(options);
 
             this.exporter = exporter;
+
             string path = this.exporter.ScrapeEndpointPath;
+
             if (!path.StartsWith("/"))
             {
                 path = $"/{path}";
@@ -57,9 +55,9 @@ public PrometheusHttpListener(PrometheusExporter exporter, PrometheusHttpListene
                 path = $"{path}/";
             }
 
-            foreach (string prefix in options.Prefixes)
+            foreach (string uriPrefix in options.UriPrefixes)
             {
-                this.httpListener.Prefixes.Add($"{prefix.TrimEnd('/')}{path}");
+                this.httpListener.Prefixes.Add($"{uriPrefix.TrimEnd('/')}{path}");
             }
         }
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs

@@ -25,36 +25,30 @@ namespace OpenTelemetry.Exporter.Prometheus
     /// </summary>
     public class PrometheusHttpListenerOptions
     {
-        private IReadOnlyCollection<string> prefixes = new string[] { "http://localhost:9464/" };
+        private IReadOnlyCollection<string> uriPrefixes = new string[] { "http://localhost:9464/" };
 
         /// <summary>
         /// Gets or sets the path to use for the scraping endpoint. Default value: "/metrics".
         /// </summary>
         public string ScrapeEndpointPath { get; set; } = "/metrics";
 
         /// <summary>
-        /// Gets or sets the prefixes to use for the http listener.
+        /// Gets or sets the URI (Uniform Resource Identifier) prefixes to use for the http listener.
         /// Default value: <c>["http://localhost:9464/"]</c>.
         /// </summary>
-        public IReadOnlyCollection<string> Prefixes
+        public IReadOnlyCollection<string> UriPrefixes
         {
-            get => this.prefixes;
+            get => this.uriPrefixes;
             set
             {
                 Guard.ThrowIfNull(value);
 
-                foreach (string inputUri in value)
+                if (value.Count == 0)
                 {
-                    if (!(Uri.TryCreate(inputUri, UriKind.Absolute, out var uri) &&
-                        (uri.Scheme == Uri.UriSchemeHttp || uri.Scheme == Uri.UriSchemeHttps)))
-                    {
-                        throw new ArgumentException(
-                            "Prometheus HttpListener prefix path should be a valid URI with http/https scheme.",
-                            nameof(this.prefixes));
-                    }
+                    throw new ArgumentException("Empty list provided.", nameof(this.UriPrefixes));
                 }
 
-                this.prefixes = value;
+                this.uriPrefixes = value;
             }
         }
     }

src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md

@@ -15,38 +15,32 @@ instance for Prometheus to scrape.
 
 ### Step 1: Install Package
 
-Install
-
 ```shell
 dotnet add package OpenTelemetry.Exporter.Prometheus.HttpListener
 ```
 
 ### Step 2: Add PrometheusHttpListener
 
-Add and configure `PrometheusHttpListener` with `PrometheusHttpListenerOptions`.
-
-For example:
-
 ```csharp
-using var meterProvider = Sdk.CreateMeterProviderBuilder()
+var meterProvider = Sdk.CreateMeterProviderBuilder()
     .AddMeter(MyMeter.Name)
     .AddPrometheusHttpListener(
-        options => options.Prefixes = new string[] { "http://localhost:9464/" })
+        options => options.UriPrefixes = new string[] { "http://localhost:9464/" })
     .Build();
 ```
 
-### Prefixes
+### UriPrefixes
 
-Defines the prefixes which will be used by the listener. The default value is `["http://localhost:9464/"]`.
-You may specify multiple endpoints.
+Defines one or more URI (Uniform Resource Identifier) prefixes which will be
+used by the HTTP listener. The default value is `["http://localhost:9464/"]`.
 
-For details see:
+Refer to
 [HttpListenerPrefixCollection.Add(String)](https://docs.microsoft.com/dotnet/api/system.net.httplistenerprefixcollection.add)
+for more details.
 
 ### ScrapeEndpointPath
 
-Defines the path for the Prometheus scrape endpoint for by
-`UseOpenTelemetryPrometheusScrapingEndpoint`. Default value: `"/metrics"`.
+Defines the Prometheus scrape endpoint path. Default value: `"/metrics"`.
 
