/
internal_poller_autoscaler.go
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/
internal_poller_autoscaler.go
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// Copyright (c) 2017-2021 Uber Technologies Inc.
//
// 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.
package internal
import (
"context"
"errors"
"sync"
"time"
"github.com/marusama/semaphore/v2"
"go.uber.org/atomic"
"go.uber.org/zap"
"go.uber.org/cadence/internal/common/autoscaler"
)
// defaultPollerScalerCooldownInSeconds
const (
defaultPollerAutoScalerCooldown = time.Minute
defaultPollerAutoScalerTargetUtilization = 0.6
defaultMinConcurrentPollerSize = 1
)
var (
_ autoscaler.AutoScaler = (*pollerAutoScaler)(nil)
_ autoscaler.Estimator = (*pollerUsageEstimator)(nil)
)
type (
pollerAutoScaler struct {
pollerUsageEstimator
isDryRun bool
cooldownTime time.Duration
logger *zap.Logger
sem semaphore.Semaphore // resizable semaphore to control number of concurrent pollers
ctx context.Context
cancel context.CancelFunc
wg *sync.WaitGroup // graceful stop
recommender autoscaler.Recommender
onAutoScale []func() // hook functions that run post autoscale
}
pollerUsageEstimator struct {
// This single atomic variable stores two variables:
// left 32 bits is noTaskCounts, right 32 bits is taskCounts.
// This avoids unnecessary usage of CompareAndSwap
atomicBits *atomic.Uint64
}
pollerAutoScalerOptions struct {
Enabled bool
InitCount int
MinCount int
MaxCount int
Cooldown time.Duration
DryRun bool
TargetUtilization float64
}
)
func newPollerScaler(
options pollerAutoScalerOptions,
logger *zap.Logger,
hooks ...func()) *pollerAutoScaler {
ctx, cancel := context.WithCancel(context.Background())
if !options.Enabled {
return nil
}
return &pollerAutoScaler{
isDryRun: options.DryRun,
cooldownTime: options.Cooldown,
logger: logger,
sem: semaphore.New(options.InitCount),
wg: &sync.WaitGroup{},
ctx: ctx,
cancel: cancel,
pollerUsageEstimator: pollerUsageEstimator{atomicBits: atomic.NewUint64(0)},
recommender: autoscaler.NewLinearRecommender(
autoscaler.ResourceUnit(options.MinCount),
autoscaler.ResourceUnit(options.MaxCount),
autoscaler.Usages{
autoscaler.PollerUtilizationRate: autoscaler.MilliUsage(options.TargetUtilization * 1000),
},
),
onAutoScale: hooks,
}
}
// Acquire concurrent poll quota
func (p *pollerAutoScaler) Acquire(resource autoscaler.ResourceUnit) error {
return p.sem.Acquire(p.ctx, int(resource))
}
// Release concurrent poll quota
func (p *pollerAutoScaler) Release(resource autoscaler.ResourceUnit) {
p.sem.Release(int(resource))
}
// GetCurrent poll quota
func (p *pollerAutoScaler) GetCurrent() autoscaler.ResourceUnit {
return autoscaler.ResourceUnit(p.sem.GetLimit())
}
// Start an auto-scaler go routine and returns a done to stop it
func (p *pollerAutoScaler) Start() {
logger := p.logger.Sugar()
p.wg.Add(1)
go func() {
defer p.wg.Done()
for {
select {
case <-p.ctx.Done():
return
case <-time.After(p.cooldownTime):
currentResource := autoscaler.ResourceUnit(p.sem.GetLimit())
currentUsages, err := p.pollerUsageEstimator.Estimate()
if err != nil {
logger.Warnw("poller autoscaler skip due to estimator error", "error", err)
continue
}
proposedResource := p.recommender.Recommend(currentResource, currentUsages)
logger.Debugw("poller autoscaler recommendation",
"currentUsage", currentUsages,
"current", uint64(currentResource),
"recommend", uint64(proposedResource),
"isDryRun", p.isDryRun)
if !p.isDryRun {
p.sem.SetLimit(int(proposedResource))
}
p.pollerUsageEstimator.Reset()
// hooks
for i := range p.onAutoScale {
p.onAutoScale[i]()
}
}
}
}()
return
}
// Stop stops the poller autoscaler
func (p *pollerAutoScaler) Stop() {
p.cancel()
p.wg.Wait()
}
// Reset metrics from the start
func (m *pollerUsageEstimator) Reset() {
m.atomicBits.Store(0)
}
// CollectUsage counts past poll results to estimate autoscaler.Usages
func (m *pollerUsageEstimator) CollectUsage(data interface{}) error {
isEmpty, err := isTaskEmpty(data)
if err != nil {
return err
}
if isEmpty { // no-task poll
m.atomicBits.Add(1 << 32)
} else {
m.atomicBits.Add(1)
}
return nil
}
func isTaskEmpty(task interface{}) (bool, error) {
switch t := task.(type) {
case *workflowTask:
return t == nil || t.task == nil, nil
case *activityTask:
return t == nil || t.task == nil, nil
case *localActivityTask:
return t == nil || t.workflowTask == nil, nil
default:
return false, errors.New("unknown task type")
}
}
// Estimate is based on past poll counts
func (m *pollerUsageEstimator) Estimate() (autoscaler.Usages, error) {
bits := m.atomicBits.Load()
noTaskCounts := bits >> 32 // left 32 bits
taskCounts := bits & ((1 << 32) - 1) // right 32 bits
if noTaskCounts+taskCounts == 0 {
return nil, errors.New("autoscaler.Estimator::Estimate error: not enough data")
}
return autoscaler.Usages{
autoscaler.PollerUtilizationRate: autoscaler.MilliUsage(taskCounts * 1000 / (noTaskCounts + taskCounts)),
}, nil
}