Reduce idle CPU across 62 containers (phase 1)

- Add resource limits (heavy/medium/light tiers) to all 59 .NET services
- Add .NET GC tuning (server/workstation GC, DATAS, conserve memory)
- Convert FirstSignalSnapshotWriter from 10s polling to Valkey pub/sub
- Convert EnvironmentSettingsRefreshService from 60s polling to Valkey pub/sub
- Consolidate GraphAnalytics dual timers to single timer with idle-skip
- Increase healthcheck interval from 30s to 60s (configurable)
- Reduce debug logging to Information on 4 high-traffic services

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Graph/StellaOps.Graph.Indexer/Analytics/GraphAnalyticsHostedService.cs

@@ -8,37 +8,49 @@ namespace StellaOps.Graph.Indexer.Analytics;
 public sealed class GraphAnalyticsHostedService : BackgroundService
 {
     private readonly IGraphAnalyticsPipeline _pipeline;
+    private readonly IGraphSnapshotProvider _snapshotProvider;
     private readonly GraphAnalyticsOptions _options;
     private readonly ILogger<GraphAnalyticsHostedService> _logger;
 
     public GraphAnalyticsHostedService(
         IGraphAnalyticsPipeline pipeline,
+        IGraphSnapshotProvider snapshotProvider,
         IOptions<GraphAnalyticsOptions> options,
         ILogger<GraphAnalyticsHostedService> logger)
     {
         _pipeline = pipeline ?? throw new ArgumentNullException(nameof(pipeline));
+        _snapshotProvider = snapshotProvider ?? throw new ArgumentNullException(nameof(snapshotProvider));
         _options = options?.Value ?? throw new ArgumentNullException(nameof(options));
         _logger = logger ?? throw new ArgumentNullException(nameof(logger));
     }
 
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {
-        using var clusteringTimer = new PeriodicTimer(_options.ClusterInterval);
-        using var centralityTimer = new PeriodicTimer(_options.CentralityInterval);
+        var interval = _options.ClusterInterval < _options.CentralityInterval
+            ? _options.ClusterInterval
+            : _options.CentralityInterval;
+
+        using var timer = new PeriodicTimer(interval);
 
         while (!stoppingToken.IsCancellationRequested)
         {
-            var clusteringTask = clusteringTimer.WaitForNextTickAsync(stoppingToken).AsTask();
-            var centralityTask = centralityTimer.WaitForNextTickAsync(stoppingToken).AsTask();
-
-            var completed = await Task.WhenAny(clusteringTask, centralityTask).ConfigureAwait(false);
-            if (completed.IsCanceled || stoppingToken.IsCancellationRequested)
+            if (!await timer.WaitForNextTickAsync(stoppingToken).ConfigureAwait(false))
             {
                 break;
             }
 
             try
             {
+                if (_options.SkipWhenIdle)
+                {
+                    var pending = await _snapshotProvider.GetPendingSnapshotsAsync(stoppingToken).ConfigureAwait(false);
+                    if (pending.Count == 0)
+                    {
+                        _logger.LogDebug("graph-indexer: skipping analytics pipeline, no pending snapshots");
+                        continue;
+                    }
+                }
+
                 await _pipeline.RunAsync(new GraphAnalyticsRunContext(ForceBackfill: false), stoppingToken).ConfigureAwait(false);
             }
             catch (OperationCanceledException)

src/Graph/StellaOps.Graph.Indexer/Analytics/GraphAnalyticsOptions.cs

@@ -28,4 +28,9 @@ public sealed class GraphAnalyticsOptions
     /// Whether to also write cluster ids onto graph node documents (alongside overlays).
     /// </summary>
     public bool WriteClusterAssignmentsToNodes { get; set; } = true;
+
+    /// <summary>
+    /// When true, skips the analytics pipeline if no pending snapshots exist.
+    /// </summary>
+    public bool SkipWhenIdle { get; set; } = true;
 }