Convert Attribute to a struct (#581)

This avoids about 30% of allocations in benchmarks with 3 or more attributes and sampling enabled. ``` name old time/op new time/op delta StartEndSpan-8 522ns ± 0% 502ns ± 0% ~ (p=1.000 n=1+1) SpanWithAnnotations_3-8 1.22µs ± 0% 1.08µs ± 0% ~ (p=1.000 n=1+1) SpanWithAnnotations_6-8 1.66µs ± 0% 1.29µs ± 0% ~ (p=1.000 n=1+1) TraceID_DotString-8 191ns ± 0% 185ns ± 0% ~ (p=1.000 n=1+1) SpanID_DotString-8 172ns ± 0% 174ns ± 0% ~ (p=1.000 n=1+1) name old alloc/op new alloc/op delta StartEndSpan-8 576B ± 0% 576B ± 0% ~ (all equal) SpanWithAnnotations_3-8 1.37kB ± 0% 1.27kB ± 0% ~ (p=1.000 n=1+1) SpanWithAnnotations_6-8 1.49kB ± 0% 1.30kB ± 0% ~ (p=1.000 n=1+1) TraceID_DotString-8 80.0B ± 0% 80.0B ± 0% ~ (all equal) SpanID_DotString-8 56.0B ± 0% 56.0B ± 0% ~ (all equal) name old allocs/op new allocs/op delta StartEndSpan-8 4.00 ± 0% 4.00 ± 0% ~ (all equal) SpanWithAnnotations_3-8 13.0 ± 0% 10.0 ± 0% ~ (p=1.000 n=1+1) SpanWithAnnotations_6-8 18.0 ± 0% 12.0 ± 0% ~ (p=1.000 n=1+1) TraceID_DotString-8 3.00 ± 0% 3.00 ± 0% ~ (all equal) SpanID_DotString-8 3.00 ± 0% 3.00 ± 0% ~ (all equal) ```
census-instrumentation · Mar 14, 2018 · 821173a · 821173a
1 parent 3539f4d
commit 821173a
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Showing 3 changed files with 75 additions and 82 deletions.
diff --git a/trace/basetypes.go b/trace/basetypes.go
@@ -41,46 +41,26 @@ type Annotation struct {
 	Attributes map[string]interface{}
 }
 
-// Attribute is an interface for attributes;
-// it is implemented by BoolAttribute, IntAttribute, and StringAttribute.
-type Attribute interface {
-	isAttribute()
+// Attribute represents a key-value pair on a span, link or annotation.
+// Construct with one of: BoolAttribute, Int64Attribute, or StringAttribute.
+type Attribute struct {
+	key   string
+	value interface{}
 }
 
 // BoolAttribute returns a bool-valued attribute.
 func BoolAttribute(key string, value bool) Attribute {
-	return boolAttribute{key: key, value: value}
-}
-
-type boolAttribute struct {
-	key   string
-	value bool
+	return Attribute{key: key, value: value}
 }
 
-func (b boolAttribute) isAttribute() {}
-
-type int64Attribute struct {
-	key   string
-	value int64
-}
-
-func (i int64Attribute) isAttribute() {}
-
 // Int64Attribute returns an int64-valued attribute.
 func Int64Attribute(key string, value int64) Attribute {
-	return int64Attribute{key: key, value: value}
-}
-
-type stringAttribute struct {
-	key   string
-	value string
+	return Attribute{key: key, value: value}
 }
 
-func (s stringAttribute) isAttribute() {}
-
 // StringAttribute returns a string-valued attribute.
 func StringAttribute(key string, value string) Attribute {
-	return stringAttribute{key: key, value: value}
+	return Attribute{key: key, value: value}
 }
 
 // LinkType specifies the relationship between the span that had the link

diff --git a/trace/benchmark_test.go b/trace/benchmark_test.go
@@ -20,66 +20,86 @@ import (
 )
 
 func BenchmarkStartEndSpan(b *testing.B) {
-	ctx := context.Background()
-	b.ResetTimer()
-
-	for i := 0; i < b.N; i++ {
-		_, span := StartSpan(ctx, "/foo")
-		span.End()
-	}
+	traceBenchmark(b, func(b *testing.B) {
+		ctx := context.Background()
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			_, span := StartSpan(ctx, "/foo")
+			span.End()
+		}
+	})
 }
 
 func BenchmarkSpanWithAnnotations_3(b *testing.B) {
-	ctx := context.Background()
-	b.ResetTimer()
+	traceBenchmark(b, func(b *testing.B) {
+		ctx := context.Background()
+		b.ResetTimer()
 
