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listener.go
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/
listener.go
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// Copyright 2018 Istio 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 store
import (
"time"
"github.com/gogo/protobuf/proto"
"istio.io/istio/pkg/log"
)
// StartWatch registers with store, initiates a watch, and returns the current config state.
func StartWatch(s Store, kinds map[string]proto.Message) (map[Key]*Resource, <-chan Event, error) {
// create channel before listing.
watchChan, err := s.Watch()
if err != nil {
return nil, nil, err
}
return s.List(), watchChan, nil
}
// maxEvents is the likely maximum number of events
// we can expect in a second. It is used to avoid slice reallocation.
const maxEvents = 50
// ApplyEventsFn is used for testing
type ApplyEventsFn func(events []*Event)
// WatchChanges watches for changes on a channel and
// publishes a batch of changes via applyEvents.
// WatchChanges is started in a goroutine.
func WatchChanges(wch <-chan Event, stop <-chan struct{}, watchFlushDuration time.Duration, applyEvents ApplyEventsFn) {
// consume changes and apply them to data indefinitely
var timeChan <-chan time.Time
var timer *time.Timer
events := make([]*Event, 0, maxEvents)
for {
select {
case ev := <-wch:
if len(events) == 0 {
timer = time.NewTimer(watchFlushDuration)
timeChan = timer.C
}
events = append(events, &ev)
case <-timeChan:
timer.Stop()
timeChan = nil
log.Infof("Publishing %d events", len(events))
applyEvents(events)
events = events[:0]
case <-stop:
return
}
}
}