func (k *kvChannelIndex) pollForChanges(stableClock base.SequenceClock, newChannelClock base.SequenceClock) (hasChanges bool, cancelPolling bool) {
changeCacheExpvars.Add(fmt.Sprintf("pollCount-%s", k.channelName), 1)
// Increment the overall poll count since a changes request (regardless of whether there have been polled changes)
totalPollCount := atomic.AddUint32(&k.pollCount, 1)
unreadPollCount := atomic.LoadUint32(&k.unreadPollCount)
if unreadPollCount > kMaxUnreadPollCount {
// We've sent a notify, but had (kMaxUnreadPollCount) polls without anyone calling getChanges.
// Assume nobody is listening for updates - cancel polling for this channel
return false, true
}
if unreadPollCount > 0 {
// Give listeners more time to call getChanges, but increment
atomic.AddUint32(&k.unreadPollCount, 1)
}
k.lastPolledLock.Lock()
defer k.lastPolledLock.Unlock()
// First poll handling
if k.lastPolledChannelClock == nil {
k.lastPolledChannelClock = k.clock.Copy()
k.lastPolledSince = k.clock.Copy()
k.lastPolledValidTo = k.clock.Copy()
}
if !newChannelClock.AnyAfter(k.lastPolledChannelClock) {
// No changes to channel clock - update validTo based on the new stable sequence
k.lastPolledValidTo.SetTo(stableClock)
// If we've exceeded empty poll count, return hasChanges=true to trigger the "is
// anyone listening" check
if totalPollCount > kMaxEmptyPollCount {
return true, false
} else {
return false, false
}
}
// The clock has changed - load the changes and store in last polled
if err := k.updateLastPolled(stableClock, newChannelClock); err != nil {
base.Warn("Error updating last polled for channel %s: %v", k.channelName, err)
return false, false
}
// We have changes - increment unread counter if we haven't already
if unreadPollCount == 0 {
atomic.AddUint32(&k.unreadPollCount, 1)
}
return true, false
}
