fleet: send log counters in heartbeats and pull the text on demand

Heartbeats carry per-level counts, the most frequent log types (a stable hash of the message) and the newest id, no text. The node keeps its last 2048 lines; moshiro.logs.fetch lets the backend pull them. The log page pulls when it is open, and the backend pulls warnings and errors once a minute after a node reports an error.

backend/agent/src/MoShiro.Agent/AgentApp.cs

@@ -28,7 +28,7 @@ public sealed class AgentApp : IDisposable, IAsyncDisposable
     private readonly LoadedNodeIdentity _identity;
     private readonly TimeProvider _time;
     private readonly INodeLog _log;
-    private readonly INodeLogBatchSource? _logBatchSource;
+    private readonly INodeLogSource? _logSource;
     private readonly MonoClock _clock;
     private readonly AgentCounters _counters = new();
     private readonly SessionRegistry _sessions = new();
@@ -62,7 +62,7 @@ public sealed class AgentApp : IDisposable, IAsyncDisposable
         _identity = identity;
         _time = time;
         _log = log;
-        _logBatchSource = log as INodeLogBatchSource;
+        _logSource = log as INodeLogSource;
         _clock = new MonoClock(time);
         _uplink = new BackendUplink(time);
 
@@ -320,6 +320,23 @@ public sealed class AgentApp : IDisposable, IAsyncDisposable
                 async (_, request, _) => Result<TestRunResult>.Ok(new TestRunResult { Accepted = await _hub.DisconnectAsync(request.DialerId.Value) }));
         }
 
+        if (Allow(MoShiroMethods.LogsFetch))
+        {
+            router.On(
+                MoShiroMethods.LogsFetch,
+                MoShiroJsonContext.Default.LogsFetchParams,
+                MoShiroJsonContext.Default.LogsFetchResult,
+                (_, request, _) =>
+                {
+                    NodeLogPage page = _logSource?.Read(request.AfterId, request.Limit, request.MinLevel) ?? new NodeLogPage([], 0);
+                    return ValueTask.FromResult(Result<LogsFetchResult>.Ok(new LogsFetchResult
+                    {
+                        LastId = page.LastId,
+                        Items = [.. page.Items.Select(e => new LogEntryDto { Id = e.Id, Type = e.Type, AtUtcMs = e.Record.AtUtcMs, Level = e.Record.Level, Message = e.Record.Message, Fields = e.Record.Fields })],
+                    }));
+                });
+        }
+
         if (Allow(MoShiroMethods.LinkRetry))
         {
             router.OnNotify(MoShiroMethods.LinkRetry, MoShiroJsonContext.Default.LinkRetryParams, (_, request, _) =>
@@ -407,7 +424,7 @@ public sealed class AgentApp : IDisposable, IAsyncDisposable
         long seconds = Math.Max(1, (nowMs - _lastAtMs) / 1000);
         long packetsIn = _counters.PacketsIn;
         long packetsOut = _counters.PacketsOut;
-        NodeLogBatch logBatch = _logBatchSource?.TakeBatch(16) ?? new NodeLogBatch([], 0);
+        NodeLogSummary? logSummary = _logSource?.TakeSummary();
         UpdateStatus? updateStatus = _nativeUpdate?.Status() ?? _update?.Status();
         var extra = new NodeHeartbeatExtra
         {
@@ -421,8 +438,14 @@ public sealed class AgentApp : IDisposable, IAsyncDisposable
             DroppedRateLimited = _counters.DroppedRateLimited,
             QueueBytes = _outbox.PendingBytes,
             Update = updateStatus,
-            RuntimeLogs = logBatch.Records.Count == 0 ? null : [.. logBatch.Records],
-            DroppedRuntimeLogs = logBatch.Dropped == 0 ? null : logBatch.Dropped,
+            LogSummary = logSummary is null ? null : new LogSummaryDto
+            {
+                LastId = logSummary.LastId,
+                Info = logSummary.Info,
+                Warn = logSummary.Warn,
+                Error = logSummary.Error,
+                Types = [.. logSummary.Types.Select(t => new LogTypeCountDto { Type = t.Type, Level = t.Level, Count = t.Count })],
+            },
         };
         _lastIn = packetsIn;
         _lastOut = packetsOut;