feat(logging): 添加日志采样过滤器和统计追加器功能

- 实现 SamplingFilter 类用于限制高频日志输出，支持线程安全的采样控制
- 添加 StatisticsAppender 类用于收集日志指标，包括总数量、错误率、级别分布等统计信息
- 提供时间窗口内的采样机制，可配置采样率和时间窗口参数
- 实现完整的统计报告生成功能，支持按级别和日志记录器分类展示
- 添加线程安全的数据结构确保并发环境下的数据一致性
- 提供统计重置和数据查询接口便于监控和调试

GFramework.Core/logging/appenders/StatisticsAppender.cs

@@ -0,0 +1,163 @@
+using System.Collections.Concurrent;
+using System.Text;
+using GFramework.Core.Abstractions.logging;
+
+namespace GFramework.Core.logging.appenders;
+
+/// <summary>
+///     日志统计 Appender，用于收集日志指标
+///     线程安全：所有方法都是线程安全的
+/// </summary>
+public sealed class StatisticsAppender : ILogAppender
+{
+    private readonly ConcurrentDictionary<LogLevel, long> _levelCounts = new();
+    private readonly ConcurrentDictionary<string, long> _loggerCounts = new();
+    private long _errorCount;
+    private DateTime _startTime = DateTime.UtcNow;
+    private long _totalCount;
+
+    /// <summary>
+    ///     获取总日志数量
+    /// </summary>
+    public long TotalCount => Interlocked.Read(ref _totalCount);
+
+    /// <summary>
+    ///     获取错误日志数量（Error + Fatal）
+    /// </summary>
+    public long ErrorCount => Interlocked.Read(ref _errorCount);
+
+    /// <summary>
+    ///     获取统计开始时间
+    /// </summary>
+    public DateTime StartTime => _startTime;
+
+    /// <summary>
+    ///     获取运行时长
+    /// </summary>
+    public TimeSpan Uptime => DateTime.UtcNow - _startTime;
+
+    /// <summary>
+    ///     获取错误率（错误数 / 总数）
+    /// </summary>
+    public double ErrorRate
+    {
+        get
+        {
+            var total = TotalCount;
+            return total == 0 ? 0 : (double)ErrorCount / total;
+        }
+    }
+
+    /// <summary>
+    ///     追加日志条目
+    /// </summary>
+    public void Append(LogEntry entry)
+    {
+        // 增加总计数
+        Interlocked.Increment(ref _totalCount);
+
+        // 增加级别计数
+        _levelCounts.AddOrUpdate(entry.Level, 1, (_, count) => count + 1);
+
+        // 增加日志记录器计数
+        _loggerCounts.AddOrUpdate(entry.LoggerName, 1, (_, count) => count + 1);
+
+        // 如果是错误级别，增加错误计数
+        if (entry.Level >= LogLevel.Error)
+        {
+            Interlocked.Increment(ref _errorCount);
+        }
+    }
+
+    /// <summary>
+    ///     刷新缓冲区（此 Appender 无需刷新）
+    /// </summary>
+    public void Flush()
+    {
+        // 统计 Appender 不需要刷新
+    }
+
+    /// <summary>
+    ///     获取指定级别的日志数量
+    /// </summary>
+    public long GetCountByLevel(LogLevel level)
+    {
+        return _levelCounts.TryGetValue(level, out var count) ? count : 0;
+    }
+
+    /// <summary>
+    ///     获取指定日志记录器的日志数量
+    /// </summary>
+    public long GetCountByLogger(string loggerName)
+    {
+        return _loggerCounts.TryGetValue(loggerName, out var count) ? count : 0;
+    }
+
+    /// <summary>
+    ///     获取所有级别的日志数量
+    /// </summary>
+    public IReadOnlyDictionary<LogLevel, long> GetLevelCounts()
+    {
+        return new Dictionary<LogLevel, long>(_levelCounts);
+    }
+
+    /// <summary>
+    ///     获取所有日志记录器的日志数量
+    /// </summary>
+    public IReadOnlyDictionary<string, long> GetLoggerCounts()
+    {
+        return new Dictionary<string, long>(_loggerCounts);
+    }
+
+    /// <summary>
+    ///     重置所有统计数据
+    /// </summary>
+    public void Reset()
+    {
+        Interlocked.Exchange(ref _totalCount, 0);
+        Interlocked.Exchange(ref _errorCount, 0);
+        _levelCounts.Clear();
+        _loggerCounts.Clear();
+        _startTime = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    ///     生成统计报告
+    /// </summary>
+    public string GenerateReport()
+    {
+        var report = new StringBuilder();
+        report.AppendLine("=== 日志统计报告 ===");
+        report.AppendLine($"统计时间: {_startTime:yyyy-MM-dd HH:mm:ss} - {DateTime.UtcNow:yyyy-MM-dd HH:mm:ss}");
+        report.AppendLine($"运行时长: {Uptime}");
+        report.AppendLine($"总日志数: {TotalCount}");
+        report.AppendLine($"错误日志数: {ErrorCount}");
+        report.AppendLine($"错误率: {ErrorRate:P2}");
+        report.AppendLine();
+
+        report.AppendLine("按级别统计:");
+        foreach (var level in Enum.GetValues<LogLevel>())
+        {
+            var count = GetCountByLevel(level);
+            if (count > 0)
+            {
+                var percentage = (double)count / TotalCount;
+                report.AppendLine($"  {level}: {count} ({percentage:P2})");
+            }
+        }
+
+        report.AppendLine();
+        report.AppendLine("按日志记录器统计 (Top 10):");
+        var topLoggers = _loggerCounts
+            .OrderByDescending(kvp => kvp.Value)
+            .Take(10);
+
+        foreach (var (logger, count) in topLoggers)
+        {
+            var percentage = (double)count / TotalCount;
+            report.AppendLine($"  {logger}: {count} ({percentage:P2})");
+        }
+
+        return report.ToString();
+    }
+}

