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// Copyright 2015 The etcd 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 v2stats
import (
"sync"
"time"
)
const (
queueCapacity = 200
)
// RequestStats represent the stats for a request.
// It encapsulates the sending time and the size of the request.
type RequestStats struct {
SendingTime time.Time
Size int
}
type statsQueue struct {
items [queueCapacity]*RequestStats
size int
front int
back int
totalReqSize int
rwl sync.RWMutex
}
func (q *statsQueue) Len() int {
return q.size
}
func (q *statsQueue) ReqSize() int {
return q.totalReqSize
}
// FrontAndBack gets the front and back elements in the queue
// We must grab front and back together with the protection of the lock
func (q *statsQueue) frontAndBack() (*RequestStats, *RequestStats) {
q.rwl.RLock()
defer q.rwl.RUnlock()
if q.size != 0 {
return q.items[q.front], q.items[q.back]
}
return nil, nil
}
// Insert function insert a RequestStats into the queue and update the records
func (q *statsQueue) Insert(p *RequestStats) {
q.rwl.Lock()
defer q.rwl.Unlock()
q.back = (q.back + 1) % queueCapacity
if q.size == queueCapacity { //dequeue
q.totalReqSize -= q.items[q.front].Size
q.front = (q.back + 1) % queueCapacity
} else {
q.size++
}
q.items[q.back] = p
q.totalReqSize += q.items[q.back].Size
}
// Rate function returns the package rate and byte rate
func (q *statsQueue) Rate() (float64, float64) {
front, back := q.frontAndBack()
if front == nil || back == nil {
return 0, 0
}
if time.Since(back.SendingTime) > time.Second {
q.Clear()
return 0, 0
}
sampleDuration := back.SendingTime.Sub(front.SendingTime)
pr := float64(q.Len()) / float64(sampleDuration) * float64(time.Second)
br := float64(q.ReqSize()) / float64(sampleDuration) * float64(time.Second)
return pr, br
}
// Clear function clear up the statsQueue
func (q *statsQueue) Clear() {
q.rwl.Lock()
defer q.rwl.Unlock()
q.back = -1
q.front = 0
q.size = 0
q.totalReqSize = 0
}
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