Clean up aggregator via helper methods

Also get rid of forceFlushThreshold it does not need its own function

async_producer.go

@@ -9,10 +9,6 @@ import (
 	"github.com/eapache/queue"
 )
 
-func forceFlushThreshold() int {
-	return int(MaxRequestSize - (10 * 1024)) // 10KiB is safety room for misc. overhead, we might want to calculate this more precisely?
-}
-
 // AsyncProducer publishes Kafka messages using a non-blocking API. It routes messages
 // to the correct broker for the provided topic-partition, refreshing metadata as appropriate,
 // and parses responses for errors. You must read from the Errors() channel or the
@@ -491,6 +487,7 @@ func (pp *partitionProducer) updateLeader() error {
 	})
 }
 
+// one per broker, constructs both an aggregator and a flusher
 func (p *asyncProducer) newBrokerProducer(broker *Broker) chan<- *ProducerMessage {
 	input := make(chan *ProducerMessage)
 	bridge := make(chan []*ProducerMessage)
@@ -514,28 +511,21 @@ func (p *asyncProducer) newBrokerProducer(broker *Broker) chan<- *ProducerMessag
 	return input
 }
 
-// one per broker
 // groups messages together into appropriately-sized batches for sending to the broker
 // based on https://godoc.org/github.com/eapache/channels#BatchingChannel
 type aggregator struct {
 	parent *asyncProducer
 	broker *Broker
 	input  <-chan *ProducerMessage
 	output chan<- []*ProducerMessage
+
+	buffer      []*ProducerMessage
+	bufferBytes int
+	timer       <-chan time.Time
 }
 
 func (a *aggregator) run() {
-	var (
-		timer            <-chan time.Time
-		buffer           []*ProducerMessage
-		flushTriggered   chan<- []*ProducerMessage
-		bytesAccumulated int
-		defaultFlush     bool
-	)
-
-	if a.parent.conf.Producer.Flush.Frequency == 0 && a.parent.conf.Producer.Flush.Bytes == 0 && a.parent.conf.Producer.Flush.Messages == 0 {
-		defaultFlush = true
-	}
+	var output chan<- []*ProducerMessage
 
 	for {
 		select {
@@ -544,45 +534,77 @@ func (a *aggregator) run() {
 				goto shutdown
 			}
 
-			if (bytesAccumulated+msg.byteSize() >= forceFlushThreshold()) ||
-				(a.parent.conf.Producer.Compression != CompressionNone && bytesAccumulated+msg.byteSize() >= a.parent.conf.Producer.MaxMessageBytes) ||
-				(a.parent.conf.Producer.Flush.MaxMessages > 0 && len(buffer) >= a.parent.conf.Producer.Flush.MaxMessages) {
+			if a.wouldOverflow(msg) {
 				Logger.Printf("producer/aggregator/%d maximum request accumulated, forcing blocking flush\n", a.broker.ID())
-				a.output <- buffer
-				timer = nil
-				buffer = nil
-				flushTriggered = nil
-				bytesAccumulated = 0
+				a.output <- a.buffer
+				a.reset()
+				output = nil
 			}
 
-			buffer = append(buffer, msg)
-			bytesAccumulated += msg.byteSize()
+			a.buffer = append(a.buffer, msg)
+			a.bufferBytes += msg.byteSize()
 
-			if defaultFlush ||
-				msg.flags&chaser == chaser ||
-				(a.parent.conf.Producer.Flush.Messages > 0 && len(buffer) >= a.parent.conf.Producer.Flush.Messages) ||
-				(a.parent.conf.Producer.Flush.Bytes > 0 && bytesAccumulated >= a.parent.conf.Producer.Flush.Bytes) {
-				flushTriggered = a.output
-			} else if a.parent.conf.Producer.Flush.Frequency > 0 && timer == nil {
-				timer = time.After(a.parent.conf.Producer.Flush.Frequency)
+			if a.readyToFlush(msg) {
+				output = a.output
+			} else if a.parent.conf.Producer.Flush.Frequency > 0 && a.timer == nil {
+				a.timer = time.After(a.parent.conf.Producer.Flush.Frequency)
 			}
-		case <-timer:
-			flushTriggered = a.output
-		case flushTriggered <- buffer:
-			timer = nil
-			buffer = nil
-			flushTriggered = nil
-			bytesAccumulated = 0
+		case <-a.timer:
+			output = a.output
+		case output <- a.buffer:
+			a.reset()
+			output = nil
 		}
 	}
 
