Message payload (#12)

Added an option to specify message payload

README.md

@@ -30,6 +30,8 @@ Usage of ./mqtt-benchmark:
     	Output format: text|json (default "text")
   -password string
     	MQTT client password (empty if auth disabled)
+  -payload string
+    	MQTT message payload. If empty, then payload is generated based on the size parameter
   -qos int
     	QoS for published messages (default 1)
   -quiet
@@ -75,6 +77,33 @@ Average Bandwidth (msg/sec): 6.761
 Total Bandwidth (msg/sec):   676.112
 ```
 
+With payload specified:
+
+```sh
+> mqtt-benchmark --broker tcp://broker.local:1883 --count 100 --clients 10 --qos 1 --topic house/bedroom/temperature --payload {\"temperature\":20,\"timeStamp\":1597314150}
+....
+
+======= CLIENT 0 =======
+Ratio:               1.000 (100/100)
+Runtime (s):         0.725
+Msg time min (ms):   1.999
+Msg time max (ms):   22.997
+Msg time mean (ms):  6.955
+Msg time std (ms):   3.523
+Bandwidth (msg/sec): 137.839
+
+========= TOTAL (1) =========
+Total Ratio:                 1.000 (100/100)
+Total Runtime (sec):         0.736
+Average Runtime (sec):       0.725
+Msg time min (ms):           1.999
+Msg time max (ms):           22.997
+Msg time mean mean (ms):     6.955
+Msg time mean std (ms):      0.000
+Average Bandwidth (msg/sec): 137.839
+Total Bandwidth (msg/sec):   137.839
+```
+
 Similarly, in JSON:
 
 ```json

client.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/GaryBoone/GoStats/stats"
+
 	mqtt "github.com/eclipse/paho.mqtt.golang"
 )
 
@@ -18,6 +19,7 @@ type Client struct {
 	BrokerUser  string
 	BrokerPass  string
 	MsgTopic    string
+  MsgPayload string
 	MsgSize     int
 	MsgCount    int
 	MsgQoS      byte
@@ -74,13 +76,20 @@ func (c *Client) Run(res chan *RunResults) {
 }
 
 func (c *Client) genMessages(ch chan *Message, done chan bool) {
-	for i := 0; i < c.MsgCount; i++ {
+	var payload interface{}
+  // set payload if specified
+  if c.MsgPayload != "" {
+    payload = c.MsgPayload
+  } else {
+    payload = make([]byte, c.MsgSize)
+  }
+
   ch <- &Message{
     Topic:   c.MsgTopic,
     QoS:     c.MsgQoS,
-			Payload: make([]byte, c.MsgSize),
-		}
+    Payload: payload,
   }
+
 	done <- true
 	// log.Printf("CLIENT %v is done generating messages\n", c.ID)
 	return

main.go

@@ -60,6 +60,7 @@ func main() {
 	var (
 		broker       = flag.String("broker", "tcp://localhost:1883", "MQTT broker endpoint as scheme://host:port")
 		topic        = flag.String("topic", "/test", "MQTT topic for outgoing messages")
+    payload      = flag.String("payload", "", "MQTT message payload. If empty, then payload is generated based on the size parameter")
 		username     = flag.String("username", "", "MQTT client username (empty if auth disabled)")
 		password     = flag.String("password", "", "MQTT client password (empty if auth disabled)")
 		qos          = flag.Int("qos", 1, "QoS for published messages")
@@ -109,6 +110,7 @@ func main() {
 			BrokerUser:  *username,
 			BrokerPass:  *password,
 			MsgTopic:    *topic,
+      MsgPayload:  *payload,
 			MsgSize:     *size,
 			MsgCount:    *count,
 			MsgQoS:      byte(*qos),