Replace recordingSpan attributes implementation with map of attributes

CHANGELOG.md

@@ -17,6 +17,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Changed
 
 - Jaeger exporter takes into additional 70 bytes overhead into consideration when sending UDP packets (#2489, #2512)
+- The attributes returned from the `ReadOnlySpan` and `ReadWriteSpan` in `go.opentelemetry.io/otel/sdk/trace` are unordered.
+  Multiple calls to retrieve these attributes will return a slice of them that is not guaranteed to be in the same order.
+  If these attributes need to be consistently ordered, the `sort` package can be used.
+  Given these attributes will have unique keys `sort.Slice(attr, func(i, j int) bool { return attr[i].Key < attr[j].Key })` can be used to sort `attr` stably. (#2555)
 
 ### Deprecated
 
@@ -30,6 +34,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Change the `otlpmetric.Client` interface's `UploadMetrics` method to accept a single `ResourceMetrics` instead of a slice of them. (#2491)
 - Specify explicit buckets in Prometheus example. (#2493)
 - W3C baggage will now decode urlescaped values. (#2529)
+- The order attributes are dropped from spans in the `go.opentelemetry.io/otel/sdk/trace` package when capacity is reached is fixed to be in compliance with the OpenTelemetry specification.
+  Instead of dropping the least-recently-used attribute, the last added attribute is dropped.
+  This drop order still only applies to attributes with unique keys not already contained in the span.
+  If an attribute is added with a key already contained in the span, that attribute is updated to the new value being added. (#2555)
 
 ### Removed
 

exporters/otlp/otlptrace/otlptracegrpc/client_test.go

@@ -17,6 +17,7 @@ import (
 	"context"
 	"fmt"
 	"net"
+	"sort"
 	"strings"
 	"testing"
 	"time"
@@ -297,34 +298,34 @@ func TestNew_withMultipleAttributeTypes(t *testing.T) {
 
 	expected := []*commonpb.KeyValue{
 		{
-			Key: "Int",
+			Key: "Bool",
 			Value: &commonpb.AnyValue{
-				Value: &commonpb.AnyValue_IntValue{
-					IntValue: 1,
+				Value: &commonpb.AnyValue_BoolValue{
+					BoolValue: true,
 				},
 			},
 		},
 		{
-			Key: "Int64",
+			Key: "Float64",
 			Value: &commonpb.AnyValue{
-				Value: &commonpb.AnyValue_IntValue{
-					IntValue: 3,
+				Value: &commonpb.AnyValue_DoubleValue{
+					DoubleValue: 2.22,
 				},
 			},
 		},
 		{
-			Key: "Float64",
+			Key: "Int",
 			Value: &commonpb.AnyValue{
-				Value: &commonpb.AnyValue_DoubleValue{
-					DoubleValue: 2.22,
+				Value: &commonpb.AnyValue_IntValue{
+					IntValue: 1,
 				},
 			},
 		},
 		{
-			Key: "Bool",
+			Key: "Int64",
 			Value: &commonpb.AnyValue{
-				Value: &commonpb.AnyValue_BoolValue{
-					BoolValue: true,
+				Value: &commonpb.AnyValue_IntValue{
+					IntValue: 3,
 				},
 			},
 		},
@@ -339,10 +340,10 @@ func TestNew_withMultipleAttributeTypes(t *testing.T) {
 	}
 
 	// Verify attributes
-	if !assert.Len(t, rss[0].Attributes, len(expected)) {
-		t.Fatalf("attributes count: got %d, want %d\n", len(rss[0].Attributes), len(expected))
-	}
-	for i, actual := range rss[0].Attributes {
+	attr := rss[0].Attributes
+	require.Len(t, attr, len(expected))
+	sort.Slice(attr, func(i, j int) bool { return attr[i].Key < attr[j].Key })
+	for i, actual := range attr {
 		if a, ok := actual.Value.Value.(*commonpb.AnyValue_DoubleValue); ok {
 			e, ok := expected[i].Value.Value.(*commonpb.AnyValue_DoubleValue)
 			if !ok {

sdk/trace/benchmark_test.go

@@ -16,6 +16,7 @@ package trace_test
 
 import (
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
@@ -35,6 +36,28 @@ func BenchmarkStartEndSpan(b *testing.B) {
 	})
 }
 
+func BenchmarkSpanSetAttributesOverCapacity(b *testing.B) {
+	tp := sdktrace.NewTracerProvider(
+		sdktrace.WithSpanLimits(sdktrace.SpanLimits{AttributeCountLimit: 1}),
+	)
+	tracer := tp.Tracer("BenchmarkSpanSetAttributesOverCapacity")
+	ctx := context.Background()
+	attrs := make([]attribute.KeyValue, 128)
+	for i := range attrs {
+		key := fmt.Sprintf("key-%d", i)
+		attrs[i] = attribute.Bool(key, true)
+	}
+
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, span := tracer.Start(ctx, "/foo")
+		span.SetAttributes(attrs...)
+		span.End()
+	}
+}
+
 func BenchmarkSpanWithAttributes_4(b *testing.B) {
 	traceBenchmark(b, "Benchmark Start With 4 Attributes", func(b *testing.B, t trace.Tracer) {
 		ctx := context.Background()