-	for i := 0; i < b.N; i++ {
-		_, span := StartSpan(ctx, "/foo")
-		span.SetAttributes(
-			BoolAttribute("key1", false),
-			StringAttribute("key2", "hello"),
-			Int64Attribute("key3", 123),
-		)
-		span.End()
-	}
+		for i := 0; i < b.N; i++ {
+			_, span := StartSpan(ctx, "/foo")
+			span.SetAttributes(
+				BoolAttribute("key1", false),
+				StringAttribute("key2", "hello"),
+				Int64Attribute("key3", 123),
+			)
+			span.End()
+		}
+	})
 }
 
 func BenchmarkSpanWithAnnotations_6(b *testing.B) {
-	ctx := context.Background()
-	b.ResetTimer()
+	traceBenchmark(b, func(b *testing.B) {
+		ctx := context.Background()
+		b.ResetTimer()
 
-	for i := 0; i < b.N; i++ {
-		_, span := StartSpan(ctx, "/foo")
-		span.SetAttributes(
-			BoolAttribute("key1", false),
-			BoolAttribute("key2", true),
-			StringAttribute("key3", "hello"),
-			StringAttribute("key4", "hello"),
-			Int64Attribute("key5", 123),
-			Int64Attribute("key6", 456),
-		)
-		span.End()
-	}
+		for i := 0; i < b.N; i++ {
+			_, span := StartSpan(ctx, "/foo")
+			span.SetAttributes(
+				BoolAttribute("key1", false),
+				BoolAttribute("key2", true),
+				StringAttribute("key3", "hello"),
+				StringAttribute("key4", "hello"),
+				Int64Attribute("key5", 123),
+				Int64Attribute("key6", 456),
+			)
+			span.End()
+		}
+	})
 }
 
 func BenchmarkTraceID_DotString(b *testing.B) {
-	b.ReportAllocs()
-	t := TraceID{0x0D, 0x0E, 0x0A, 0x0D, 0x0B, 0x0E, 0x0E, 0x0F, 0x0F, 0x0E, 0x0E, 0x0B, 0x0D, 0x0A, 0x0E, 0x0D}
-	want := "0d0e0a0d0b0e0e0f0f0e0e0b0d0a0e0d"
-	for i := 0; i < b.N; i++ {
-		if got := t.String(); got != want {
-			b.Fatalf("got = %q want = %q", got, want)
+	traceBenchmark(b, func(b *testing.B) {
+		t := TraceID{0x0D, 0x0E, 0x0A, 0x0D, 0x0B, 0x0E, 0x0E, 0x0F, 0x0F, 0x0E, 0x0E, 0x0B, 0x0D, 0x0A, 0x0E, 0x0D}
+		want := "0d0e0a0d0b0e0e0f0f0e0e0b0d0a0e0d"
+		for i := 0; i < b.N; i++ {
+			if got := t.String(); got != want {
+				b.Fatalf("got = %q want = %q", got, want)
+			}
 		}
-	}
+	})
 }
 
 func BenchmarkSpanID_DotString(b *testing.B) {
-	b.ReportAllocs()
-	s := SpanID{0x0D, 0x0E, 0x0A, 0x0D, 0x0B, 0x0E, 0x0E, 0x0F}
-	want := "0d0e0a0d0b0e0e0f"
-	for i := 0; i < b.N; i++ {
-		if got := s.String(); got != want {
-			b.Fatalf("got = %q want = %q", got, want)
+	traceBenchmark(b, func(b *testing.B) {
+		s := SpanID{0x0D, 0x0E, 0x0A, 0x0D, 0x0B, 0x0E, 0x0E, 0x0F}
+		want := "0d0e0a0d0b0e0e0f"
+		for i := 0; i < b.N; i++ {
+			if got := s.String(); got != want {
+				b.Fatalf("got = %q want = %q", got, want)
+			}
 		}
-	}
+	})
+}
+
+func traceBenchmark(b *testing.B, fn func(*testing.B)) {
+	b.Run("AlwaysSample", func(b *testing.B) {
+		b.ReportAllocs()
+		SetDefaultSampler(AlwaysSample())
+		fn(b)
+	})
+	b.Run("NeverSample", func(b *testing.B) {
+		b.ReportAllocs()
+		SetDefaultSampler(NeverSample())
+		fn(b)
+	})
 }
diff --git a/trace/trace.go b/trace/trace.go
@@ -273,14 +273,7 @@ func (s *Span) SetAttributes(attributes ...Attribute) {
 // copyAttributes copies a slice of Attributes into a map.
 func copyAttributes(m map[string]interface{}, attributes []Attribute) {
 	for _, a := range attributes {
-		switch a := a.(type) {
-		case boolAttribute:
-			m[a.key] = a.value
-		case int64Attribute:
-			m[a.key] = a.value
-		case stringAttribute:
-			m[a.key] = a.value
-		}
+		m[a.key] = a.value
 	}
 }