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Add Trace-level logging for JSON-RPC payloads in transports (#1191)

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Copilot 2026-01-29 11:26:33 -08:00 • committed by GitHub
commit ee8c485d41
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6 changed files with 90 additions and 2 deletions
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2
src/ModelContextProtocol.Core/Client/SseClientSessionTransport.cs
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@ -80,6 +80,8 @@ internal sealed partial class SseClientSessionTransport : TransportBase
messageId = messageWithId.Id.ToString();
}
LogTransportSendingMessageSensitive(message);
using var httpRequestMessage = new HttpRequestMessage(HttpMethod.Post, _messageEndpoint);
StreamableHttpClientSessionTransport.CopyAdditionalHeaders(httpRequestMessage.Headers, _options.AdditionalHeaders, sessionId: null, protocolVersion: null);
var response = await _httpClient.SendAsync(httpRequestMessage, message, cancellationToken).ConfigureAwait(false);

2
src/ModelContextProtocol.Core/Client/StreamClientSessionTransport.cs
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@ -105,6 +105,8 @@ internal class StreamClientSessionTransport : TransportBase
var json = JsonSerializer.Serialize(message, McpJsonUtilities.JsonContext.Default.JsonRpcMessage);
LogTransportSendingMessageSensitive(Name, json);
using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
try
{

2
src/ModelContextProtocol.Core/Client/StreamableHttpClientSessionTransport.cs
View file

@ -75,6 +75,8 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
$"Call {nameof(McpClient)}.{nameof(McpClient.ResumeSessionAsync)} to resume existing sessions.");
}
LogTransportSendingMessageSensitive(message);
using var sendCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, _connectionCts.Token);
cancellationToken = sendCts.Token;

16
src/ModelContextProtocol.Core/Protocol/TransportBase.cs
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@ -1,6 +1,7 @@
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using System.Diagnostics;
using System.Text.Json;
using System.Threading.Channels;
namespace ModelContextProtocol.Protocol;
@ -166,6 +167,21 @@ public abstract partial class TransportBase : ITransport
[LoggerMessage(Level = LogLevel.Error, Message = "{EndpointName} transport send failed for message ID '{MessageId}'.")]
private protected partial void LogTransportSendFailed(string endpointName, string messageId, Exception exception);
[LoggerMessage(Level = LogLevel.Trace, Message = "{EndpointName} transport sending message. Message: '{Message}'.")]
private protected partial void LogTransportSendingMessageSensitive(string endpointName, string message);
/// <summary>
/// Logs a sending message at Trace level if trace logging is enabled.
/// </summary>
/// <param name="message">The JSON-RPC message to log.</param>
private protected void LogTransportSendingMessageSensitive(JsonRpcMessage message)
{
if (_logger.IsEnabled(LogLevel.Trace))
{
LogTransportSendingMessageSensitive(Name, JsonSerializer.Serialize(message, McpJsonUtilities.JsonContext.Default.JsonRpcMessage));
}
}
[LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} transport reading messages.")]
private protected partial void LogTransportEnteringReadMessagesLoop(string endpointName);

4
src/ModelContextProtocol.Core/Server/StreamServerTransport.cs
View file

@ -74,7 +74,9 @@ public class StreamServerTransport : TransportBase
try
{
await JsonSerializer.SerializeAsync(_outputStream, message, McpJsonUtilities.DefaultOptions.GetTypeInfo(typeof(JsonRpcMessage)), cancellationToken).ConfigureAwait(false);
var json = JsonSerializer.Serialize(message, McpJsonUtilities.JsonContext.Default.JsonRpcMessage);
LogTransportSendingMessageSensitive(Name, json);
await _outputStream.WriteAsync(Encoding.UTF8.GetBytes(json), cancellationToken).ConfigureAwait(false);
await _outputStream.WriteAsync(s_newlineBytes, cancellationToken).ConfigureAwait(false);
await _outputStream.FlushAsync(cancellationToken).ConfigureAwait(false);
}

66
tests/ModelContextProtocol.Tests/Transport/StdioServerTransportTests.cs
View file

@ -1,4 +1,5 @@
using ModelContextProtocol.Protocol;
using Microsoft.Extensions.Logging;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Server;
using ModelContextProtocol.Tests.Utils;
using System.IO.Pipelines;
@ -21,6 +22,14 @@ public class StdioServerTransportTests : LoggedTest
InitializationTimeout = TimeSpan.FromSeconds(10),
ServerInstructions = "Test Instructions"
};
// Override the LoggerFactory to use Trace level for testing Trace-level logging
LoggerFactory = Microsoft.Extensions.Logging.LoggerFactory.Create(builder =>
{
builder.AddProvider(XunitLoggerProvider);
builder.AddProvider(MockLoggerProvider);
builder.SetMinimumLevel(LogLevel.Trace);
});
}
[Fact(Skip="https://github.com/modelcontextprotocol/csharp-sdk/issues/143")]
@ -193,4 +202,59 @@ public class StdioServerTransportTests : LoggedTest
Assert.True(magnifyingGlassFound, "Magnifying glass emoji not found in result");
Assert.True(rocketFound, "Rocket emoji not found in result");
}
[Fact]
public async Task SendMessageAsync_Should_Log_At_Trace_Level()
{
// Arrange
using var output = new MemoryStream();
await using var transport = new StreamServerTransport(
new Pipe().Reader.AsStream(),
output,
loggerFactory: LoggerFactory);
// Act
var message = new JsonRpcRequest { Method = "test", Id = new RequestId(44) };
await transport.SendMessageAsync(message, TestContext.Current.CancellationToken);
// Assert
var traceLogMessages = MockLoggerProvider.LogMessages
.Where(x => x.LogLevel == LogLevel.Trace && x.Message.Contains("transport sending message"))
.ToList();
Assert.NotEmpty(traceLogMessages);
Assert.Contains(traceLogMessages, x => x.Message.Contains("\"method\":\"test\"") && x.Message.Contains("\"id\":44"));
}
[Fact]
public async Task ReadMessagesAsync_Should_Log_Received_At_Trace_Level()
{
// Arrange
var message = new JsonRpcRequest { Method = "test", Id = new RequestId(99) };
var json = JsonSerializer.Serialize(message, McpJsonUtilities.DefaultOptions);
Pipe pipe = new();
using var input = pipe.Reader.AsStream();
await using var transport = new StreamServerTransport(
input,
Stream.Null,
loggerFactory: LoggerFactory);
// Act
await pipe.Writer.WriteAsync(Encoding.UTF8.GetBytes($"{json}\n"), TestContext.Current.CancellationToken);
// Wait for the message to be processed
var canRead = await transport.MessageReader.WaitToReadAsync(TestContext.Current.CancellationToken);
Assert.True(canRead, "Nothing to read here from transport message reader");
// Assert
var traceLogMessages = MockLoggerProvider.LogMessages
.Where(x => x.LogLevel == LogLevel.Trace && x.Message.Contains("transport received message"))
.ToList();
Assert.NotEmpty(traceLogMessages);
Assert.Contains(traceLogMessages, x => x.Message.Contains("\"method\":\"test\"") && x.Message.Contains("\"id\":99"));
}
}