Fix chart zero lines, collection log server name, and overview online status (#85, #91, #93)

#85: Blocking/deadlock trend charts now show a visible flat line at zero
instead of empty space. Added negative Y-axis margin so zero-value data
renders above the axis border. Reduced fallback Y range from +100 to +1.

#91: Added server_name column to collection_log DuckDB table (schema v10)
so log entries identify which server produced them without a lookup join.

#93: Sidebar status dots now reflect actual connection check results
(IsOnline) instead of the IsEnabled user config toggle. Added IsOnline
property to ServerConnection model, synced from connection status in
RefreshServerList and CheckConnectionsAndNotify. Fixed first-check
refresh so dots update as soon as initial connection checks complete.

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

Author: erikdarlingdata

Lite/Controls/ServerTab.xaml.cs

@@ -849,12 +849,19 @@ private void UpdateBlockingTrendChart(List<TrendPoint> data, int hoursBack, Date
 
         if (data.Count == 0)
         {
-            /* Show empty chart with correct time range */
+            /* No blocking events — show a flat line at zero so the chart looks active */
+            var zeroLine = BlockingTrendChart.Plot.Add.Scatter(
+                new[] { rangeStart.ToOADate(), rangeEnd.ToOADate() },
+                new[] { 0.0, 0.0 });
+            zeroLine.LegendText = "Blocking Incidents";
+            zeroLine.Color = ScottPlot.Color.FromHex("#E57373");
+            zeroLine.MarkerSize = 0;
             BlockingTrendChart.Plot.Axes.DateTimeTicksBottom();
             BlockingTrendChart.Plot.Axes.SetLimitsX(rangeStart.ToOADate(), rangeEnd.ToOADate());
-            BlockingTrendChart.Plot.Axes.SetLimitsY(0, 1);
             ReapplyAxisColors(BlockingTrendChart);
             BlockingTrendChart.Plot.YLabel("Blocking Incidents");
+            SetChartYLimitsWithLegendPadding(BlockingTrendChart, 0, 1);
+            ShowChartLegend(BlockingTrendChart);
             BlockingTrendChart.Refresh();
             return;
         }
@@ -919,12 +926,19 @@ private void UpdateDeadlockTrendChart(List<TrendPoint> data, int hoursBack, Date
 
         if (data.Count == 0)
         {
-            /* Show empty chart with correct time range */
+            /* No deadlocks — show a flat line at zero so the chart looks active */
+            var zeroLine = DeadlockTrendChart.Plot.Add.Scatter(
+                new[] { rangeStart.ToOADate(), rangeEnd.ToOADate() },
+                new[] { 0.0, 0.0 });
+            zeroLine.LegendText = "Deadlocks";
+            zeroLine.Color = ScottPlot.Color.FromHex("#FFB74D");
+            zeroLine.MarkerSize = 0;
             DeadlockTrendChart.Plot.Axes.DateTimeTicksBottom();
             DeadlockTrendChart.Plot.Axes.SetLimitsX(rangeStart.ToOADate(), rangeEnd.ToOADate());
-            DeadlockTrendChart.Plot.Axes.SetLimitsY(0, 1);
             ReapplyAxisColors(DeadlockTrendChart);
             DeadlockTrendChart.Plot.YLabel("Deadlocks");
+            SetChartYLimitsWithLegendPadding(DeadlockTrendChart, 0, 1);
+            ShowChartLegend(DeadlockTrendChart);
             DeadlockTrendChart.Refresh();
             return;
         }
@@ -1495,13 +1509,13 @@ private static void SetChartYLimitsWithLegendPadding(ScottPlot.WPF.WpfPlot chart
             dataYMin = limits.Bottom;
             dataYMax = limits.Top;
         }
-        if (dataYMax <= dataYMin) dataYMax = dataYMin + 100;
+        if (dataYMax <= dataYMin) dataYMax = dataYMin + 1;
 
         double range = dataYMax - dataYMin;
         double topPadding = range * 0.05;
 
