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latencies.go
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latencies.go
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// MIT License
//
//
// Copyright 2023 Grabtaxi Holdings Pte Ltd (GRAB), All rights reserved.
//
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE
// Script taken from gandalf
package redis
import (
"sync/atomic"
)
type latencies struct {
values []int64
index int64
added int64
}
func newLatencies(l int) *latencies {
return &latencies{
values: make([]int64, l),
index: -1,
}
}
func (l *latencies) Add(value int64) {
index := atomic.AddInt64(&l.index, 1)
index = index % int64(len(l.values))
// the guarantee here is that the old value is replaced with a newer one
atomic.StoreInt64(&l.values[index], value)
// after the store, there are at least `added` number of elements
atomic.AddInt64(&l.added, 1)
}
func (l *latencies) Average() float64 {
var total int64
// we cannot use index since index is incremented before the swap occurs
added := int(atomic.LoadInt64(&l.added))
var length int
if added < len(l.values) {
length = added
} else {
length = len(l.values)
}
if length <= 0 {
return 0.0
}
// we are not concerned whether all values are atomically retrieved at once since we are sampling an estimate
for i := 0; i < length; i++ {
total += atomic.LoadInt64(&l.values[i])
}
return float64(total) / float64(length)
}