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Enable servers to log to the clients via ILogger (#229)

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* Enable servers to log to the client via ILogger

* Address feedback
This commit is contained in:
Stephen Toub 2025-04-07 23:16:42 -04:00 • committed by GitHub
commit 3b83ad4103
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1 changed files with 242 additions and 18 deletions
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60
src/ModelContextProtocol/Server/McpServer.cs
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@ -5,7 +5,7 @@ using ModelContextProtocol.Protocol.Types;
using ModelContextProtocol.Shared;
using ModelContextProtocol.Utils;
using ModelContextProtocol.Utils.Json;
using System.Diagnostics;
using System.Runtime.CompilerServices;
namespace ModelContextProtocol.Server;
@ -26,6 +26,13 @@ internal sealed class McpServer : McpEndpoint, IMcpServer
private string _endpointName;
private int _started;
/// <summary>Holds a boxed <see cref="LoggingLevel"/> value for the server.</summary>
/// <remarks>
/// Initialized to non-null the first time SetLevel is used. This is stored as a strong box
/// rather than a nullable to be able to manipulate it atomically.
/// </remarks>
private StrongBox<LoggingLevel>? _loggingLevel;
/// <summary>
/// Creates a new instance of <see cref="McpServer"/>.
/// </summary>
@ -105,6 +112,9 @@ internal sealed class McpServer : McpEndpoint, IMcpServer
/// <inheritdoc />
public override string EndpointName => _endpointName;
/// <inheritdoc />
public LoggingLevel? LoggingLevel => _loggingLevel?.Value;
/// <inheritdoc />
public async Task RunAsync(CancellationToken cancellationToken = default)
{
@ -441,20 +451,48 @@ internal sealed class McpServer : McpEndpoint, IMcpServer
private void SetSetLoggingLevelHandler(McpServerOptions options)
{
if (options.Capabilities?.Logging is not { } loggingCapability)
{
return;
}
if (loggingCapability.SetLoggingLevelHandler is not { } setLoggingLevelHandler)
{
throw new McpException("Logging capability was enabled, but SetLoggingLevelHandler was not specified.");
}
// We don't require that the handler be provided, as we always store the provided
// log level to the server.
var setLoggingLevelHandler = options.Capabilities?.Logging?.SetLoggingLevelHandler;
RequestHandlers.Set(
RequestMethods.LoggingSetLevel,
(request, cancellationToken) => setLoggingLevelHandler(new(this, request), cancellationToken),
(request, cancellationToken) =>
{
// Store the provided level.
if (request is not null)
{
if (_loggingLevel is null)
{
Interlocked.CompareExchange(ref _loggingLevel, new(request.Level), null);
}
_loggingLevel.Value = request.Level;
}
// If a handler was provided, now delegate to it.
if (setLoggingLevelHandler is not null)
{
return setLoggingLevelHandler(new(this, request), cancellationToken);
}
// Otherwise, consider it handled.
return EmptyResult.CompletedTask;
},
McpJsonUtilities.JsonContext.Default.SetLevelRequestParams,
McpJsonUtilities.JsonContext.Default.EmptyResult);
}
/// <summary>Maps a <see cref="LogLevel"/> to a <see cref="LoggingLevel"/>.</summary>
internal static LoggingLevel ToLoggingLevel(LogLevel level) =>
level switch
{
LogLevel.Trace => Protocol.Types.LoggingLevel.Debug,
LogLevel.Debug => Protocol.Types.LoggingLevel.Debug,
LogLevel.Information => Protocol.Types.LoggingLevel.Info,
LogLevel.Warning => Protocol.Types.LoggingLevel.Warning,
LogLevel.Error => Protocol.Types.LoggingLevel.Error,
LogLevel.Critical => Protocol.Types.LoggingLevel.Critical,
_ => Protocol.Types.LoggingLevel.Emergency,
};
}