 ## Troubleshooting
 

test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs

@@ -35,38 +35,44 @@ public class PrometheusHttpListenerTests
         [InlineData("https://example.com")]
         [InlineData("http://127.0.0.1")]
         [InlineData("http://example.com", "https://example.com", "http://127.0.0.1")]
-        public void ServerEndpointSanityCheckPositiveTest(params string[] uris)
+        public void UriPrefixesPositiveTest(params string[] uriPrefixes)
         {
             using MeterProvider meterProvider = Sdk.CreateMeterProviderBuilder()
-                .AddPrometheusHttpListener(options => options.Prefixes = uris)
+                .AddPrometheusHttpListener(options => options.UriPrefixes = uriPrefixes)
                 .Build();
         }
 
-        [Theory]
-        [InlineData("")]
-        [InlineData(null)]
-        [InlineData("ftp://example.com")]
-        [InlineData("http://example.com", "https://example.com", "ftp://example.com")]
-        public void ServerEndpointSanityCheckNegativeTest(params string[] uris)
+        [Fact]
+        public void UriPrefixesNull()
         {
-            try
+            Assert.Throws<ArgumentNullException>(() =>
             {
                 using MeterProvider meterProvider = Sdk.CreateMeterProviderBuilder()
-                    .AddPrometheusHttpListener(options => options.Prefixes = uris)
+                    .AddPrometheusHttpListener(options => options.UriPrefixes = null)
                     .Build();
-            }
-            catch (Exception ex)
+            });
+        }
+
+        [Fact]
+        public void UriPrefixesEmptyList()
+        {
+            Assert.Throws<ArgumentException>(() =>
             {
-                if (ex is not ArgumentNullException)
-                {
-                    Assert.Equal("System.ArgumentException", ex.GetType().ToString());
-#if NETFRAMEWORK
-                    Assert.Equal("Prometheus HttpListener prefix path should be a valid URI with http/https scheme.\r\nParameter name: prefixes", ex.Message);
-#else
-                    Assert.Equal("Prometheus HttpListener prefix path should be a valid URI with http/https scheme. (Parameter 'prefixes')", ex.Message);
-#endif
-                }
-            }
+                using MeterProvider meterProvider = Sdk.CreateMeterProviderBuilder()
+                    .AddPrometheusHttpListener(options => options.UriPrefixes = new string[] { })
+                    .Build();
+            });
+        }
+
+        [Fact]
+        public void UriPrefixesInvalid()
+        {
+            Assert.Throws<InvalidOperationException>(() =>
+            {
+                using MeterProvider meterProvider = Sdk.CreateMeterProviderBuilder()
+                    .AddPrometheusHttpListener(options => options.UriPrefixes = new string[] { "ftp://example.com" })
+                    .Build();
+            });
         }
 
         [Fact]
@@ -98,7 +104,7 @@ private async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetri
 
                 provider = Sdk.CreateMeterProviderBuilder()
                     .AddMeter(meter.Name)
-                    .AddPrometheusHttpListener(options => options.Prefixes = new string[] { address })
+                    .AddPrometheusHttpListener(options => options.UriPrefixes = new string[] { address })
                     .Build();
             }
 

test/OpenTelemetry.Tests.Stress.Metrics/Program.cs

@@ -47,7 +47,7 @@ public static void Main()
         using var meterProvider = Sdk.CreateMeterProviderBuilder()
             .AddMeter(TestMeter.Name)
             .AddPrometheusHttpListener(
-                options => options.Prefixes = new string[] { $"http://localhost:9185/" })
+                options => options.UriPrefixes = new string[] { $"http://localhost:9185/" })
             .Build();
 
         Stress(prometheusPort: 9184);

test/OpenTelemetry.Tests.Stress/Skeleton.cs

@@ -76,7 +76,7 @@ public static void Stress(int concurrency = 0, int prometheusPort = 0)
             .AddMeter(meter.Name)
             .AddRuntimeInstrumentation()
             .AddPrometheusHttpListener(
-                options => options.Prefixes = new string[] { $"http://localhost:{prometheusPort}/" })
+                options => options.UriPrefixes = new string[] { $"http://localhost:{prometheusPort}/" })
             .Build() : null;
 
         var statistics = new long[concurrency];