Add structured logging with mcpd-compatible log format (#10)

Author: peteski22

README.md

@@ -132,7 +132,15 @@ public override Task<HTTPResponse> HandleRequest(HTTPRequest request, Grpc.Core.
 
 ### Logging
 
-Plugins that extend `BasePlugin` have access to an `ILogger` instance via the `Logger` property. This allows plugins to emit structured logs that appear in the host application's output.
+Plugins that extend `BasePlugin` have access to an `ILogger` instance via the `Logger` property. The SDK automatically provides a default logger that outputs logs in a format compatible with mcpd's log level inference:
+
+```
+[INFO] Plugin server listening on unix /var/...
+[WARN] Rate limit exceeded
+[ERROR] Failed to process request
+```
+
+This format allows mcpd to properly categorize log messages by severity.
 
 ```csharp
 using Microsoft.Extensions.Logging;
@@ -142,13 +150,13 @@ public class MyPlugin : BasePlugin
 {
     public override Task<Empty> Configure(PluginConfig request, Grpc.Core.ServerCallContext context)
     {
-        Logger?.LogInformation("Plugin configured with {Count} settings", request.Settings.Count);
+        Logger.LogInformation("Plugin configured with {Count} settings", request.Settings.Count);
         return Task.FromResult(new Empty());
     }
 
     public override Task<HTTPResponse> HandleRequest(HTTPRequest request, Grpc.Core.ServerCallContext context)
     {
-        Logger?.LogInformation("Processing request: {Method} {Path}", request.Method, request.Path);
+        Logger.LogInformation("Processing request: {Method} {Path}", request.Method, request.Path);
 
         // Your plugin logic here.
 
@@ -157,7 +165,20 @@ public class MyPlugin : BasePlugin
 }
 ```
 
-The SDK automatically suppresses ASP.NET Core framework logs at the Info level to reduce noise. Plugin logs at Info level and above will appear normally in the host application's output.
+For advanced scenarios, you can provide your own logger:
+
+```csharp
+var loggerFactory = LoggerFactory.Create(builder =>
+{
+    builder.AddJsonConsole();
+    builder.SetMinimumLevel(LogLevel.Debug);
+});
+var logger = loggerFactory.CreateLogger<MyPlugin>();
+
+return await PluginServer.Serve<MyPlugin>(args, logger);
+```
+
+The SDK automatically suppresses ASP.NET Core framework logs at the Info level to reduce noise.
 
 ## Running Your Plugin
 

src/MozillaAI.Mcpd.Plugins.Sdk/BasePlugin.cs

@@ -1,6 +1,7 @@
 using Google.Protobuf.WellKnownTypes;
 using Grpc.Core;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
 
 namespace MozillaAI.Mcpd.Plugins.V1;
 
@@ -46,9 +47,9 @@ namespace MozillaAI.Mcpd.Plugins.V1;
 public class BasePlugin : Plugin.PluginBase
 {
     /// <summary>
-    /// Logger instance for the plugin. Available after SetLogger is called by the SDK.
+    /// Logger instance for the plugin.
     /// </summary>
-    protected ILogger? Logger { get; private set; }
+    protected ILogger Logger { get; private set; } = NullLogger.Instance;
 
     /// <summary>
     /// SetLogger is called by the SDK to provide a logger to the plugin.

src/MozillaAI.Mcpd.Plugins.Sdk/McpdLogFormatter.cs

@@ -0,0 +1,48 @@
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Logging.Console;
+
+namespace MozillaAI.Mcpd.Plugins.V1;
+
+/// <summary>
+/// Console formatter that outputs log messages in a format compatible with mcpd's log inference.
+/// </summary>
+internal sealed class McpdLogFormatter : ConsoleFormatter
+{
+    public McpdLogFormatter() : base("mcpd")
+    {
+    }
+
+    public override void Write<TState>(in LogEntry<TState> logEntry, IExternalScopeProvider? scopeProvider, TextWriter textWriter)
+    {
+        var message = logEntry.Formatter(logEntry.State, logEntry.Exception);
+        if (string.IsNullOrEmpty(message))
+        {
+            return;
+        }
+
+        var levelString = GetLevelString(logEntry.LogLevel);
+        textWriter.Write(levelString);
+        textWriter.Write(' ');
+        textWriter.WriteLine(message);
+
+        if (logEntry.Exception != null)
+        {
+            textWriter.WriteLine(logEntry.Exception.ToString());
+        }
+    }
+
+    private static string GetLevelString(LogLevel logLevel)
+    {
+        return logLevel switch
+        {
+            LogLevel.Trace => "[TRACE]",
+            LogLevel.Debug => "[DEBUG]",
+            LogLevel.Information => "[INFO]",
+            LogLevel.Warning => "[WARN]",
+            LogLevel.Error => "[ERROR]",
+            LogLevel.Critical => "[ERROR]",
+            _ => "[INFO]"
+        };
+    }
+}

src/MozillaAI.Mcpd.Plugins.Sdk/PluginServer.cs

@@ -4,8 +4,8 @@
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Server.Kestrel.Core;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Console;
 
 namespace MozillaAI.Mcpd.Plugins.V1;
 
