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/
stats.go
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/
stats.go
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/*
Copyright 2018 The Knative 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 queue
import (
"time"
"knative.dev/serving/pkg/autoscaler"
)
// ReqEvent represents either an incoming or closed request.
type ReqEvent struct {
Time time.Time
EventType ReqEventType
}
// ReqEventType denotes the type (incoming/closed) of a ReqEvent.
type ReqEventType int
const (
// ReqIn represents an incoming request
ReqIn ReqEventType = iota
// ReqOut represents a finished request
ReqOut
// ProxiedIn represents an incoming request through a proxy.
ProxiedIn
// ProxiedOut represents a finished proxied request.
ProxiedOut
)
// Channels is a structure for holding the channels for driving Stats.
// It's just to make the NewStats signature easier to read.
type Channels struct {
// Ticks with every request arrived/completed respectively
ReqChan chan ReqEvent
// Ticks with every stat report request
ReportChan <-chan time.Time
// Stat reporting channel
StatChan chan autoscaler.Stat
}
// Stats is a structure for holding channels per pod.
type Stats struct {
podName string
ch Channels
}
// NewStats instantiates a new instance of Stats.
func NewStats(podName string, channels Channels, startedAt time.Time) *Stats {
s := &Stats{
podName: podName,
ch: channels,
}
go func() {
var (
requestCount float64
proxiedCount float64
concurrency int32
proxiedConcurrency int32
)
lastChange := startedAt
timeOnConcurrency := make(map[int32]time.Duration)
timeOnProxiedConcurrency := make(map[int32]time.Duration)
// Updates the lastChanged/timeOnConcurrency state
// Note: Due to nature of the channels used below, the ReportChan
// can race the ReqChan, thus an event can arrive that has a lower
// timestamp than `lastChange`. This is ignored, since it only makes
// for very slight differences.
updateState := func(time time.Time) {
if time.After(lastChange) {
durationSinceChange := time.Sub(lastChange)
timeOnConcurrency[concurrency] += durationSinceChange
timeOnProxiedConcurrency[proxiedConcurrency] += durationSinceChange
lastChange = time
}
}
for {
select {
case event := <-s.ch.ReqChan:
updateState(event.Time)
switch event.EventType {
case ProxiedIn:
proxiedConcurrency++
proxiedCount++
fallthrough
case ReqIn:
requestCount++
concurrency++
case ProxiedOut:
proxiedConcurrency--
fallthrough
case ReqOut:
concurrency--
}
case now := <-s.ch.ReportChan:
updateState(now)
stat := autoscaler.Stat{
Time: now,
PodName: s.podName,
AverageConcurrentRequests: weightedAverage(timeOnConcurrency),
AverageProxiedConcurrentRequests: weightedAverage(timeOnProxiedConcurrency),
RequestCount: requestCount,
ProxiedRequestCount: proxiedCount,
}
// Send the stat to another goroutine to transmit
// so we can continue bucketing stats.
s.ch.StatChan <- stat
// Reset the stat counts which have been reported.
timeOnConcurrency = make(map[int32]time.Duration)
timeOnProxiedConcurrency = make(map[int32]time.Duration)
requestCount = 0
proxiedCount = 0
}
}
}()
return s
}
func weightedAverage(times map[int32]time.Duration) float64 {
var totalTimeUsed time.Duration
for _, val := range times {
totalTimeUsed += val
}
avg := 0.0
if totalTimeUsed > 0 {
sum := 0.0
for c, val := range times {
sum += float64(c) * val.Seconds()
}
avg = sum / totalTimeUsed.Seconds()
}
return avg
}