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holdoff.go
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holdoff.go
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// Copyright © 2018 Heptio
// 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 contour contains the translation business logic that listens
// to Kubernetes ResourceEventHandler events and translates those into
// additions/deletions in caches connected to the Envoy xDS gRPC API server.
package contour
import (
"sync"
"time"
"github.com/heptio/contour/internal/dag"
"github.com/heptio/contour/internal/metrics"
"github.com/sirupsen/logrus"
)
const (
holdoffDelay = 100 * time.Millisecond
holdoffMaxDelay = 500 * time.Millisecond
)
// A HoldoffNotifier delays calls to OnChange in the hope of
// coalescing rapid calls into a single update.
type HoldoffNotifier struct {
// Notifier to be called after delay.
Notifier
*metrics.Metrics
logrus.FieldLogger
mu sync.Mutex
timer *time.Timer
last time.Time
}
func (hn *HoldoffNotifier) OnChange(builder *dag.Builder) {
hn.mu.Lock()
defer hn.mu.Unlock()
if hn.timer != nil {
hn.timer.Stop()
}
since := time.Since(hn.last)
if since > holdoffMaxDelay {
// update immediately
hn.WithField("last update", since).Info("forcing update")
hn.Notifier.OnChange(builder)
hn.last = time.Now()
hn.Metrics.SetDAGRebuiltMetric(hn.last.Unix())
return
}
hn.WithField("remaining", holdoffMaxDelay-since).Info("delaying update")
hn.timer = time.AfterFunc(holdoffDelay, func() {
hn.mu.Lock()
defer hn.mu.Unlock()
hn.WithField("last update", time.Since(hn.last)).Info("performing delayed update")
hn.Notifier.OnChange(builder)
hn.last = time.Now()
hn.Metrics.SetDAGRebuiltMetric(hn.last.Unix())
})
}