[ADDED] Ability to set a queue group for stan-bench

You can now specify `-qgroup` to specify a queue group.
Note that since the number of messages expected is for the whole
group, then the first member to make the total number of
received messages reach the goal, it will emit a new message to
make all other members break out of their loop.

Resolves #200

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

examples/stan-bench/main.go

@@ -20,6 +20,7 @@ import (
 	"log"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/nats-io/go-nats"
@@ -40,10 +41,14 @@ const (
 )
 
 func usage() {
-	log.Fatalf("Usage: stan-bench [-s server (%s)] [-tls] [-c CLUSTER_ID] [-id CLIENT_ID] [-np NUM_PUBLISHERS] [-ns NUM_SUBSCRIBERS] [-n NUM_MSGS] [-ms MESSAGE_SIZE] [-csv csvfile] [-mpa MAX_NUMBER_OF_PUBLISHED_ACKS_INFLIGHT] [-io] [-a] <subject>\n", nats.DefaultURL)
+	log.Fatalf("Usage: stan-bench [-s server (%s)] [-tls] [-c CLUSTER_ID] [-id CLIENT_ID] [-qgroup QUEUE_GROUP_NAME] [-np NUM_PUBLISHERS] [-ns NUM_SUBSCRIBERS] [-n NUM_MSGS] [-ms MESSAGE_SIZE] [-csv csvfile] [-mpa MAX_NUMBER_OF_PUBLISHED_ACKS_INFLIGHT] [-io] [-a] <subject>\n", nats.DefaultURL)
 }
 
-var benchmark *bench.Benchmark
+var (
+	benchmark  *bench.Benchmark
+	qTotalRecv int32
+	qSubsLeft  int32
+)
 
 func main() {
 	var clusterID string
@@ -61,6 +66,7 @@ func main() {
 	var maxPubAcks = flag.Int("mpa", DefaultMaxPubAcksInflight, "Max number of published acks in flight")
 	var clientID = flag.String("id", DefaultClientID, "Benchmark process base client ID")
 	var csvFile = flag.String("csv", "", "Save bench data to csv file")
+	var queue = flag.String("qgroup", "", "Queue group name")
 
 	log.SetFlags(0)
 	flag.Usage = usage
@@ -87,11 +93,14 @@ func main() {
 
 	donewg.Add(*numPubs + *numSubs)
 
+	if *queue != "" {
+		qSubsLeft = int32(*numSubs)
+	}
 	// Run Subscribers first
 	startwg.Add(*numSubs)
 	for i := 0; i < *numSubs; i++ {
 		subID := fmt.Sprintf("%s-sub-%d", *clientID, i)
-		go runSubscriber(&startwg, &donewg, opts, clusterID, *numMsgs, *messageSize, *ignoreOld, subID)
+		go runSubscriber(&startwg, &donewg, opts, clusterID, subID, *queue, *numMsgs, *messageSize, *ignoreOld)
 	}
 	startwg.Wait()
 
@@ -177,7 +186,7 @@ func runPublisher(startwg, donewg *sync.WaitGroup, opts nats.Options, clusterID
 	donewg.Done()
 }
 
-func runSubscriber(startwg, donewg *sync.WaitGroup, opts nats.Options, clusterID string, numMsgs int, msgSize int, ignoreOld bool, subID string) {
+func runSubscriber(startwg, donewg *sync.WaitGroup, opts nats.Options, clusterID, subID, queue string, numMsgs, msgSize int, ignoreOld bool) {
 	nc, err := opts.Connect()
 	if err != nil {
 		log.Fatalf("Subscriber %s can't connect: %v\n", subID, err)
@@ -194,27 +203,48 @@ func runSubscriber(startwg, donewg *sync.WaitGroup, opts nats.Options, clusterID
 	subj := args[0]
 	ch := make(chan time.Time, 2)
 
+	isQueue := queue != ""
 	received := 0
 	mcb := func(msg *stan.Msg) {
 		received++
 		if received == 1 {
 			ch <- time.Now()
 		}
-		if received >= numMsgs {
-			ch <- time.Now()
+		if isQueue {
+			if atomic.AddInt32(&qTotalRecv, 1) >= int32(numMsgs) {
+				ch <- time.Now()
+			}
+		} else {
+			if received >= numMsgs {
+				ch <- time.Now()
+			}
 		}
 	}
 
+	var sub stan.Subscription
 	if ignoreOld {
-		snc.Subscribe(subj, mcb)
+		sub, err = snc.QueueSubscribe(subj, queue, mcb)
 	} else {
-		snc.Subscribe(subj, mcb, stan.DeliverAllAvailable())
+		sub, err = snc.QueueSubscribe(subj, queue, mcb, stan.DeliverAllAvailable())
+	}
+	if err != nil {
+		log.Fatalf("Subscriber %s can't subscribe: %v", subID, err)
 	}
 	startwg.Done()
 
 	start := <-ch
 	end := <-ch
-	benchmark.AddSubSample(bench.NewSample(numMsgs, msgSize, start, end, snc.NatsConn()))
+	benchmark.AddSubSample(bench.NewSample(received, msgSize, start, end, snc.NatsConn()))
+	// For queues, since not each member receives the total number of messages,
+	// when a member is done, it needs to publish a message to unblock other member(s).
+	if isQueue {
+		if sr := atomic.AddInt32(&qSubsLeft, -1); sr > 0 {
+			// Close this queue member first so that there is no chance that the
+			// server sends the message we are going to publish back to this member.
+			sub.Close()
+			snc.Publish(subj, []byte("done"))
+		}
+	}
 	snc.Close()
 	nc.Close()
 	donewg.Done()