Address review feedback: skip channel allocation when no filter, remove Task.Delay from tests

Author: JamesNK

src/Aspire.Dashboard/Api/TelemetryApiService.cs

@@ -46,9 +46,9 @@ internal sealed class TelemetryApiService(
         var spanFilters = new List<TelemetryFilter>();
         var searchTextFragments = ParseAndApplySearchFilters(search, spanFilters, AddSpanFiltersFromQualifiers, key => ResolveSpanFieldKey(key) is not null);
 
-        // Get spans for all resource keys
+        // Get spans for all resource keys (empty list means no filter / all resources)
         var allSpans = new List<OtlpSpan>();
-        foreach (var resourceKey in resourceKeys)
+        foreach (var resourceKey in resourceKeys.Count > 0 ? resourceKeys.Select(k => (ResourceKey?)k) : [null])
         {
             var result = telemetryRepository.GetSpans(new GetSpansRequest
             {
@@ -103,9 +103,9 @@ internal sealed class TelemetryApiService(
         var traceFilters = new List<TelemetryFilter>();
         var searchTextFragments = ParseAndApplySearchFilters(search, traceFilters, AddSpanFiltersFromQualifiers, key => ResolveSpanFieldKey(key) is not null);
 
-        // Get traces for all resource keys
+        // Get traces for all resource keys (empty list means no filter / all resources)
         var allTraces = new List<OtlpTrace>();
-        foreach (var resourceKey in resourceKeys)
+        foreach (var resourceKey in resourceKeys.Count > 0 ? resourceKeys.Select(k => (ResourceKey?)k) : [null])
         {
             var result = telemetryRepository.GetTraces(new GetTracesRequest
             {
@@ -222,8 +222,9 @@ internal sealed class TelemetryApiService(
         var searchTextFragments = ParseAndApplySearchFilters(search, filters, AddLogFiltersFromQualifiers, key => ResolveLogFieldKey(key) is not null);
 
         // Get logs for all resource keys
+        // Get logs for all resource keys (empty list means no filter / all resources)
         var allLogs = new List<OtlpLogEntry>();
-        foreach (var resourceKey in resourceKeys)
+        foreach (var resourceKey in resourceKeys.Count > 0 ? resourceKeys.Select(k => (ResourceKey?)k) : [null])
         {
             var result = telemetryRepository.GetLogs(new GetLogsContext
             {
@@ -278,7 +279,7 @@ public async IAsyncEnumerable<string> FollowSpansAsync(
         // Build the watch request with all filters pushed into the repository
         var watchRequest = new WatchSpansRequest
         {
-            ResourceKey = resourceKeys is { Count: 1 } ? resourceKeys[0] : null,
+            ResourceKey = resourceKeys is [var singleKey] ? singleKey : null,
             Filters = spanFilters,
             TraceId = traceId,
             HasError = hasError,
@@ -291,7 +292,7 @@ public async IAsyncEnumerable<string> FollowSpansAsync(
             // Multi-resource filtering: repository only supports single ResourceKey,
             // so for multi-resource queries we filter here.
             if (resourceKeys is { Count: > 1 } &&
-                !resourceKeys.Any(k => k?.EqualsCompositeName(span.Source.ResourceKey.GetCompositeName()) == true))
+                !resourceKeys.Any(k => k.EqualsCompositeName(span.Source.ResourceKey.GetCompositeName())))
             {
                 continue;
             }
@@ -348,7 +349,7 @@ public async IAsyncEnumerable<string> FollowLogsAsync(
         // Build the watch request with all filters pushed into the repository
         var watchRequest = new WatchLogsRequest
         {
-            ResourceKey = resourceKeys is { Count: 1 } ? resourceKeys[0] : null,
+            ResourceKey = resourceKeys is [var singleKey] ? singleKey : null,
             Filters = filters,
             TextFragments = searchTextFragments
         };
@@ -359,7 +360,7 @@ public async IAsyncEnumerable<string> FollowLogsAsync(
             // Multi-resource filtering: repository only supports single ResourceKey,
             // so for multi-resource queries we filter here.
             if (resourceKeys is { Count: > 1 } &&
-                !resourceKeys.Any(k => k?.EqualsCompositeName(log.ResourceView.ResourceKey.GetCompositeName()) == true))
+                !resourceKeys.Any(k => k.EqualsCompositeName(log.ResourceView.ResourceKey.GetCompositeName())))
             {
                 continue;
             }
@@ -551,8 +552,14 @@ private static void AddSpanFiltersFromQualifiers(SearchFilter parsedSearch, List
     /// to pick up data once the resource is first seen.
     /// Throws OperationCanceledException if cancellation is triggered before the resources appear.
     /// </summary>
-    private async Task<List<ResourceKey?>> WaitForResourceKeysAsync(string[]? resourceNames, CancellationToken cancellationToken)
+    private async Task<List<ResourceKey>> WaitForResourceKeysAsync(string[]? resourceNames, CancellationToken cancellationToken)
     {
+        if (resourceNames is null || resourceNames.Length == 0)
+        {
+            // No filter - return immediately without allocating a channel or subscription.
+            return [];
+        }
+
         // Subscribe before the first check so no notification can be missed between
         // GetResources() and the subscription registration.
         var signal = Channel.CreateBounded<bool>(new BoundedChannelOptions(1) { FullMode = BoundedChannelFullMode.DropOldest });
@@ -577,24 +584,23 @@ private static void AddSpanFiltersFromQualifiers(SearchFilter parsedSearch, List
     /// <summary>
     /// Resolves resource names to ResourceKeys.
     /// Returns null if any specified resource is not found.
-    /// If no resources are specified, returns a list with a single null key (no filter).
+    /// Returns an empty list when no resource filter is specified (meaning all resources).
     /// </summary>
-    private static List<ResourceKey?>? ResolveResourceKeys(IReadOnlyList<OtlpResource> resources, string[]? resourceNames)
+    private static List<ResourceKey>? ResolveResourceKeys(IReadOnlyList<OtlpResource> resources, string[]? resourceNames)
     {
         if (resourceNames is null || resourceNames.Length == 0)
         {
-            // No filter - return a list with null to indicate "all resources"
-            return [null];
+            return [];
         }
 
