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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package trace // import "go.opentelemetry.io/otel/sdk/trace"
import (
"slices"
"sync"
"go.opentelemetry.io/otel/internal/global"
)
// evictedQueue is a FIFO queue with a configurable capacity.
type evictedQueue[T any] struct {
queue []T
capacity int
droppedCount int
logDropped func()
}
func newEvictedQueueEvent(capacity int) evictedQueue[Event] {
// Do not pre-allocate queue, do this lazily.
return evictedQueue[Event]{
capacity: capacity,
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") }),
}
}
// add adds value to the evictedQueue eq. If eq is at capacity, the oldest
// queued value will be discarded and the drop count incremented.
func (eq *evictedQueue[T]) add(value T) {
if eq.capacity == 0 {
eq.droppedCount++
eq.logDropped()
return
}
if eq.capacity > 0 && len(eq.queue) == eq.capacity {
// Drop first-in while avoiding allocating more capacity to eq.queue.
copy(eq.queue[:eq.capacity-1], eq.queue[1:])
eq.queue = eq.queue[:eq.capacity-1]
eq.droppedCount++
eq.logDropped()
}
eq.queue = append(eq.queue, value)
}
// copy returns a copy of the evictedQueue.
func (eq *evictedQueue[T]) copy() []T {
return slices.Clone(eq.queue)
}
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