Merge branch 'main' into reyang/aspnetcore-logging-example

Author: reyang

docs/metrics/README.md

@@ -27,11 +27,15 @@ MyFruitCounter.Add(5, new("name", "apple"), new("color", "red"), new("taste", "s
 MyFruitCounter.Add(7, new("color", "red"), new("name", "apple"), new("taste", "sweet")); // <--- DON'T DO THIS
 ```
 
-- When emitting metrics with more than three tags, use `TagList` for better
-  performance. Using
+For the best performance, it is highly recommended to pass in tags in certain
+ways so allocations are only happening on the stack rather than the heap,
+which eliminates pressure on the GC (garbage collector):
+
+- When reporting measurements with 3 tags or less,
+  emit the tags individually.
+- When reporting measurements with more than 3 tags, use
   [`TagList`](https://learn.microsoft.com/dotnet/api/system.diagnostics.taglist?view=net-7.0#remarks)
-  avoids allocating any memory for up to eight tags, thereby, reducing the
-  pressure on GC to free up memory.
+  for better performance.
 
 ```csharp
 var tags = new TagList

src/OpenTelemetry/Metrics/AggregationType.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenTelemetry.Metrics;
 
 internal enum AggregationType

src/OpenTelemetry/Metrics/AggregatorStore.cs

@@ -14,7 +14,10 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Collections.Concurrent;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using OpenTelemetry.Internal;
 
@@ -23,11 +26,12 @@ namespace OpenTelemetry.Metrics;
 internal sealed class AggregatorStore
 {
     private static readonly string MetricPointCapHitFixMessage = "Consider opting in for the experimental SDK feature to emit all the throttled metrics under the overflow attribute by setting env variable OTEL_DOTNET_EXPERIMENTAL_METRICS_EMIT_OVERFLOW_ATTRIBUTE = true. You could also modify instrumentation to reduce the number of unique key/value pair combinations. Or use Views to drop unwanted tags. Or use MeterProviderBuilder.SetMaxMetricPointsPerMetricStream to set higher limit.";
-    private static readonly Comparison<KeyValuePair<string, object>> DimensionComparisonDelegate = (x, y) => x.Key.CompareTo(y.Key);
+    private static readonly Comparison<KeyValuePair<string, object?>> DimensionComparisonDelegate = (x, y) => x.Key.CompareTo(y.Key);
+    private static readonly ExemplarFilter DefaultExemplarFilter = new AlwaysOffExemplarFilter();
 
     private readonly object lockZeroTags = new();
     private readonly object lockOverflowTag = new();
-    private readonly HashSet<string> tagKeysInteresting;
+    private readonly HashSet<string>? tagKeysInteresting;
     private readonly int tagsKeysInterestingCount;
 
     private readonly ConcurrentDictionary<Tags, int> tagsToMetricPointIndexDictionary =
@@ -60,7 +64,7 @@ internal AggregatorStore(
         AggregationTemporality temporality,
         int maxMetricPoints,
         bool emitOverflowAttribute,
-        ExemplarFilter exemplarFilter = null)
+        ExemplarFilter? exemplarFilter = null)
     {
         this.name = metricStreamIdentity.InstrumentName;
         this.maxMetricPoints = maxMetricPoints;
@@ -73,7 +77,7 @@ internal AggregatorStore(
         this.exponentialHistogramMaxSize = metricStreamIdentity.ExponentialHistogramMaxSize;
         this.exponentialHistogramMaxScale = metricStreamIdentity.ExponentialHistogramMaxScale;
         this.StartTimeExclusive = DateTimeOffset.UtcNow;
-        this.exemplarFilter = exemplarFilter ?? new AlwaysOffExemplarFilter();
+        this.exemplarFilter = exemplarFilter ?? DefaultExemplarFilter;
         if (metricStreamIdentity.TagKeys == null)
         {
             this.updateLongCallback = this.UpdateLong;
@@ -98,9 +102,9 @@ internal AggregatorStore(
         }
     }
 
-    private delegate void UpdateLongDelegate(long value, ReadOnlySpan<KeyValuePair<string, object>> tags);
+    private delegate void UpdateLongDelegate(long value, ReadOnlySpan<KeyValuePair<string, object?>> tags);
 
-    private delegate void UpdateDoubleDelegate(double value, ReadOnlySpan<KeyValuePair<string, object>> tags);
+    private delegate void UpdateDoubleDelegate(double value, ReadOnlySpan<KeyValuePair<string, object?>> tags);
 
     internal DateTimeOffset StartTimeExclusive { get; private set; }
 
@@ -115,12 +119,12 @@ internal bool IsExemplarEnabled()
         return this.exemplarFilter is not AlwaysOffExemplarFilter;
     }
 
-    internal void Update(long value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    internal void Update(long value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         this.updateLongCallback(value, tags);
     }
 
