Limit health timeline to the latest 100 observations

HealthMonitoring/HealthMonitoring.Tests/Reporting/DashboardModelsTests.cs

@@ -21,4 +21,32 @@ public void ServiceDashboardRow_preserves_registered_version()
 
         Assert.Equal("2.4.1", row.Version);
     }
+
+    [Fact]
+    public void TimelineObservationSelector_returns_latest_100_in_display_order()
+    {
+        var observations = Enumerable.Range(0, 101)
+            .Select(index => new HealthObservation
+            {
+                ObservedAtUtc = DateTimeOffset.UtcNow.AddMinutes(index),
+                Status = HealthStatus.Healthy
+            })
+            .ToArray();
+
+        var selected = TimelineObservationSelector.Select(observations).ToArray();
+
+        Assert.Equal(100, selected.Length);
+        Assert.Equal(observations[1].ObservedAtUtc, selected[0].ObservedAtUtc);
+        Assert.Equal(observations[100].ObservedAtUtc, selected[^1].ObservedAtUtc);
+    }
+
+    [Fact]
+    public void TimelineObservationSelector_exposes_maximum_segments_as_read_only_property()
+    {
+        var property = typeof(TimelineObservationSelector).GetProperty(nameof(TimelineObservationSelector.MaximumSegments));
+
+        Assert.NotNull(property);
+        Assert.False(property!.CanWrite);
+        Assert.Equal(100, property.GetValue(null));
+    }
 }

HealthMonitoring/HealthMonitoring/Components/Pages/ServiceDetail.razor

@@ -11,7 +11,7 @@ else
 <div class="page-heading"><div><p class="eyebrow">SERVICE DETAIL · @_model.Service.Environment</p><h1>@_model.Service.Name</h1><p class="muted">@MonitorDescription</p><p class="service-version-detail">Version: <strong>@(string.IsNullOrWhiteSpace(_model.Service.Version) ? "not reported" : _model.Service.Version)</strong></p></div><div><a class="button secondary" href="@($"/services/{ServiceId}/dependencies")">Manage dependency links</a> <a class="button secondary" href="/">Back to overview</a></div></div>
     <div class="detail-status"><StatusBadge Status="@_model.Summary.Status" /> <span>Last checked @( _model.Summary.LastChecked?.ToLocalTime().ToString("dd MMM, HH:mm:ss") ?? "never")</span></div>
     <div class="stat-grid three"><StatCard Label="Uptime (24 hours)" Value="@UptimeText" Class="healthy" /><StatCard Label="Observations" Value="@_model.Observations.Count" Class="neutral" /><StatCard Label="Response" Value="@ResponseText" Class="neutral" /></div>
-    <section class="panel"><h2>Status timeline</h2><div class="timeline">@foreach (var observation in _model.Observations.OrderBy(item => item.ObservedAtUtc)) { <span class="timeline-segment @observation.Status.ToString().ToLowerInvariant()" title="@observation.ObservedAtUtc.ToLocalTime()"></span> }</div></section>
+    <section class="panel"><h2>Status timeline</h2><div class="timeline">@foreach (var observation in TimelineObservationSelector.Select(_model.Observations)) { <span class="timeline-segment @observation.Status.ToString().ToLowerInvariant()" title="@observation.ObservedAtUtc.ToLocalTime()"></span> }</div></section>
     <section class="panel"><h2>Dependency details</h2>@if (_model.Checks.Count == 0) { <p class="muted">No dependency details have been returned.</p> } else { <div class="check-table"><div class="table-heading"><span>Check</span><span>Status</span><span>Duration</span><span>Details</span></div>@foreach (var check in LatestChecks) { var link = _model.DependencyLinks.FirstOrDefault(item => string.Equals(item.DependencyName.Trim(), check.Result.Name.Trim(), StringComparison.OrdinalIgnoreCase)); <div class="service-row"><div>@if (link is null) { <strong>@check.Result.Name</strong> } else { <a class="dependency-link" href="@($"/services/{link.TargetServiceId}")"><strong>@check.Result.Name</strong> ↗</a> }</div><div><StatusBadge Status="@check.Result.Status" /></div><div>@check.Result.Duration.TotalMilliseconds.ToString("0") ms</div><div>@(check.Result.Description ?? check.Result.Exception ?? "No detail")</div></div>}</div> }</section>
     <details class="panel raw"><summary>Latest raw health response</summary><pre>@(_model.Observations.FirstOrDefault()?.RawResponseJson ?? "No response recorded.")</pre></details>
 }

HealthMonitoring/HealthMonitoring/Reporting/TimelineObservationSelector.cs

@@ -0,0 +1,13 @@
+using HealthMonitoring.Domain;
+
+namespace HealthMonitoring.Reporting;
+
+public static class TimelineObservationSelector
+{
+    public static int MaximumSegments => 100;
+
+    public static IEnumerable<HealthObservation> Select(IEnumerable<HealthObservation> observations) => observations
+        .OrderByDescending(observation => observation.ObservedAtUtc)
+        .Take(MaximumSegments)
+        .OrderBy(observation => observation.ObservedAtUtc);
+}