-        var keys = new List<ResourceKey?>();
+        var keys = new List<ResourceKey>();
         foreach (var resourceName in resourceNames)
         {
             if (!AIHelpers.TryResolveResourceForTelemetry(resources, resourceName, out _, out var resourceKey))
             {
                 return null;
             }
-            keys.Add(resourceKey);
+            keys.Add(resourceKey!.Value);
         }
         return keys;
     }

tests/Aspire.Dashboard.Tests/TelemetryApiServiceTests.cs

@@ -652,30 +652,20 @@ public async Task FollowSpansAsync_WaitsForResourceToAppear_ThenStreams()
         var service = CreateService(repository);
         using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
 
-        var receivedItems = new List<string>();
-
-        // Start streaming for a resource that doesn't exist yet.
-        var streamTask = Task.Run(async () =>
-        {
-            await foreach (var item in service.FollowSpansAsync(["service1"], null, null, null, cancellationToken: cts.Token))
-            {
-                receivedItems.Add(item);
-                if (receivedItems.Count >= 1)
-                {
-                    break;
-                }
-            }
-        }, cts.Token);
+        // Start enumerating - MoveNextAsync will block until data arrives.
+        var enumerator = service.FollowSpansAsync(["service1"], null, null, null, cancellationToken: cts.Token).GetAsyncEnumerator(cts.Token);
+        var moveNextTask = enumerator.MoveNextAsync();
 
-        // Give the streaming task time to start waiting for the resource.
-        await Task.Delay(100, cts.Token);
+        // The task should not complete yet because the resource doesn't exist.
+        Assert.False(moveNextTask.IsCompleted);
 
         // Now add spans for the resource - this should unblock the stream.
         AddSpans(repository, count: 1);
 
-        await streamTask;
+        Assert.True(await moveNextTask);
+        Assert.NotNull(enumerator.Current);
 
-        Assert.Single(receivedItems);
+        await enumerator.DisposeAsync();
     }
 
     [Fact]
@@ -685,30 +675,20 @@ public async Task FollowLogsAsync_WaitsForResourceToAppear_ThenStreams()
         var service = CreateService(repository);
         using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
 
-        var receivedItems = new List<string>();
-
-        // Start streaming for a resource that doesn't exist yet.
-        var streamTask = Task.Run(async () =>
-        {
-            await foreach (var item in service.FollowLogsAsync(["service1"], null, null, null, cts.Token))
-            {
-                receivedItems.Add(item);
-                if (receivedItems.Count >= 1)
-                {
-                    break;
-                }
-            }
-        }, cts.Token);
+        // Start enumerating - MoveNextAsync will block until data arrives.
+        var enumerator = service.FollowLogsAsync(["service1"], null, null, null, cts.Token).GetAsyncEnumerator(cts.Token);
+        var moveNextTask = enumerator.MoveNextAsync();
 
-        // Give the streaming task time to start waiting for the resource.
-        await Task.Delay(100, cts.Token);
+        // The task should not complete yet because the resource doesn't exist.
+        Assert.False(moveNextTask.IsCompleted);
 
         // Now add logs for the resource - this should unblock the stream.
         AddLogs(repository, ["hello"]);
 
-        await streamTask;
+        Assert.True(await moveNextTask);
+        Assert.NotNull(enumerator.Current);
 
-        Assert.Single(receivedItems);
+        await enumerator.DisposeAsync();
     }
 
     // SpanId is serialized as lowercase hex per the OTLP/JSON spec