messagepush.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/cloud"
	"google.golang.org/cloud/pubsub"
)

const (
	projectID = "ecorson-drud"
	jwtPath   = "/path/to/your/jwt.json"
	topicName = "topic_test"
	subName   = "topic_test"
	numMsgs   = 5
)

func main() {
	// read contents of jwt file
	jbytes, err := ioutil.ReadFile(jwtPath)
	if err != nil {
		log.Fatalln(err)
	}
	// instantiate googel conf using jwt contents
	conf, err := google.JWTConfigFromJSON(
		jbytes,
		pubsub.ScopeCloudPlatform,
		pubsub.ScopePubSub,
	)
	if err != nil {
		log.Fatalln(err)
	}

	// create a google cloud context
	googleCTX := cloud.NewContext(projectID, conf.Client(oauth2.NoContext))

	// instantiate a client for workign with pub sub
	client, err := pubsub.NewClient(googleCTX, projectID, cloud.WithTokenSource(conf.TokenSource(googleCTX)))
	if err != nil {
		log.Fatalln(err)
	}

	// get topic, create it if it does not exist
	exists, err := pubsub.TopicExists(googleCTX, topicName)
	if err != nil {
		log.Fatalln(err)
	}

	var topic *pubsub.Topic
	if exists {
		topic = client.Topic(topicName)
	} else {
		topic, err = client.NewTopic(googleCTX, topicName)
		if err != nil {
			log.Fatalln(err)
		}
	}

	// publish 5 messages to the topic
	for i := range []int{1, 2, 3, 4, 5} {
		atts := map[string]string{
			"channel": "kube-alerts",
		}
		if i == 2 {
			atts["severity"] = "warn"

		} else if i == 3 {
			atts["severity"] = "debug"
		} else if i == 4 {
			atts["severity"] = "fatal"
		} else {
			atts["severity"] = "good"
		}
		msgID, err := topic.Publish(googleCTX, &pubsub.Message{
			Data:       []byte(fmt.Sprintf("message %d", i)),
			Attributes: atts,
		})
		if err != nil {
			log.Fatalln(err)
		}

		log.Println("New message id:", msgID)
	}

}