 shutdown:
-	if len(buffer) > 0 {
-		a.output <- buffer
+	if len(a.buffer) > 0 {
+		a.output <- a.buffer
 	}
 	close(a.output)
 }
 
+func (a *aggregator) wouldOverflow(msg *ProducerMessage) bool {
+	switch {
+	// Would we overflow our maximum possible size-on-the-wire? 10KiB is arbitrary overhead for safety.
+	case a.bufferBytes+msg.byteSize() >= int(MaxRequestSize-(10*1024)):
+		return true
+	// Would we overflow the size-limit of a compressed message-batch?
+	case a.parent.conf.Producer.Compression != CompressionNone && a.bufferBytes+msg.byteSize() >= a.parent.conf.Producer.MaxMessageBytes:
+		return true
+	// Would we overflow simply in number of messages?
+	case a.parent.conf.Producer.Flush.MaxMessages > 0 && len(a.buffer) >= a.parent.conf.Producer.Flush.MaxMessages:
+		return true
+	default:
+		return false
+	}
+}
+
+func (a *aggregator) readyToFlush(msg *ProducerMessage) bool {
+	switch {
+	// If all three config values are 0, we always flush as-fast-as-possible
+	case a.parent.conf.Producer.Flush.Frequency == 0 && a.parent.conf.Producer.Flush.Bytes == 0 && a.parent.conf.Producer.Flush.Messages == 0:
+		return true
+	// If the messages is a chaser we must flush to maintain the state-machine
+	case msg.flags&chaser == chaser:
+		return true
+	// If we've  passed the message trigger-point
+	case a.parent.conf.Producer.Flush.Messages > 0 && len(a.buffer) >= a.parent.conf.Producer.Flush.Messages:
+		return true
+	// If we've  passed the byte trigger-point
+	case a.parent.conf.Producer.Flush.Bytes > 0 && a.bufferBytes >= a.parent.conf.Producer.Flush.Bytes:
+		return true
+	default:
+		return false
+	}
+}
+
+func (a *aggregator) reset() {
+	a.timer = nil
+	a.buffer = nil
+	a.bufferBytes = 0
+}
+
 // takes a batch at a time from the aggregator and sends to the broker
 type flusher struct {
 	parent *asyncProducer

config.go

@@ -188,11 +188,11 @@ func (c *Config) Validate() error {
 	if c.Producer.RequiredAcks > 1 {
 		Logger.Println("Producer.RequiredAcks > 1 is deprecated and will raise an exception with kafka >= 0.8.2.0.")
 	}
-	if c.Producer.MaxMessageBytes >= forceFlushThreshold() {
-		Logger.Println("Producer.MaxMessageBytes is too close to MaxRequestSize; it will be ignored.")
+	if c.Producer.MaxMessageBytes >= int(MaxRequestSize) {
+		Logger.Println("Producer.MaxMessageBytes is larger than MaxRequestSize; it will be ignored.")
 	}
-	if c.Producer.Flush.Bytes >= forceFlushThreshold() {
-		Logger.Println("Producer.Flush.Bytes is too close to MaxRequestSize; it will be ignored.")
+	if c.Producer.Flush.Bytes >= int(MaxRequestSize) {
+		Logger.Println("Producer.Flush.Bytes is larger than MaxRequestSize; it will be ignored.")
 	}
 	if c.Producer.Timeout%time.Millisecond != 0 {
 		Logger.Println("Producer.Timeout only supports millisecond resolution; nanoseconds will be truncated.")