TUN-5989: Add in-memory otlp exporter

vendor/go.opentelemetry.io/otel/sdk/trace/evictedqueue.go

@@ -0,0 +1,44 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace // import "go.opentelemetry.io/otel/sdk/trace"
+
+// evictedQueue is a FIFO queue with a configurable capacity.
+type evictedQueue struct {
+	queue        []interface{}
+	capacity     int
+	droppedCount int
+}
+
+func newEvictedQueue(capacity int) evictedQueue {
+	// Do not pre-allocate queue, do this lazily.
+	return evictedQueue{capacity: capacity}
+}
+
+// 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) add(value interface{}) {
+	if eq.capacity == 0 {
+		eq.droppedCount++
+		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.queue = append(eq.queue, value)
+}