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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
// Copyright 2017, OpenCensus 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 zpages // import "go.opentelemetry.io/contrib/zpages"
import (
"time"
sdktrace "go.opentelemetry.io/otel/sdk/trace"
)
const (
// defaultBucketCapacity is the default capacity for every bucket (latency or error based).
defaultBucketCapacity = 10
// samplePeriod is the minimum time between accepting spans in a single bucket.
samplePeriod = time.Second
)
// bucket is a container for a set of spans for latency buckets or errored spans.
type bucket struct {
nextTime time.Time // next time we can accept a span
buffer []sdktrace.ReadOnlySpan // circular buffer of spans
nextIndex int // location next ReadOnlySpan should be placed in buffer
overflow bool // whether the circular buffer has wrapped around
}
// newBucket returns a new bucket with the given capacity.
func newBucket(capacity uint) *bucket {
return &bucket{
buffer: make([]sdktrace.ReadOnlySpan, capacity),
}
}
// add adds a span to the bucket, if nextTime has been reached.
func (b *bucket) add(s sdktrace.ReadOnlySpan) {
if s.EndTime().Before(b.nextTime) {
return
}
if len(b.buffer) == 0 {
return
}
b.nextTime = s.EndTime().Add(samplePeriod)
b.buffer[b.nextIndex] = s
b.nextIndex++
if b.nextIndex == len(b.buffer) {
b.nextIndex = 0
b.overflow = true
}
}
// len returns the number of spans in the bucket.
func (b *bucket) len() int {
if b.overflow {
return len(b.buffer)
}
return b.nextIndex
}
// spans returns the spans in this bucket.
func (b *bucket) spans() []sdktrace.ReadOnlySpan {
return append([]sdktrace.ReadOnlySpan(nil), b.buffer[0:b.len()]...)
}
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