@@ -31,20 +31,38 @@ public static class PluginServer
     /// </summary>
     /// <typeparam name="T">The plugin implementation type that inherits from Plugin.PluginBase.</typeparam>
     /// <param name="args">Command-line arguments.</param>
+    /// <param name="logger">Optional logger instance. If null, a default console logger is created.</param>
     /// <returns>Exit code (0 for success, 1 for error).</returns>
-    public static async Task<int> Serve<T>(string[] args) where T : Plugin.PluginBase, new()
+    public static async Task<int> Serve<T>(string[] args, ILogger? logger = null) where T : Plugin.PluginBase, new()
     {
-        return await Serve(new T(), args);
+        return await Serve(new T(), args, logger);
     }
 
     /// <summary>
     /// Starts a gRPC server for the specified plugin instance.
     /// </summary>
     /// <param name="implementation">The plugin implementation instance.</param>
     /// <param name="args">Command-line arguments.</param>
+    /// <param name="logger">Optional logger instance. If null, a default console logger is created.</param>
     /// <returns>Exit code (0 for success, 1 for error).</returns>
-    public static async Task<int> Serve(Plugin.PluginBase implementation, string[] args)
+    public static async Task<int> Serve(Plugin.PluginBase implementation, string[] args, ILogger? logger = null)
     {
+        // Create default console logger if none provided.
+        logger ??= LoggerFactory.Create(builder =>
+        {
+            builder.AddConsole(options => options.FormatterName = "mcpd");
+            builder.AddConsoleFormatter<McpdLogFormatter, ConsoleFormatterOptions>();
+            builder.AddFilter("Microsoft.AspNetCore", LogLevel.Warning);
+            builder.AddFilter("Microsoft.Extensions", LogLevel.Warning);
+            builder.AddFilter("Microsoft.Hosting", LogLevel.Warning);
+        }).CreateLogger(implementation.GetType());
+
+        // Provide logger to BasePlugin implementations.
+        if (implementation is BasePlugin basePlugin)
+        {
+            basePlugin.SetLogger(logger);
+        }
+
         var addressOption = new Option<string>(
             name: "--address",
             description: "gRPC address (socket path for unix, host:port for tcp)")
@@ -63,27 +81,25 @@ public static async Task<int> Serve(Plugin.PluginBase implementation, string[] a
             networkOption
         };
 
-        rootCommand.SetHandler(async (address, network) =>
-        {
-            await RunServer(implementation, address, network);
-        }, addressOption, networkOption);
+        rootCommand.SetHandler(async (address, network) => await RunServer(implementation, address, network, logger), addressOption, networkOption);
 
         return await rootCommand.InvokeAsync(args);
     }
 
-    private static async Task RunServer(Plugin.PluginBase implementation, string address, string network)
+    private static async Task RunServer(Plugin.PluginBase implementation, string address, string network, ILogger logger)
     {
         var builder = WebApplication.CreateSlimBuilder();
 
-        // Suppress ASP.NET Core diagnostic logs but allow plugin logs.
+        // Suppress ASP.NET Core diagnostic logs.
         builder.Logging.ClearProviders();
-        builder.Logging.AddConsole();
+        builder.Logging.AddConsole(options => options.FormatterName = "mcpd");
+        builder.Logging.AddConsoleFormatter<McpdLogFormatter, ConsoleFormatterOptions>();
         builder.Logging.AddFilter("Microsoft.AspNetCore", LogLevel.Warning);
         builder.Logging.AddFilter("Microsoft.Extensions", LogLevel.Warning);
         builder.Logging.AddFilter("Microsoft.Hosting", LogLevel.Warning);
 
         // Configure Kestrel.
-        builder.WebHost.ConfigureKestrel((context, serverOptions) =>
+        builder.WebHost.ConfigureKestrel((_, serverOptions) =>
         {
             if (network.Equals("unix", StringComparison.OrdinalIgnoreCase))
             {
@@ -129,7 +145,8 @@ private static async Task RunServer(Plugin.PluginBase implementation, string add
         // Map gRPC service.
         app.MapGrpcService<PluginServiceAdapter>();
 
-        Console.WriteLine($"Plugin server listening on {network} {address}");
+        logger.LogInformation("Plugin server listening on {Network} {Address}", network, address);
+
 
         try
         {
@@ -152,16 +169,9 @@ private class PluginServiceAdapter : Plugin.PluginBase
     {
         private readonly Plugin.PluginBase _implementation;
 
-        public PluginServiceAdapter(Plugin.PluginBase implementation, ILoggerFactory loggerFactory)
+        public PluginServiceAdapter(Plugin.PluginBase implementation)
         {
             _implementation = implementation;
-
-            // Provide logger to BasePlugin implementations.
-            if (_implementation is BasePlugin basePlugin)
-            {
-                var logger = loggerFactory.CreateLogger(_implementation.GetType());
-                basePlugin.SetLogger(logger);
-            }
         }
 
         public override Task<Google.Protobuf.WellKnownTypes.Empty> Configure(PluginConfig request, Grpc.Core.ServerCallContext context)