Add HttpClientFactory setting to OpAmpClientSettings

src/OpenTelemetry.OpAmp.Client/.publicApi/PublicAPI.Unshipped.txt

@@ -36,6 +36,8 @@ OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.ConnectionType.get -> Op
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.ConnectionType.set -> void
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.Heartbeat.get -> OpenTelemetry.OpAmp.Client.Settings.HeartbeatSettings!
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.Heartbeat.set -> void
+OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.HttpClientFactory.get -> System.Func<System.Net.Http.HttpClient!>!
+OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.HttpClientFactory.set -> void
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.Identification.get -> OpenTelemetry.OpAmp.Client.Settings.IdentificationSettings!
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.Identification.set -> void
 OpenTelemetry.OpAmp.Client.Settings.OpAmpClientSettings.InstanceUid.get -> System.Guid

src/OpenTelemetry.OpAmp.Client/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Add setting to configure the factory used to create `HttpClient` instances
+  used for the OpAMP Plain HTTP transport.
+  ([#3589](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/3589))
+
 ## 0.1.0-alpha.3
 
 Released 2025-Nov-13

src/OpenTelemetry.OpAmp.Client/Internal/Transport/Http/PlainHttpTransport.cs

@@ -8,30 +8,24 @@
 using Google.Protobuf;
 using OpenTelemetry.Internal;
 using OpenTelemetry.OpAmp.Client.Internal.Utils;
+using OpenTelemetry.OpAmp.Client.Settings;
 
 namespace OpenTelemetry.OpAmp.Client.Internal.Transport.Http;
 
 internal sealed class PlainHttpTransport : IOpAmpTransport, IDisposable
 {
     private readonly Uri uri;
     private readonly HttpClient httpClient;
-    private readonly HttpClientHandler handler;
     private readonly FrameProcessor processor;
 
-    public PlainHttpTransport(Uri serverUrl, FrameProcessor processor)
+    public PlainHttpTransport(OpAmpClientSettings settings, FrameProcessor processor)
     {
-        Guard.ThrowIfNull(serverUrl, nameof(serverUrl));
+        Guard.ThrowIfNull(settings, nameof(settings));
         Guard.ThrowIfNull(processor, nameof(processor));
 
-        this.uri = serverUrl;
+        this.uri = settings.ServerUrl;
         this.processor = processor;
-        this.handler = new HttpClientHandler
-        {
-            // Trust all certificates
-            ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true,
-        };
-
-        this.httpClient = new HttpClient(this.handler);
+        this.httpClient = settings.HttpClientFactory();
     }
 
     public async Task SendAsync<T>(T message, CancellationToken token)
@@ -62,6 +56,5 @@ public async Task SendAsync<T>(T message, CancellationToken token)
     public void Dispose()
     {
         this.httpClient?.Dispose();
-        this.handler?.Dispose();
     }
 }

src/OpenTelemetry.OpAmp.Client/OpAmpClient.cs

@@ -93,7 +93,7 @@ private static IOpAmpTransport ConstructTransport(OpAmpClientSettings settings,
         return settings.ConnectionType switch
         {
             ConnectionType.WebSocket => new WsTransport(settings.ServerUrl, processor),
-            ConnectionType.Http => new PlainHttpTransport(settings.ServerUrl, processor),
+            ConnectionType.Http => new PlainHttpTransport(settings, processor),
             _ => throw new NotSupportedException("Unsupported transport type"),
         };
     }

src/OpenTelemetry.OpAmp.Client/Settings/OpAmpClientSettings.cs

@@ -1,13 +1,21 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#if NETFRAMEWORK
+using System.Net.Http;
+#endif
+
+using OpenTelemetry.Internal;
+
 namespace OpenTelemetry.OpAmp.Client.Settings;
 
 /// <summary>
 /// OpAMP client settings.
 /// </summary>
 public sealed class OpAmpClientSettings
 {
+    private readonly Func<HttpClient> defaultHttpClientFactory = () => new HttpClient();
+
     private Uri? serverUrl;
 
     /// <summary>
@@ -91,4 +99,27 @@ public Uri ServerUrl
     /// Gets or sets the heartbeat settings.
     /// </summary>
     public HeartbeatSettings Heartbeat { get; set; } = new();
+
+    /// <summary>
+    /// Gets or sets the factory function called to create the <see
+    /// cref="HttpClient"/> instance that will be used at runtime to
+    /// transmit OpAmp messages over HTTP. The returned instance will
+    /// be reused for all communication.
+    /// </summary>
+    /// <remarks>
+    /// Notes:
+    /// <list type="bullet">
+    /// <item>This is only invoked for the <see
+    /// cref="ConnectionType.Http"/> protocol.</item>
+    /// </list>
+    /// </remarks>
+    public Func<HttpClient> HttpClientFactory
+    {
+        get => field ?? this.defaultHttpClientFactory;
+        set
+        {
+            Guard.ThrowIfNull(value);
+            field = value;
+        }
+    }
 }

