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coalesce.go
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coalesce.go
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package serf
import (
"time"
)
// coalescer is a simple interface that must be implemented to be
// used inside of a coalesceLoop
type coalescer interface {
// Can the coalescer handle this event, if not it is
// directly passed through to the destination channel
Handle(Event) bool
// Invoked to coalesce the given event
Coalesce(Event)
// Invoked to flush the coalesced events
Flush(outChan chan<- Event)
}
// coalescedEventCh returns an event channel where the events are coalesced
// using the given coalescer.
func coalescedEventCh(outCh chan<- Event, shutdownCh <-chan struct{},
cPeriod time.Duration, qPeriod time.Duration, c coalescer) chan<- Event {
inCh := make(chan Event, 1024)
go coalesceLoop(inCh, outCh, shutdownCh, cPeriod, qPeriod, c)
return inCh
}
// coalesceLoop is a simple long-running routine that manages the high-level
// flow of coalescing based on quiescence and a maximum quantum period.
func coalesceLoop(inCh <-chan Event, outCh chan<- Event, shutdownCh <-chan struct{},
coalescePeriod time.Duration, quiescentPeriod time.Duration, c coalescer) {
var quiescent <-chan time.Time
var quantum <-chan time.Time
shutdown := false
INGEST:
// Reset the timers
quantum = nil
quiescent = nil
for {
select {
case e := <-inCh:
// Ignore any non handled events
if !c.Handle(e) {
outCh <- e
continue
}
// Start a new quantum if we need to
// and restart the quiescent timer
if quantum == nil {
quantum = time.After(coalescePeriod)
}
quiescent = time.After(quiescentPeriod)
// Coalesce the event
c.Coalesce(e)
case <-quantum:
goto FLUSH
case <-quiescent:
goto FLUSH
case <-shutdownCh:
shutdown = true
goto FLUSH
}
}
FLUSH:
// Flush the coalesced events
c.Flush(outCh)
// Restart ingestion if we are not done
if !shutdown {
goto INGEST
}
}