[QUESTION] - Is it possible to Start, Stop, Pause, Resume consumer?

[sujit-baniya]

I was wondering if I can Start/Stop, Resume/Pause the consumer on demand?

For e.g.

package main

import (
	"context"
	"fmt"
	"runtime"
	"time"
	
	"github.com/nats-io/nats.go"
	"github.com/nats-io/nats.go/jetstream"
)

func main() {
	nc, _ := nats.Connect(nats.DefaultURL)
	js, _ := jetstream.New(nc)
	cfg := jetstream.StreamConfig{
		Name:      "EVENTS",
		Retention: jetstream.WorkQueuePolicy,
		Subjects:  []string{"events.>"},
	}
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	
	stream, err := js.Stream(ctx, "EVENTS")
	if err != nil || stream == nil {
		stream, err = js.CreateStream(ctx, cfg)
		if err != nil {
			panic(err)
		}
		fmt.Println("created the stream")
	}
	cons, err := stream.CreateOrUpdateConsumer(ctx, jetstream.ConsumerConfig{
		Name:          "processor-us",
		FilterSubject: "events.>",
	})
	if err != nil {
		panic(err)
	}
	cons.Consume(func(msg jetstream.Msg) {
		fmt.Printf("eu sub got: %s\n", msg.Subject())
		msg.Ack()
	})
        // cons.Pause()
        // cons.Resume()
        // cons.Stop()
	runtime.Goexit()
}

[Jarema]

There is Stop and StopAfter(int), but currently we do not have Pause and Resume.

[jnmoyne]

You should use Messages() instead of Consume() that way when you want to pause you simply stop calling it in a loop and when you want to resume you start that loop again.

[jnmoyne]

Note that the ability to pause/resume consumers will be available as part of the nats server version 2.11 and above

(see: nats-io/nats-architecture-and-design#266)