test/OpenTelemetry.OpAmp.Client.Tests/PlainHttpTransportTest.cs

@@ -1,8 +1,13 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#if NETFRAMEWORK
+using System.Net.Http;
+#endif
+
 using OpenTelemetry.OpAmp.Client.Internal;
 using OpenTelemetry.OpAmp.Client.Internal.Transport.Http;
+using OpenTelemetry.OpAmp.Client.Settings;
 using OpenTelemetry.OpAmp.Client.Tests.Mocks;
 using OpenTelemetry.OpAmp.Client.Tests.Tools;
 using Xunit;
@@ -19,12 +24,13 @@ public async Task PlainHttpTransport_SendReceiveCommunication(bool useSmallPacke
         // Arrange
         using var opAmpServer = new OpAmpFakeHttpServer(useSmallPackets);
         var opAmpEndpoint = opAmpServer.Endpoint;
+        var settings = new OpAmpClientSettings { ServerUrl = opAmpEndpoint };
 
         using var mockListener = new MockListener();
         var frameProcessor = new FrameProcessor();
         frameProcessor.Subscribe(mockListener);
 
-        var httpTransport = new PlainHttpTransport(opAmpEndpoint, frameProcessor);
+        var httpTransport = new PlainHttpTransport(settings, frameProcessor);
 
         var mockFrame = FrameGenerator.GenerateMockAgentFrame(useSmallPackets);
 
@@ -42,4 +48,37 @@ public async Task PlainHttpTransport_SendReceiveCommunication(bool useSmallPacke
         Assert.Single(clientReceivedFrames);
         Assert.StartsWith("This is a mock server frame for testing purposes.", receivedTextData);
     }
+
+    [Fact]
+    public async Task PlainHttpTransport_UsesConfiguredHttpClientFactory()
+    {
+        // Arrange
+        using var opAmpServer = new OpAmpFakeHttpServer(false);
+        var opAmpEndpoint = opAmpServer.Endpoint;
+        var settings = new OpAmpClientSettings
+        {
+            ServerUrl = opAmpEndpoint,
+            HttpClientFactory = () =>
+            {
+                var client = new HttpClient();
+                client.DefaultRequestHeaders.Add("X-Custom-Header", "CustomValue");
+                return client;
+            },
+        };
+
+        using var mockListener = new MockListener();
+        var frameProcessor = new FrameProcessor();
+        frameProcessor.Subscribe(mockListener);
+
+        var httpTransport = new PlainHttpTransport(settings, frameProcessor);
+
+        var mockFrame = FrameGenerator.GenerateMockAgentFrame(false);
+
+        // Act
+        await httpTransport.SendAsync(mockFrame.Frame, CancellationToken.None);
+
+        // Assert
+        var serverReceivedHeaders = opAmpServer.GetHeaders();
+        Assert.Contains(serverReceivedHeaders, headers => headers["X-Custom-Header"] == "CustomValue");
+    }
 }

test/OpenTelemetry.OpAmp.Client.Tests/Tools/OpAmpFakeHttpServer.cs

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 using System.Collections.Concurrent;
+using System.Collections.Specialized;
 using System.Net;
 using OpAmp.Proto.V1;
 using OpenTelemetry.Tests;
@@ -12,6 +13,7 @@ internal class OpAmpFakeHttpServer : IDisposable
 {
     private readonly IDisposable httpServer;
     private readonly BlockingCollection<AgentToServer> frames = [];
+    private readonly List<NameValueCollection> receivedHeaders = [];
 
     public OpAmpFakeHttpServer(bool useSmallPackets)
     {
@@ -21,6 +23,14 @@ public OpAmpFakeHttpServer(bool useSmallPackets)
                 var frame = ProcessReceive(context.Request);
                 this.frames.Add(frame);
 
+                var headersCopy = new NameValueCollection();
+                foreach (var key in context.Request.Headers.AllKeys)
+                {
+                    headersCopy.Add(key, context.Request.Headers[key]);
+                }
+
+                this.receivedHeaders.Add(headersCopy);
+
                 var response = GenerateResponse(frame, useSmallPackets);
 
                 context.Response.StatusCode = (int)HttpStatusCode.OK;
@@ -40,6 +50,11 @@ public IReadOnlyCollection<AgentToServer> GetFrames()
         return this.frames.ToArray();
     }
 
+    public IReadOnlyList<NameValueCollection> GetHeaders()
+    {
+        return this.receivedHeaders.AsReadOnly();
+    }
+
     public void Dispose()
     {
         this.httpServer.Dispose();