a cmdline nats client

nats.go

package main

import (
	"flag"
	"log"
	"time"

	"github.com/nats-io/go-nats"
)

func main() {
	var publish, reply_to, request_reply, subscribe, queue string
	count := 1
	var timeout time.Duration
	flag.StringVar(&publish, "publish", "", "the channel on which to publish a message")
	flag.StringVar(&reply_to, "reply_to", "", "the channel on which to publish a message w/reply_to")
	flag.StringVar(&request_reply, "request_reply", "", "the channel on which to request a reply")
	flag.StringVar(&subscribe, "subscribe", "", "the channel on which to subscribe for messages")
	flag.StringVar(&queue, "queue", "", "the queue on which to subscribe or send")
	flag.IntVar(&count, "count", 1, "the number of messages to receive")
	flag.DurationVar(&timeout, "timeout", 100*time.Millisecond, "how long to wait to send or receive a single message")
	flag.Parse()
	nc, err := nats.Connect(nats.DefaultURL)
	if err != nil {
		log.Fatal(err)
	}
	defer nc.Flush()
	defer nc.Close()

	if publish != "" {
		if err := nc.Publish(publish, []byte(flag.Arg(0))); err != nil {
			log.Fatal(err)
		}

	}

	if reply_to != "" {
		uniqueReplyTo := nats.NewInbox()
		sub, err := nc.SubscribeSync(uniqueReplyTo)
		if err != nil {
			log.Fatal(err)
		}
		if err := nc.PublishRequest(publish, uniqueReplyTo, []byte(flag.Arg(0))); err != nil {
			log.Fatal(err)
		}
		msg, err := sub.NextMsg(timeout)
		if err != nil {
			log.Fatal(err)
		}
		log.Printf("Reply: %s", msg.Data)
	}

	if request_reply != "" {
		msg, err := nc.Request(request_reply, []byte(flag.Arg(0)), timeout)
		if err != nil {
			log.Fatal(err)
		}
		log.Printf("Reply: %s", msg.Data)
	}

	if subscribe != "" {
		var err error
		var sub *nats.Subscription
		if queue != "" {
			sub, err = nc.QueueSubscribeSync(subscribe, queue)
		} else {
			sub, err = nc.SubscribeSync(subscribe)
		}
		if err != nil {
			log.Fatal(err)
		}
		for i := 0; i < count; i++ {
			msg, err := sub.NextMsg(timeout)
			if err != nil {
				log.Fatal(err)
			}
			log.Printf("Reply: %s", msg.Data)
		}
	}
}