[OpAMP.Client] Add support for plain http transport

src/OpenTelemetry.OpAmp.Client/CHANGELOG.md

@@ -2,6 +2,5 @@
 
 ## Unreleased
 
-* Initial release of
-  `OpenTelemetry.OpAmp.Client`
-  project.
+* Initial release of `OpenTelemetry.OpAmp.Client` project.
+* Added support for OpAMP Plain Http transport.

src/OpenTelemetry.OpAmp.Client/FrameBuilder.cs

@@ -0,0 +1,57 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using Google.Protobuf;
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client;
+
+internal class FrameBuilder : IFrameBuilder
+{
+    private readonly OpAmpClientSettings settings;
+
+    private AgentToServer? currentMessage;
+    private ByteString instanceUid;
+    private ulong sequenceNum;
+
+    public FrameBuilder(OpAmpClientSettings settings)
+    {
+        this.settings = settings;
+        this.instanceUid = ByteString.CopyFrom(this.settings.InstanceUid.ToByteArray());
+    }
+
+    public IFrameBuilder StartBaseMessage()
+    {
+        if (this.currentMessage != null)
+        {
+            throw new InvalidOperationException("Message base is already initialized.");
+        }
+
+        var message = new AgentToServer()
+        {
+            InstanceUid = this.instanceUid,
+            SequenceNum = ++this.sequenceNum,
+        };
+
+        this.currentMessage = message;
+        return this;
+    }
+
+    AgentToServer IFrameBuilder.Build()
+    {
+        if (this.currentMessage == null)
+        {
+            throw new InvalidOperationException("Message base is not initialized.");
+        }
+
+        var message = this.currentMessage;
+        this.currentMessage = null; // Reset for the next message
+
+        return message;
+    }
+
+    public void Reset()
+    {
+        this.currentMessage = null;
+    }
+}

src/OpenTelemetry.OpAmp.Client/FrameDispatcher.cs

@@ -0,0 +1,60 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpenTelemetry.Internal;
+using OpenTelemetry.OpAmp.Client.Transport;
+
+namespace OpenTelemetry.OpAmp.Client;
+
+internal class FrameDispatcher : IDisposable
+{
+    private readonly IOpAmpTransport transport;
+    private readonly FrameBuilder frameBuilder;
+    private readonly SemaphoreSlim syncRoot = new(1, 1);
+
+    public FrameDispatcher(IOpAmpTransport transport, OpAmpClientSettings settings)
+    {
+        Guard.ThrowIfNull(transport, nameof(transport));
+        Guard.ThrowIfNull(settings, nameof(settings));
+
+        this.transport = transport;
+        this.frameBuilder = new FrameBuilder(settings);
+    }
+
+    // TODO: May need to redesign to request only partials
+    // so any other message waiting to be sent can be included to optimize transport usage and locking time.
+    public async Task DispatchServerFrameAsync(CancellationToken token)
+    {
+        await this.syncRoot.WaitAsync(token)
+            .ConfigureAwait(false);
+
+        try
+        {
+            var message = this.frameBuilder
+                .StartBaseMessage()
+                .Build();
+
+            // TODO: change to proper logging
+            Console.WriteLine("Sending identification message.");
+
+            await this.transport.SendAsync(message, token)
+                .ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            // TODO: change to proper logging
+            Console.WriteLine($"[Error]: {ex.Message}");
+
+            this.frameBuilder.Reset(); // Reset the builder in case of failure
+        }
+        finally
+        {
+            this.syncRoot.Release();
+        }
+    }
+
+    public void Dispose()
+    {
+        this.syncRoot.Dispose();
+    }
+}