-    internal void Update(double value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    internal void Update(double value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         this.updateDoubleCallback(value, tags);
     }
@@ -234,15 +238,15 @@ private void InitializeOverflowTagPointIfNotInitialized()
             {
                 if (!this.overflowTagMetricPointInitialized)
                 {
-                    this.metricPoints[1] = new MetricPoint(this, this.aggType, new KeyValuePair<string, object>[] { new("otel.metric.overflow", true) }, this.histogramBounds, this.exponentialHistogramMaxSize, this.exponentialHistogramMaxScale);
+                    this.metricPoints[1] = new MetricPoint(this, this.aggType, new KeyValuePair<string, object?>[] { new("otel.metric.overflow", true) }, this.histogramBounds, this.exponentialHistogramMaxSize, this.exponentialHistogramMaxScale);
                     this.overflowTagMetricPointInitialized = true;
                 }
             }
         }
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private int LookupAggregatorStore(KeyValuePair<string, object>[] tagKeysAndValues, int length)
+    private int LookupAggregatorStore(KeyValuePair<string, object?>[] tagKeysAndValues, int length)
     {
         var givenTags = new Tags(tagKeysAndValues);
 
@@ -275,10 +279,10 @@ private int LookupAggregatorStore(KeyValuePair<string, object>[] tagKeysAndValue
                     // so we need to make a deep copy for Dictionary storage.
                     if (length <= ThreadStaticStorage.MaxTagCacheSize)
                     {
-                        var givenTagKeysAndValues = new KeyValuePair<string, object>[length];
+                        var givenTagKeysAndValues = new KeyValuePair<string, object?>[length];
                         tagKeysAndValues.CopyTo(givenTagKeysAndValues.AsSpan());
 
-                        var sortedTagKeysAndValues = new KeyValuePair<string, object>[length];
+                        var sortedTagKeysAndValues = new KeyValuePair<string, object?>[length];
                         tempSortedTagKeysAndValues.CopyTo(sortedTagKeysAndValues.AsSpan());
 
                         givenTags = new Tags(givenTagKeysAndValues);
@@ -328,7 +332,7 @@ private int LookupAggregatorStore(KeyValuePair<string, object>[] tagKeysAndValue
                 }
 
                 // Note: We are using storage from ThreadStatic, so need to make a deep copy for Dictionary storage.
-                var givenTagKeysAndValues = new KeyValuePair<string, object>[length];
+                var givenTagKeysAndValues = new KeyValuePair<string, object?>[length];
 
                 tagKeysAndValues.CopyTo(givenTagKeysAndValues.AsSpan());
 
@@ -366,7 +370,7 @@ private int LookupAggregatorStore(KeyValuePair<string, object>[] tagKeysAndValue
         return aggregatorIndex;
     }
 
-    private void UpdateLong(long value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private void UpdateLong(long value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         try
         {
@@ -407,7 +411,7 @@ private void UpdateLong(long value, ReadOnlySpan<KeyValuePair<string, object>> t
         }
     }
 
-    private void UpdateLongCustomTags(long value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private void UpdateLongCustomTags(long value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         try
         {
@@ -448,7 +452,7 @@ private void UpdateLongCustomTags(long value, ReadOnlySpan<KeyValuePair<string,
         }
     }
 
-    private void UpdateDouble(double value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private void UpdateDouble(double value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         try
         {
@@ -489,7 +493,7 @@ private void UpdateDouble(double value, ReadOnlySpan<KeyValuePair<string, object
         }
     }
 
-    private void UpdateDoubleCustomTags(double value, ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private void UpdateDoubleCustomTags(double value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         try
         {
@@ -530,7 +534,7 @@ private void UpdateDoubleCustomTags(double value, ReadOnlySpan<KeyValuePair<stri
         }
     }
 
-    private int FindMetricAggregatorsDefault(ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private int FindMetricAggregatorsDefault(ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         int tagLength = tags.Length;
         if (tagLength == 0)
@@ -546,7 +550,7 @@ private int FindMetricAggregatorsDefault(ReadOnlySpan<KeyValuePair<string, objec
         return this.LookupAggregatorStore(tagKeysAndValues, tagLength);
     }
 
-    private int FindMetricAggregatorsCustomTag(ReadOnlySpan<KeyValuePair<string, object>> tags)
+    private int FindMetricAggregatorsCustomTag(ReadOnlySpan<KeyValuePair<string, object?>> tags)
     {
         int tagLength = tags.Length;
         if (tagLength == 0 || this.tagsKeysInterestingCount == 0)
@@ -555,12 +559,11 @@ private int FindMetricAggregatorsCustomTag(ReadOnlySpan<KeyValuePair<string, obj
             return 0;
         }
 
-        // TODO: Get only interesting tags
-        // from the incoming tags
-
         var storage = ThreadStaticStorage.GetStorage();
 