-        /* Only add bottom padding if dataYMin is above zero - don't go negative */
-        double yMin = dataYMin >= 0 ? 0 : dataYMin - (range * 0.10);
+        /* Add small bottom margin when dataYMin is zero so flat lines at Y=0 are visible above the axis */
+        double yMin = dataYMin > 0 ? 0 : dataYMin == 0 ? -(range * 0.05) : dataYMin - (range * 0.10);
         double yMax = dataYMax + topPadding;
 
         chart.Plot.Axes.SetLimitsY(yMin, yMax);

Lite/Database/DuckDbInitializer.cs

@@ -19,7 +19,7 @@ public class DuckDbInitializer
     /// <summary>
     /// Current schema version. Increment this when schema changes require table rebuilds.
     /// </summary>
-    private const int CurrentSchemaVersion = 9;
+    private const int CurrentSchemaVersion = 10;
 
     public DuckDbInitializer(string databasePath, ILogger<DuckDbInitializer>? logger = null)
     {
@@ -328,6 +328,21 @@ Safe to ALTER because this table uses INSERT (not appender). */
                 /* Table doesn't exist yet — will be created with correct schema below */
             }
         }
+
+        if (fromVersion < 10)
+        {
+            /* v10: Added server_name column to collection_log so log entries
+                    can be identified by server without needing a lookup table. */
+            _logger?.LogInformation("Running migration to v10: adding server_name column to collection_log");
+            try
+            {
+                await ExecuteNonQueryAsync(connection, "ALTER TABLE collection_log ADD COLUMN IF NOT EXISTS server_name VARCHAR");
+            }
+            catch
+            {
+                /* Table doesn't exist yet — will be created with correct schema below */
+            }
+        }
     }
 
     /// <summary>

Lite/Database/Schema.cs

@@ -38,6 +38,7 @@ modified_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP
 CREATE TABLE IF NOT EXISTS collection_log (
     log_id BIGINT PRIMARY KEY,
     server_id INTEGER NOT NULL,
+    server_name VARCHAR,
     collector_name VARCHAR NOT NULL,
     collection_time TIMESTAMP NOT NULL,
     duration_ms INTEGER,

Lite/MainWindow.xaml

@@ -97,10 +97,10 @@
                                             <Style TargetType="Ellipse">
                                                 <Setter Property="Fill" Value="{DynamicResource ForegroundMutedBrush}"/>
                                                 <Style.Triggers>
-                                                    <DataTrigger Binding="{Binding IsEnabled}" Value="True">
+                                                    <DataTrigger Binding="{Binding IsOnline}" Value="True">
                                                         <Setter Property="Fill" Value="{DynamicResource SuccessBrush}"/>
                                                     </DataTrigger>
-                                                    <DataTrigger Binding="{Binding IsEnabled}" Value="False">
+                                                    <DataTrigger Binding="{Binding IsOnline}" Value="False">
                                                         <Setter Property="Fill" Value="{DynamicResource ErrorBrush}"/>
                                                     </DataTrigger>
                                                 </Style.Triggers>

Lite/MainWindow.xaml.cs

@@ -249,6 +249,10 @@ private void ServerTabControl_SelectionChanged(object sender, SelectionChangedEv
     private void RefreshServerList()
     {
         var servers = _serverManager.GetAllServers();
+        foreach (var server in servers)
+        {
+            server.IsOnline = _serverManager.GetConnectionStatus(server.Id).IsOnline;
+        }
         ServerListView.ItemsSource = servers;
 
         // Update UI based on server count
@@ -883,9 +887,11 @@ private void CheckConnectionsAndNotify()
         try
         {
             var servers = _serverManager.GetAllServers();
+            bool needsRefresh = false;
             foreach (var server in servers)
             {
                 var status = _serverManager.GetConnectionStatus(server.Id);
+                server.IsOnline = status?.IsOnline;
                 if (status?.IsOnline == null) continue;
 
                 bool isOnline = status.IsOnline == true;
@@ -912,12 +918,22 @@ private void CheckConnectionsAndNotify()
 
                     if (wasOnline != isOnline)
                     {
-                        RefreshServerList();
+                        needsRefresh = true;
                     }
                 }
+                else
+                {
+                    /* First time seeing this server's status — need to refresh */
+                    needsRefresh = true;
+                }
 