src/OpenTelemetry.OpAmp.Client/FrameProcessor.cs

@@ -0,0 +1,123 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using System.Buffers;
+using System.Collections.Concurrent;
+using System.Collections.Immutable;
+using OpAmp.Protocol;
+using OpenTelemetry.Internal;
+using OpenTelemetry.OpAmp.Client.Listeners;
+using OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+namespace OpenTelemetry.OpAmp.Client;
+
+internal class FrameProcessor
+{
+    private readonly ConcurrentDictionary<Type, ImmutableList<IOpAmpListener>> listeners = [];
+
+    public void Subscribe<T>(IOpAmpListener<T> listener)
+        where T : IOpAmpMessage
+    {
+        Guard.ThrowIfNull(listener, nameof(listener));
+
+        // It is expected to be much more read-heavy than write-heavy, so we use ImmutableList for thread safety
+        this.listeners.AddOrUpdate(
+            typeof(T),
+            _ => [listener],
+            (_, list) => list.Add(listener));
+    }
+
+    public void Unsubscribe<T>(IOpAmpListener<T> listener)
+        where T : IOpAmpMessage
+    {
+        Guard.ThrowIfNull(listener, nameof(listener));
+
+        this.listeners.AddOrUpdate(
+            typeof(T),
+            _ => ImmutableList<IOpAmpListener>.Empty,
+            (_, list) =>
+            {
+                if (list.Count == 1 && list[0] == listener)
+                {
+                    return ImmutableList<IOpAmpListener>.Empty;
+                }
+
+                return list.Remove(listener);
+            });
+    }
+
+    public void OnServerFrame(ReadOnlySequence<byte> sequence)
+    {
+        this.Deserialize(sequence);
+    }
+
+    private void Deserialize(ReadOnlySequence<byte> sequence)
+    {
+        var message = ServerToAgent.Parser.ParseFrom(sequence);
+
+        if (message.ErrorResponse != null)
+        {
+            this.Dispatch(new ErrorResponseMessage() { ErrorResponse = message.ErrorResponse });
+        }
+
+        if (message.RemoteConfig != null)
+        {
+            this.Dispatch(new RemoteConfigMessage() { RemoteConfig = message.RemoteConfig });
+        }
+
+        if (message.ConnectionSettings != null)
+        {
+            this.Dispatch(new ConnectionSettingsMessage() { ConnectionSettings = message.ConnectionSettings });
+        }
+
+        if (message.PackagesAvailable != null)
+        {
+            this.Dispatch(new PackagesAvailableMessage() { PackagesAvailable = message.PackagesAvailable });
+        }
+
+        if (message.Flags != 0)
+        {
+            this.Dispatch(new FlagsMessage() { Flags = (ServerToAgentFlags)message.Flags });
+        }
+
+        if (message.Capabilities != 0)
+        {
+            this.Dispatch(new CapabilitiesMessage() { Capabilities = (ServerCapabilities)message.Capabilities });
+        }
+
+        if (message.AgentIdentification != null)
+        {
+            this.Dispatch(new AgentIdentificationMessage() { AgentIdentification = message.AgentIdentification });
+        }
+
+        if (message.Command != null)
+        {
+            this.Dispatch(new CommandMessage() { Command = message.Command });
+        }
+
+        if (message.CustomCapabilities != null)
+        {
+            this.Dispatch(new CustomCapabilitiesMessage() { CustomCapabilities = message.CustomCapabilities });
+        }
+
+        if (message.CustomMessage != null)
+        {
+            this.Dispatch(new CustomMessageMessage() { CustomMessage = message.CustomMessage });
+        }
+    }
+
+    private void Dispatch<T>(T message)
+        where T : IOpAmpMessage
+    {
+        if (this.listeners.TryGetValue(typeof(T), out var list))
+        {
+            foreach (var listener in list)
+            {
+                if (listener is IOpAmpListener<T> typedListener)
+                {
+                    typedListener.HandleMessage(message);
+                }
+            }
+        }
+    }
+}

src/OpenTelemetry.OpAmp.Client/IFrameBuilder.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client;
+
+internal interface IFrameBuilder
+{
+    AgentToServer Build();
+}

src/OpenTelemetry.OpAmp.Client/Listeners/IOpAmpListener.cs

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+namespace OpenTelemetry.OpAmp.Client.Listeners;
+
+internal interface IOpAmpListener
+{
+}
+
+internal interface IOpAmpListener<TMessage> : IOpAmpListener
+    where TMessage : IOpAmpMessage
+{
+    void HandleMessage(TMessage message);
+}

src/OpenTelemetry.OpAmp.Client/Listeners/IOpAmpMessage.cs

@@ -0,0 +1,8 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+namespace OpenTelemetry.OpAmp.Client.Listeners;
+
+internal interface IOpAmpMessage
+{
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/AgentIdentificationMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class AgentIdentificationMessage : IOpAmpMessage
+{
+    public AgentIdentification AgentIdentification { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/CapabilitiesMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class CapabilitiesMessage : IOpAmpMessage
+{
+    public ServerCapabilities Capabilities { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/CommandMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class CommandMessage : IOpAmpMessage
+{
+    public ServerToAgentCommand Command { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/ConnectionSettingsMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class ConnectionSettingsMessage : IOpAmpMessage
+{
+    public ConnectionSettingsOffers ConnectionSettings { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/CustomCapabilitiesMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class CustomCapabilitiesMessage : IOpAmpMessage
+{
+    public CustomCapabilities CustomCapabilities { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/CustomMessageMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class CustomMessageMessage : IOpAmpMessage
+{
+    public CustomMessage CustomMessage { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/ErrorResponseMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class ErrorResponseMessage : IOpAmpMessage
+{
+    public ServerErrorResponse ErrorResponse { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/FlagsMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class FlagsMessage : IOpAmpMessage
+{
+    public ServerToAgentFlags Flags { get; set; }
+}

src/OpenTelemetry.OpAmp.Client/Listeners/Messages/PackagesAvailableMessage.cs

@@ -0,0 +1,11 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+using OpAmp.Protocol;
+
+namespace OpenTelemetry.OpAmp.Client.Listeners.Messages;
+
+internal class PackagesAvailableMessage : IOpAmpMessage
+{
+    public PackagesAvailable PackagesAvailable { get; set; }
+}