chore: initial project import

backend/src/Monitor.Backend.Application/Live/HotLayerBackfill.cs

@@ -0,0 +1,67 @@
+using Fleet.Core;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Monitor.Protocol;
+
+namespace Monitor.Backend.Application;
+
+/// <summary>重启后热层为空：从原始块回填最近 1 小时（低优先级、逐块让出）。完成之前查询规划器不会选用热层。</summary>
+public sealed partial class HotLayerBackfill : BackgroundService
+{
+    private readonly HotLayer _hot;
+    private readonly IRawStore _raw;
+    private readonly TimeProvider _time;
+    private readonly ILogger<HotLayerBackfill> _logger;
+
+    public HotLayerBackfill(HotLayer hot, IRawStore raw, TimeProvider time, ILogger<HotLayerBackfill> logger)
+    {
+        _hot = hot;
+        _raw = raw;
+        _time = time;
+        _logger = logger;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        try
+        {
+            await RunAsync(stoppingToken);
+        }
+        catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+        {
+            // 正常停止
+        }
+        catch (Exception ex)
+        {
+            // 回填失败不应该让热层永远不可用：标记就绪，缺的部分会通过降级到 10s 层之外的查询体现
+            LogFailed(ex);
+            _hot.MarkReady();
+        }
+    }
+
+    /// <summary>回填（也供测试直接调用）。</summary>
+    public async Task RunAsync(CancellationToken ct)
+    {
+        long now = _time.GetUtcNow().ToUnixTimeMilliseconds();
+        long from = now - (long)HotLayer.Retention.TotalMilliseconds - 600_000;
+        foreach ((NodeId agent, string series) in await _raw.ListSeriesAsync(from, now, ct))
+        {
+            IReadOnlyList<RawChunkMeta> metas = await _raw.FindAsync(new RawQuery(agent, series, FromMs: from, ToMs: now, Limit: 2000), ct);
+            foreach (RawChunkMeta meta in metas.Where(m => m.TestId is null))
+            {
+                byte[]? bytes = await _raw.ReadAsync(meta, ct);
+                if (bytes is not null && RawChunkCodec.Decode(bytes).TryGet(out RawChunk? chunk, out _))
+                {
+                    _hot.Merge(agent, series, chunk);
+                }
+
+                await Task.Yield();
+            }
+        }
+
+        _hot.MarkReady();
+    }
+
+    [LoggerMessage(Level = LogLevel.Error, Message = "hot layer backfill failed")]
+    private partial void LogFailed(Exception exception);
+}