natsio/jetstream_pubsub.go

package natsio

import (
	"errors"
	"fmt"

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

// Publish ...
func (js JetStream) Publish(subject string, payload []byte) error {
	channel := combineStreamAndSubjectName(js.streamName, subject)

	_, err := js.instance.PublishAsync(channel, payload)
	if err != nil {
		msg := fmt.Sprintf("[NATS JETSTREAM] - publish message to subject #%s error: %s", channel, err.Error())
		return errors.New(msg)
	}
	return nil
}

// Subscribe ...
func (js JetStream) Subscribe(subject string, cb nats.MsgHandler) (*nats.Subscription, error) {
	channel := combineStreamAndSubjectName(js.streamName, subject)

	sub, err := js.instance.Subscribe(channel, cb)
	if err != nil {
		msg := fmt.Sprintf("[NATS JETSTREAM] - subscribe subject %s error: %s", channel, err.Error())
		return nil, errors.New(msg)
	}
	return sub, nil
}

// PullSubscribe ...
//
// Example:
//
// js := natsio.GetJetStream()
//
// sub, err := js.PullSubscribe("A_SUBJECT", "A_SUBJECT", "A_CONSUMER")
//
//	for {
//	  messages, err := sub.Fetch(10)
//	  // process each messages
//	}
func (js JetStream) PullSubscribe(subject, consumer string) (*nats.Subscription, error) {
	channel := combineStreamAndSubjectName(js.streamName, subject)

	// Check if consumer existed
	con, err := js.GetConsumerInfo(consumer)
	if con == nil || err != nil {
		msg := fmt.Sprintf("[NATS JETSTREAM] - pull subscribe consumer %s not existed in stream %s", consumer, js.streamName)
		return nil, errors.New(msg)
	}

	// Pull
	sub, err := js.instance.PullSubscribe(channel, consumer)
	if err != nil {
		msg := fmt.Sprintf("[NATS JETSTREAM] - pull subscribe subject #%s - consumer #%s error: %s", channel, consumer, err.Error())
		return nil, errors.New(msg)
	}

	return sub, nil
}