snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/real-world-examples/persistent-event-log/main.go

@@ -0,0 +1,149 @@
+package main
+
+import (
+	"context"
+	stdSQL "database/sql"
+	"encoding/json"
+	"log"
+	"time"
+
+	driver "github.com/go-sql-driver/mysql"
+
+	"github.com/ThreeDotsLabs/watermill"
+	"github.com/ThreeDotsLabs/watermill-googlecloud/v2/pkg/googlecloud"
+	"github.com/ThreeDotsLabs/watermill-sql/v4/pkg/sql"
+	"github.com/ThreeDotsLabs/watermill/message"
+	"github.com/ThreeDotsLabs/watermill/message/router/middleware"
+	"github.com/ThreeDotsLabs/watermill/message/router/plugin"
+)
+
+var (
+	logger           = watermill.NewStdLogger(false, false)
+	googleCloudTopic = "events"
+	mysqlTable       = "events"
+)
+
+type event struct {
+	Name       string `json:"name"`
+	OccurredAt string `json:"occurred_at"`
+}
+
+func main() {
+	router, err := message.NewRouter(message.RouterConfig{}, logger)
+	if err != nil {
+		panic(err)
+	}
+
+	router.AddPlugin(plugin.SignalsHandler)
+	router.AddMiddleware(middleware.Recoverer)
+
+	db := createDB()
+
+	subscriber := createSubscriber()
+	publisher := createPublisher(db)
+
+	go simulateEvents()
+
+	router.AddHandler(
+		"googlecloud-to-mysql",
+		googleCloudTopic,
+		subscriber,
+		mysqlTable,
+		publisher,
+		func(msg *message.Message) ([]*message.Message, error) {
+			consumedEvent := event{}
+			err := json.Unmarshal(msg.Payload, &consumedEvent)
+			if err != nil {
+				return nil, err
+			}
+
+			log.Printf("received event %+v with UUID %s", consumedEvent, msg.UUID)
+
+			return []*message.Message{msg}, nil
+		},
+	)
+
+	if err := router.Run(context.Background()); err != nil {
+		panic(err)
+	}
+}
+
+func createDB() *stdSQL.DB {
+	conf := driver.NewConfig()
+	conf.Net = "tcp"
+	conf.User = "root"
+	conf.Addr = "mysql"
+	conf.DBName = "watermill"
+
+	db, err := stdSQL.Open("mysql", conf.FormatDSN())
+	if err != nil {
+		panic(err)
+	}
+
+	err = db.Ping()
+	if err != nil {
+		panic(err)
+	}
+
+	return db
+}
+
+func createSubscriber() message.Subscriber {
+	sub, err := googlecloud.NewSubscriber(
+		googlecloud.SubscriberConfig{
+			ProjectID: "example",
+		},
+		logger,
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	return sub
+}
+
+func createPublisher(db *stdSQL.DB) message.Publisher {
+	pub, err := sql.NewPublisher(
+		sql.BeginnerFromStdSQL(db),
+		sql.PublisherConfig{
+			SchemaAdapter:        sql.DefaultMySQLSchema{},
+			AutoInitializeSchema: true,
+		},
+		logger,
+	)
+	if err != nil {
+		panic(err)
+	}
+
+	return pub
+}
+
+func simulateEvents() {
+	pub, err := googlecloud.NewPublisher(googlecloud.PublisherConfig{
+		ProjectID: "example",
+	}, logger)
+	if err != nil {
+		panic(err)
+	}
+
+	for {
+		e := event{
+			Name:       "UserSignedUp",
+			OccurredAt: time.Now().UTC().Format(time.RFC3339),
+		}
+		payload, err := json.Marshal(e)
+		if err != nil {
+			panic(err)
+		}
+
+		err = pub.Publish(googleCloudTopic, message.NewMessage(
+			watermill.NewUUID(),
+			payload,
+		))
+		if err != nil {
+			panic(err)
+		}
+
+		time.Sleep(time.Second)
+	}
+}