GFramework.Core/logging/filters/SamplingFilter.cs

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+using System.Collections.Concurrent;
+using GFramework.Core.Abstractions.logging;
+
+namespace GFramework.Core.logging.filters;
+
+/// <summary>
+///     日志采样过滤器，用于限制高频日志的输出
+///     线程安全：所有方法都是线程安全的
+/// </summary>
+public sealed class SamplingFilter : ILogFilter
+{
+    private readonly int _sampleRate;
+    private readonly ConcurrentDictionary<string, SamplingState> _samplingStates = new();
+    private readonly TimeSpan _timeWindow;
+
+    /// <summary>
+    ///     创建日志采样过滤器
+    /// </summary>
+    /// <param name="sampleRate">采样率（每 N 条日志保留 1 条）</param>
+    /// <param name="timeWindow">时间窗口（在此时间内应用采样）</param>
+    public SamplingFilter(int sampleRate, TimeSpan timeWindow)
+    {
+        if (sampleRate <= 0)
+            throw new ArgumentException("Sample rate must be greater than 0", nameof(sampleRate));
+
+        if (timeWindow <= TimeSpan.Zero)
+            throw new ArgumentException("Time window must be greater than zero", nameof(timeWindow));
+
+        _sampleRate = sampleRate;
+        _timeWindow = timeWindow;
+    }
+
+    /// <summary>
+    ///     判断是否应该记录该日志条目
+    /// </summary>
+    public bool ShouldLog(LogEntry entry)
+    {
+        // 为每个日志记录器维护独立的采样状态
+        var key = entry.LoggerName;
+        var state = _samplingStates.GetOrAdd(key, _ => new SamplingState());
+
+        return state.ShouldLog(_sampleRate, _timeWindow);
+    }
+
+    /// <summary>
+    ///     采样状态
+    /// </summary>
+    private sealed class SamplingState
+    {
+        private readonly object _lock = new();
+        private long _count;
+        private DateTime _windowStart = DateTime.UtcNow;
+
+        public bool ShouldLog(int sampleRate, TimeSpan timeWindow)
+        {
+            lock (_lock)
+            {
+                var now = DateTime.UtcNow;
+
+                // 检查是否需要重置时间窗口
+                if (now - _windowStart >= timeWindow)
+                {
+                    _windowStart = now;
+                    _count = 0;
+                }
+
+                _count++;
+
+                // 每 N 条保留 1 条
+                return _count % sampleRate == 1;
+            }
+        }
+    }
+}