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trace: Use non-generic to replace newEvictedQueue in trace.start to reduce memory usage. #5497

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Jun 17, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
- The exporter no longer exports the deprecated "otel.library.name" or "otel.library.version" attributes.
- Upgrade `go.opentelemetry.io/otel/semconv/v1.25.0` to `go.opentelemetry.io/otel/semconv/v1.26.0` in `go.opentelemetry.io/otel/sdk/resource`. (#5490)
- Upgrade `go.opentelemetry.io/otel/semconv/v1.25.0` to `go.opentelemetry.io/otel/semconv/v1.26.0` in `go.opentelemetry.io/otel/sdk/trace`. (#5490)
- `Tracer.Start` in `go.opentelemetry.io/otel/sdk/trace` use non-generic to replace `newEvictedQueue` to reduce memory allocation. (#5497)
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### Fixed

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17 changes: 11 additions & 6 deletions sdk/trace/evictedqueue.go
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@
package trace // import "go.opentelemetry.io/otel/sdk/trace"

import (
"fmt"
"slices"
"sync"

Expand All @@ -19,13 +18,19 @@ type evictedQueue[T any] struct {
logDropped func()
}

func newEvictedQueue[T any](capacity int) evictedQueue[T] {
var tVal T
msg := fmt.Sprintf("limit reached: dropping trace %T", tVal)
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func newEvictedQueueEvent(capacity int) evictedQueue[Event] {
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// Do not pre-allocate queue, do this lazily.
return evictedQueue[T]{
return evictedQueue[Event]{
capacity: capacity,
logDropped: sync.OnceFunc(func() { global.Warn(msg) }),
logDropped: sync.OnceFunc(func() { global.Warn("limit reached: dropping trace trace.Event") }),
}
}

func newEvictedQueueLink(capacity int) evictedQueue[Link] {
// Do not pre-allocate queue, do this lazily.
return evictedQueue[Link]{
capacity: capacity,
logDropped: sync.OnceFunc(func() { global.Warn("limit reached: dropping trace trace.Link") }),
}
}

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32 changes: 16 additions & 16 deletions sdk/trace/evictedqueue_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -14,47 +14,47 @@ func init() {
}

func TestAdd(t *testing.T) {
q := newEvictedQueue[string](3)
q.add("value1")
q.add("value2")
q := newEvictedQueueLink(3)
q.add(Link{})
q.add(Link{})
if wantLen, gotLen := 2, len(q.queue); wantLen != gotLen {
t.Errorf("got queue length %d want %d", gotLen, wantLen)
}
}

func TestCopy(t *testing.T) {
q := newEvictedQueue[string](3)
q.add("value1")
q := newEvictedQueueEvent(3)
q.add(Event{Name: "value1"})
cp := q.copy()

q.add("value2")
assert.Equal(t, []string{"value1"}, cp, "queue update modified copy")
q.add(Event{Name: "value2"})
assert.Equal(t, []Event{{Name: "value1"}}, cp, "queue update modified copy")

cp[0] = "value0"
assert.Equal(t, "value1", q.queue[0], "copy update modified queue")
cp[0] = Event{Name: "value0"}
assert.Equal(t, Event{Name: "value1"}, q.queue[0], "copy update modified queue")
}

func TestDropCount(t *testing.T) {
q := newEvictedQueue[string](3)
q := newEvictedQueueEvent(3)
var called bool
q.logDropped = func() { called = true }

q.add("value1")
q.add(Event{Name: "value1"})
assert.False(t, called, `"value1" logged as dropped`)
q.add("value2")
q.add(Event{Name: "value2"})
assert.False(t, called, `"value2" logged as dropped`)
q.add("value3")
q.add(Event{Name: "value3"})
assert.False(t, called, `"value3" logged as dropped`)
q.add("value1")
q.add(Event{Name: "value1"})
assert.True(t, called, `"value2" not logged as dropped`)
q.add("value4")
q.add(Event{Name: "value4"})
if wantLen, gotLen := 3, len(q.queue); wantLen != gotLen {
t.Errorf("got queue length %d want %d", gotLen, wantLen)
}
if wantDropCount, gotDropCount := 2, q.droppedCount; wantDropCount != gotDropCount {
t.Errorf("got drop count %d want %d", gotDropCount, wantDropCount)
}
wantArr := []string{"value3", "value1", "value4"}
wantArr := []Event{{Name: "value3"}, {Name: "value1"}, {Name: "value4"}}
gotArr := q.copy()

if wantLen, gotLen := len(wantArr), len(gotArr); gotLen != wantLen {
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13 changes: 13 additions & 0 deletions sdk/trace/trace_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -2107,3 +2107,16 @@ func TestAddLinkToNonRecordingSpan(t *testing.T) {
t.Errorf("AddLinkToNonRecordingSpan: -got +want %s", diff)
}
}

func BenchmarkTraceStart(b *testing.B) {
tracer := NewTracerProvider().Tracer("")
ctx := trace.ContextWithSpanContext(context.Background(), trace.SpanContext{})

b.ReportAllocs()
b.ResetTimer()

for i := 0; i < b.N; i++ {
_, span := tracer.Start(ctx, "")
span.End()
}
}
4 changes: 2 additions & 2 deletions sdk/trace/tracer.go
Original file line number Diff line number Diff line change
Expand Up @@ -132,8 +132,8 @@ func (tr *tracer) newRecordingSpan(psc, sc trace.SpanContext, name string, sr Sa
spanKind: trace.ValidateSpanKind(config.SpanKind()),
name: name,
startTime: startTime,
events: newEvictedQueue[Event](tr.provider.spanLimits.EventCountLimit),
links: newEvictedQueue[Link](tr.provider.spanLimits.LinkCountLimit),
events: newEvictedQueueEvent(tr.provider.spanLimits.EventCountLimit),
links: newEvictedQueueLink(tr.provider.spanLimits.LinkCountLimit),
tracer: tr,
}

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