                 _previousConnectionStates[server.Id] = isOnline;
             }
+
+            if (needsRefresh)
+            {
+                RefreshServerList();
+            }
         }
         catch (Exception ex)
         {

Lite/Models/ServerConnection.cs

@@ -81,6 +81,13 @@ public bool UseWindowsAuth
         _ => "Windows"
     };
 
+    /// <summary>
+    /// Actual connection status from the most recent connection check.
+    /// null = not checked yet, true = online, false = offline.
+    /// </summary>
+    [JsonIgnore]
+    public bool? IsOnline { get; set; }
+
     /// <summary>
     /// Display-only property for showing status in UI.
     /// </summary>

Lite/Services/LocalDataService.CollectionHealth.cs

@@ -79,7 +79,8 @@ public async Task<List<CollectionLogRow>> GetRecentCollectionLogAsync(int server
     duckdb_duration_ms,
     rows_collected,
     status,
-    error_message
+    error_message,
+    server_name
 FROM collection_log
 WHERE server_id = $1
 AND   collection_time >= $2
@@ -103,7 +104,8 @@ ORDER BY collection_time DESC
                 DuckDbDurationMs = reader.IsDBNull(4) ? null : (int?)Convert.ToInt32(reader.GetValue(4)),
                 RowsCollected = reader.IsDBNull(5) ? null : (int?)Convert.ToInt32(reader.GetValue(5)),
                 Status = reader.GetString(6),
-                ErrorMessage = reader.IsDBNull(7) ? null : reader.GetString(7)
+                ErrorMessage = reader.IsDBNull(7) ? null : reader.GetString(7),
+                ServerName = reader.IsDBNull(8) ? null : reader.GetString(8)
             });
         }
 
@@ -114,6 +116,7 @@ ORDER BY collection_time DESC
 public class CollectionLogRow
 {
     public string CollectorName { get; set; } = "";
+    public string? ServerName { get; set; }
     public DateTime CollectionTime { get; set; }
     public int? DurationMs { get; set; }
     public int? SqlDurationMs { get; set; }

Lite/Services/RemoteCollectorService.cs

@@ -363,13 +363,13 @@ public async Task RunCollectorAsync(ServerConnection server, string collectorNam
         RecordCollectorResult(GetServerId(server), collectorName, status == "SUCCESS", errorMessage);
 
         // Log the collection attempt
-        await LogCollectionAsync(GetServerId(server), collectorName, startTime, status, errorMessage, rowsCollected, _lastSqlMs, _lastDuckDbMs);
+        await LogCollectionAsync(GetServerId(server), server.DisplayName, collectorName, startTime, status, errorMessage, rowsCollected, _lastSqlMs, _lastDuckDbMs);
     }
 
     /// <summary>
     /// Logs a collection attempt to the collection_log table.
     /// </summary>
-    private async Task LogCollectionAsync(int serverId, string collectorName, DateTime startTime, string status, string? errorMessage, int rowsCollected, long sqlMs = 0, long duckDbMs = 0)
+    private async Task LogCollectionAsync(int serverId, string serverName, string collectorName, DateTime startTime, string status, string? errorMessage, int rowsCollected, long sqlMs = 0, long duckDbMs = 0)
     {
         try
         {
@@ -380,11 +380,12 @@ private async Task LogCollectionAsync(int serverId, string collectorName, DateTi
 
             using var command = connection.CreateCommand();
             command.CommandText = @"
-                INSERT INTO collection_log (log_id, server_id, collector_name, collection_time, duration_ms, status, error_message, rows_collected, sql_duration_ms, duckdb_duration_ms)
-                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)";
+                INSERT INTO collection_log (log_id, server_id, server_name, collector_name, collection_time, duration_ms, status, error_message, rows_collected, sql_duration_ms, duckdb_duration_ms)
+                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)";
 
             command.Parameters.Add(new DuckDBParameter { Value = GenerateCollectionId() });
             command.Parameters.Add(new DuckDBParameter { Value = serverId });
+            command.Parameters.Add(new DuckDBParameter { Value = serverName });
             command.Parameters.Add(new DuckDBParameter { Value = collectorName });
             command.Parameters.Add(new DuckDBParameter { Value = startTime });
             command.Parameters.Add(new DuckDBParameter { Value = durationMs });