-        storage.SplitToKeysAndValues(tags, tagLength, this.tagKeysInteresting, out var tagKeysAndValues, out var actualLength);
+        Debug.Assert(this.tagKeysInteresting != null, "this.tagKeysInteresting was null");
+
+        storage.SplitToKeysAndValues(tags, tagLength, this.tagKeysInteresting!, out var tagKeysAndValues, out var actualLength);
 
         // Actual number of tags depend on how many
         // of the incoming tags has user opted to
@@ -571,6 +574,8 @@ private int FindMetricAggregatorsCustomTag(ReadOnlySpan<KeyValuePair<string, obj
             return 0;
         }
 
-        return this.LookupAggregatorStore(tagKeysAndValues, actualLength);
+        Debug.Assert(tagKeysAndValues != null, "tagKeysAndValues was null");
+
+        return this.LookupAggregatorStore(tagKeysAndValues!, actualLength);
     }
 }

src/OpenTelemetry/Metrics/Base2ExponentialBucketHistogram.LowerBoundary.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenTelemetry.Metrics;
 
 /// <content>

src/OpenTelemetry/Metrics/Base2ExponentialBucketHistogram.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
 using OpenTelemetry.Internal;
 
@@ -38,7 +40,7 @@ internal sealed partial class Base2ExponentialBucketHistogram
 
     internal int IsCriticalSectionOccupied = 0;
 
-    internal ExponentialHistogramData SnapshotExponentialHistogramData = new ExponentialHistogramData();
+    internal ExponentialHistogramData SnapshotExponentialHistogramData = new();
 
     private int scale;
     private double scalingFactor; // 2 ^ scale / log(2)
@@ -237,11 +239,13 @@ internal ExponentialHistogramData GetExponentialHistogramData()
     internal Base2ExponentialBucketHistogram Copy()
     {
         Debug.Assert(this.PositiveBuckets.Capacity == this.NegativeBuckets.Capacity, "Capacity of positive and negative buckets are not equal.");
-        var copy = new Base2ExponentialBucketHistogram(this.PositiveBuckets.Capacity, this.SnapshotExponentialHistogramData.Scale);
-        copy.SnapshotSum = this.SnapshotSum;
-        copy.SnapshotMin = this.SnapshotMin;
-        copy.SnapshotMax = this.SnapshotMax;
-        copy.SnapshotExponentialHistogramData = this.SnapshotExponentialHistogramData.Copy();
-        return copy;
+
+        return new Base2ExponentialBucketHistogram(this.PositiveBuckets.Capacity, this.SnapshotExponentialHistogramData.Scale)
+        {
+            SnapshotSum = this.SnapshotSum,
+            SnapshotMin = this.SnapshotMin,
+            SnapshotMax = this.SnapshotMax,
+            SnapshotExponentialHistogramData = this.SnapshotExponentialHistogramData.Copy(),
+        };
     }
 }

src/OpenTelemetry/Metrics/Base2ExponentialBucketHistogramConfiguration.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenTelemetry.Metrics;
 
 /// <summary>

src/OpenTelemetry/Metrics/CircularBufferBuckets.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using OpenTelemetry.Internal;
@@ -25,7 +27,7 @@ namespace OpenTelemetry.Metrics;
 /// </summary>
 internal sealed class CircularBufferBuckets
 {
-    private long[] trait;
+    private long[]? trait;
     private int begin = 0;
     private int end = -1;
 
@@ -62,7 +64,12 @@ public CircularBufferBuckets(int capacity)
     /// </remarks>
     public long this[int index]
     {
-        get => this.trait[this.ModuloIndex(index)];
+        get
+        {
+            Debug.Assert(this.trait != null, "trait was null");
+
+            return this.trait![this.ModuloIndex(index)];
+        }
     }
 
     /// <summary>

src/OpenTelemetry/Metrics/CompositeMetricReader.cs

@@ -14,7 +14,10 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using OpenTelemetry.Internal;
 
 namespace OpenTelemetry.Metrics;
@@ -153,14 +156,15 @@ protected override void Dispose(bool disposing)
 
     public struct Enumerator
     {
-        private DoublyLinkedListNode node;
+        private DoublyLinkedListNode? node;
 
         internal Enumerator(DoublyLinkedListNode node)
         {
             this.node = node;
             this.Current = null;
         }
 
+        [AllowNull]
         public MetricReader Current { get; private set; }
 
         public bool MoveNext()
@@ -185,8 +189,8 @@ public DoublyLinkedListNode(MetricReader value)
             this.Value = value;
         }
 
-        public DoublyLinkedListNode Previous { get; set; }
+        public DoublyLinkedListNode? Previous { get; set; }
 
-        public DoublyLinkedListNode Next { get; set; }
+        public DoublyLinkedListNode? Next { get; set; }
     }
 }