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ackloop.go
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ackloop.go
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package memqueue
// ackLoop implements the brokers asynchronous ACK worker.
// Multiple concurrent ACKs from consecutive published batches will be batched up by the
// worker, to reduce the number of signals to return to the producer and the
// broker event loop.
// Producer ACKs are run in the ackLoop go-routine.
type ackLoop struct {
broker *Broker
sig chan batchAckMsg
lst chanList
totalACK uint64
totalSched uint64
batchesSched uint64
batchesACKed uint64
processACK func(chanList, int)
}
func newACKLoop(b *Broker, processACK func(chanList, int)) *ackLoop {
l := &ackLoop{broker: b}
l.processACK = processACK
return l
}
func (l *ackLoop) run() {
var (
// log = l.broker.logger
// Buffer up acked event counter in acked. If acked > 0, acks will be set to
// the broker.acks channel for sending the ACKs while potentially receiving
// new batches from the broker event loop.
// This concurrent bidirectionaly communication pattern requiring 'select'
// ensures we can not have any deadlock between the event loop and the ack
// loop, as the ack loop will not block on any channel
acked int
acks chan int
)
for {
select {
case <-l.broker.done:
// TODO: handle pending ACKs?
// TODO: panic on pending batches?
return
case acks <- acked:
acks, acked = nil, 0
case lst := <-l.broker.scheduledACKs:
count, events := lst.count()
l.lst.concat(&lst)
// log.Debug("ACK List:")
// for current := l.lst.head; current != nil; current = current.next {
// log.Debugf(" ack entry(seq=%v, start=%v, count=%v",
// current.seq, current.start, current.count)
// }
l.batchesSched += uint64(count)
l.totalSched += uint64(events)
case <-l.sig:
acked += l.handleBatchSig()
if acked > 0 {
acks = l.broker.acks
}
}
// log.Debug("ackloop INFO")
// log.Debug("ackloop: total events scheduled = ", l.totalSched)
// log.Debug("ackloop: total events ack = ", l.totalACK)
// log.Debug("ackloop: total batches scheduled = ", l.batchesSched)
// log.Debug("ackloop: total batches ack = ", l.batchesACKed)
l.sig = l.lst.channel()
// if l.sig == nil {
// log.Debug("ackloop: no ack scheduled")
// } else {
// log.Debug("ackloop: schedule ack: ", l.lst.head.seq)
// }
}
}
// handleBatchSig collects and handles a batch ACK/Cancel signal. handleBatchSig
// is run by the ackLoop.
func (l *ackLoop) handleBatchSig() int {
lst := l.collectAcked()
count := 0
for current := lst.front(); current != nil; current = current.next {
count += current.count
}
if count > 0 {
if e := l.broker.eventer; e != nil {
e.OnACK(count)
}
// report acks to waiting clients
l.processACK(lst, count)
}
for !lst.empty() {
releaseACKChan(lst.pop())
}
// return final ACK to EventLoop, in order to clean up internal buffer
l.broker.logger.Debug("ackloop: return ack to broker loop:", count)
l.totalACK += uint64(count)
l.broker.logger.Debug("ackloop: done send ack")
return count
}
func (l *ackLoop) collectAcked() chanList {
lst := chanList{}
acks := l.lst.pop()
l.onACK(acks)
lst.append(acks)
done := false
for !l.lst.empty() && !done {
acks := l.lst.front()
select {
case <-acks.ch:
l.onACK(acks)
lst.append(l.lst.pop())
default:
done = true
}
}
return lst
}
func (l *ackLoop) onACK(acks *ackChan) {
l.batchesACKed++
l.broker.logger.Debugf("ackloop: receive ack [%v: %v, %v]", acks.seq, acks.start, acks.count)
}