func (p *protocolV2) messagePump(client *nsqd.ClientV2, startedChan chan bool,
stoppedChan chan bool) {
var err error
var buf bytes.Buffer
var clientMsgChan chan *nsqd.Message
var subChannel *nsqd.Channel
// NOTE: `flusherChan` is used to bound message latency for
// the pathological case of a channel on a low volume topic
// with >1 clients having >1 RDY counts
var flusherChan <-chan time.Time
var sampleRate int32
subEventChan := client.SubEventChan
identifyEventChan := client.IdentifyEventChan
outputBufferTicker := time.NewTicker(client.OutputBufferTimeout)
heartbeatTicker := time.NewTicker(client.HeartbeatInterval)
heartbeatChan := heartbeatTicker.C
heartbeatFailedCnt := 0
msgTimeout := client.MsgTimeout
// v2 opportunistically buffers data to clients to reduce write system calls
// we force flush in two cases:
// 1. when the client is not ready to receive messages
// 2. we're buffered and the channel has nothing left to send us
// (ie. we would block in this loop anyway)
//
flushed := true
// signal to the goroutine that started the messagePump
// that we've started up
close(startedChan)
for {
if subChannel == nil || !client.IsReadyForMessages() {
// the client is not ready to receive messages...
clientMsgChan = nil
flusherChan = nil
// force flush
client.LockWrite()
err = client.Flush()
client.UnlockWrite()
if err != nil {
goto exit
}
flushed = true
} else if flushed {
// last iteration we flushed...
// do not select on the flusher ticker channel
clientMsgChan = subChannel.GetClientMsgChan()
flusherChan = nil
} else {
// we're buffered (if there isn't any more data we should flush)...
// select on the flusher ticker channel, too
clientMsgChan = subChannel.GetClientMsgChan()
flusherChan = outputBufferTicker.C
}
select {
case <-client.ExitChan:
goto exit
case <-flusherChan:
// if this case wins, we're either starved
// or we won the race between other channels...
// in either case, force flush
client.LockWrite()
err = client.Flush()
client.UnlockWrite()
if err != nil {
goto exit
}
flushed = true
case <-client.ReadyStateChan:
case subChannel = <-subEventChan:
// you can't SUB anymore
nsqd.NsqLogger().Logf("client %v sub to channel: %v", client.ID,
subChannel.GetName())
subEventChan = nil
case identifyData := <-identifyEventChan:
// you can't IDENTIFY anymore
identifyEventChan = nil
outputBufferTicker.Stop()
if identifyData.OutputBufferTimeout > 0 {
outputBufferTicker = time.NewTicker(identifyData.OutputBufferTimeout)
}
heartbeatTicker.Stop()
heartbeatChan = nil
if identifyData.HeartbeatInterval > 0 {
heartbeatTicker = time.NewTicker(identifyData.HeartbeatInterval)
heartbeatChan = heartbeatTicker.C
}
if identifyData.SampleRate > 0 {
sampleRate = identifyData.SampleRate
}
msgTimeout = identifyData.MsgTimeout
case <-heartbeatChan:
if subChannel != nil && client.IsReadyForMessages() {
// try wake up the channel
subChannel.TryWakeupRead()
}
err = Send(client, frameTypeResponse, heartbeatBytes)
nsqd.NsqLogger().LogDebugf("PROTOCOL(V2): [%s] send heartbeat", client)
if err != nil {
heartbeatFailedCnt++
nsqd.NsqLogger().LogWarningf("PROTOCOL(V2): [%s] send heartbeat failed %v times, %v", client, heartbeatFailedCnt, err)
if heartbeatFailedCnt > 2 {
goto exit
}
} else {
heartbeatFailedCnt = 0
}
case msg, ok := <-clientMsgChan:
if !ok {
goto exit
}
if sampleRate > 0 && rand.Int31n(100) > sampleRate {
// FIN automatically, all message will not wait to confirm if not sending,
// and the reader keep moving forward.
offset, _, _, _ := subChannel.ConfirmBackendQueue(msg)
// TODO: sync to replica nodes.
_ = offset
continue
}
// avoid re-send some confirmed message,
// this may happen while the channel reader is reset to old position
// due to some retry or leader change.
if subChannel.IsConfirmed(msg) {
continue
}
subChannel.StartInFlightTimeout(msg, client.ID, client.String(), msgTimeout)
client.SendingMessage()
err = SendMessage(client, msg, &buf, subChannel.IsOrdered())
if err != nil {
goto exit
}
flushed = false
}
}
exit:
nsqd.NsqLogger().LogDebugf("PROTOCOL(V2): [%s] exiting messagePump", client)
heartbeatTicker.Stop()
outputBufferTicker.Stop()
if err != nil {
nsqd.NsqLogger().Logf("PROTOCOL(V2): [%s] messagePump error - %s", client, err)
}
close(stoppedChan)
}