Allow GC to collect unneeded slice elements

Author: ash2k

CHANGELOG.md

@@ -41,6 +41,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Support scope attributes and make them as identifying for `Meter` in `go.opentelemetry.io/otel` and `go.opentelemetry.io/otel/sdk/metric`. (#5926)
 - Support scope attributes and make them as identifying for `Logger` in `go.opentelemetry.io/otel` and `go.opentelemetry.io/otel/sdk/log`. (#5925)
 - Make schema URL and scope attributes as identifying for `Tracer` in `go.opentelemetry.io/otel/bridge/opentracing`. (#5931)
+- Clear unneeded slice elements to allow GC to collect the objects in `go.opentelemetry.io/otel/sdk/log`, `go.opentelemetry.io/otel/metric`, and `go.opentelemetry.io/otel/trace`. (#5804)
 
 ### Removed
 

sdk/log/record.go

@@ -234,7 +234,7 @@ func (r *Record) AddAttributes(attrs ...log.KeyValue) {
 		//
 		// Do not use head(attrs, r.attributeCountLimit - n) here. If
 		// (r.attributeCountLimit - n) <= 0 attrs needs to be emptied.
-		last := max(0, (r.attributeCountLimit - n))
+		last := max(0, r.attributeCountLimit-n)
 		r.addDropped(len(attrs) - last)
 		attrs = attrs[:last]
 	}

sdk/metric/internal/aggregate/drop.go

@@ -22,5 +22,6 @@ func (r *dropRes[N]) Offer(context.Context, N, []attribute.KeyValue) {}
 
 // Collect resets dest. No exemplars will ever be returned.
 func (r *dropRes[N]) Collect(dest *[]exemplar.Exemplar) {
+	clear(*dest) // Erase elements to let GC collect objects
 	*dest = (*dest)[:0]
 }

sdk/metric/internal/aggregate/exemplar.go

@@ -17,6 +17,7 @@ var exemplarPool = sync.Pool{
 func collectExemplars[N int64 | float64](out *[]metricdata.Exemplar[N], f func(*[]exemplar.Exemplar)) {
 	dest := exemplarPool.Get().(*[]exemplar.Exemplar)
 	defer func() {
+		clear(*dest) // Erase elements to let GC collect objects
 		*dest = (*dest)[:0]
 		exemplarPool.Put(dest)
 	}()

sdk/metric/pipeline.go

@@ -115,6 +115,7 @@ func (p *pipeline) produce(ctx context.Context, rm *metricdata.ResourceMetrics)
 		}
 		if err := ctx.Err(); err != nil {
 			rm.Resource = nil
+			clear(rm.ScopeMetrics) // Erase elements to let GC collect objects
 			rm.ScopeMetrics = rm.ScopeMetrics[:0]
 			return err
 		}
@@ -128,6 +129,7 @@ func (p *pipeline) produce(ctx context.Context, rm *metricdata.ResourceMetrics)
 		if err := ctx.Err(); err != nil {
 			// This means the context expired before we finished running callbacks.
 			rm.Resource = nil
+			clear(rm.ScopeMetrics) // Erase elements to let GC collect objects
 			rm.ScopeMetrics = rm.ScopeMetrics[:0]
 			return err
 		}

sdk/trace/batch_span_processor.go

@@ -280,6 +280,7 @@ func (bsp *batchSpanProcessor) exportSpans(ctx context.Context) error {
 		//
 		// It is up to the exporter to implement any type of retry logic if a batch is failing
 		// to be exported, since it is specific to the protocol and backend being sent to.
+		clear(bsp.batch) // Erase elements to let GC collect objects
 		bsp.batch = bsp.batch[:0]
 
 		if err != nil {

sdk/trace/span.go

@@ -639,10 +639,7 @@ func (s *recordingSpan) dedupeAttrsFromRecord(record map[attribute.Key]int) {
 			record[a.Key] = len(unique) - 1
 		}
 	}
-	// s.attributes have element types of attribute.KeyValue. These types are
-	// not pointers and they themselves do not contain pointer fields,
-	// therefore the duplicate values do not need to be zeroed for them to be
-	// garbage collected.
+	clear(s.attributes[len(unique):]) // Erase unneeded elements to let GC collect objects
 	s.attributes = unique
 }