Add new publisher for Google Pub Sub.

cmd/wal-listener/init.go

@@ -52,7 +52,7 @@ type eventPublisher interface {
 }
 
 // factoryPublisher represents a factory function for creating a eventPublisher.
-func factoryPublisher(cfg *config.PublisherCfg, logger *slog.Logger) (eventPublisher, error) {
+func factoryPublisher(ctx context.Context, cfg *config.PublisherCfg, logger *slog.Logger) (eventPublisher, error) {
 	switch cfg.Type {
 	case config.PublisherTypeKafka:
 		producer, err := publisher.NewProducer(cfg)
@@ -94,6 +94,14 @@ func factoryPublisher(cfg *config.PublisherCfg, logger *slog.Logger) (eventPubli
 		}
 
 		return pub, nil
+	case config.PublisherTypeGooglePubSub:
+		pubSubConn, err := publisher.NewPubSubConnection(ctx, logger, cfg.PubSubProjectID)
+		if err != nil {
+			return nil, fmt.Errorf("could not create pubsub connection: %w", err)
+		}
+
+		pubSubPublisher := publisher.NewGooglePubSubPublisher(pubSubConn)
+		return pubSubPublisher, nil
 	default:
 		return nil, fmt.Errorf("unknown publisher type: %s", cfg.Type)
 	}

cmd/wal-listener/main.go

@@ -57,7 +57,7 @@ func main() {
 				return fmt.Errorf("pgx connection: %w", err)
 			}
 
-			pub, err := factoryPublisher(cfg.Publisher, logger)
+			pub, err := factoryPublisher(c.Context, cfg.Publisher, logger)
 			if err != nil {
 				return fmt.Errorf("factory publisher: %w", err)
 			}

config/config.go

@@ -13,9 +13,10 @@ import (
 type PublisherType string
 
 const (
-	PublisherTypeNats     PublisherType = "nats"
-	PublisherTypeKafka    PublisherType = "kafka"
-	PublisherTypeRabbitMQ PublisherType = "rabbitmq"
+	PublisherTypeNats         PublisherType = "nats"
+	PublisherTypeKafka        PublisherType = "kafka"
+	PublisherTypeRabbitMQ     PublisherType = "rabbitmq"
+	PublisherTypeGooglePubSub PublisherType = "googlepubsub"
 )
 
 // Config for wal-listener.
@@ -39,14 +40,15 @@ type ListenerCfg struct {
 
 // PublisherCfg represent configuration for any types publisher.
 type PublisherCfg struct {
-	Type        PublisherType `valid:"required"`
-	Address     string        `valid:"required"`
-	Topic       string        `valid:"required"`
-	TopicPrefix string
-	EnableTLS   bool   `json:"enable_tls"`
-	ClientCert  string `json:"client_cert"`
-	ClientKey   string `json:"client_key"`
-	CACert      string `json:"ca_cert"`
+	Type            PublisherType `valid:"required"`
+	Address         string
+	Topic           string `valid:"required"`
+	TopicPrefix     string
+	EnableTLS       bool   `json:"enable_tls"`
+	ClientCert      string `json:"client_cert"`
+	ClientKey       string `json:"client_key"`
+	CACert          string `json:"ca_cert"`
+	PubSubProjectID string
 }
 
 // DatabaseCfg path of the PostgreSQL DB config.

publisher/pubsub.go

@@ -0,0 +1,30 @@
+package publisher
+
+import (
+	"context"
+	"github.com/goccy/go-json"
+)
+
+type GooglePubSubPublisher struct {
+	pubSubConnection *PubSubConnection
+}
+
+func NewGooglePubSubPublisher(pubSubConnection *PubSubConnection) *GooglePubSubPublisher {
+	return &GooglePubSubPublisher{
+		pubSubConnection,
+	}
+}
+
+// Publish send events, implements eventPublisher.
+func (p *GooglePubSubPublisher) Publish(ctx context.Context, topic string, event Event) error {
+	body, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+
+	return p.pubSubConnection.Publish(ctx, topic, body)
+}
+
+func (p *GooglePubSubPublisher) Close() error {
+	return p.pubSubConnection.Close()
+}

publisher/pubsubconnection.go

@@ -0,0 +1,79 @@
+package publisher
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"sync"
+
+	"cloud.google.com/go/pubsub"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+type PubSubConnection struct {
+	logger    *slog.Logger
+	client    *pubsub.Client
+	projectID string
+	topics    map[string]*pubsub.Topic
+	mu        sync.RWMutex
+}
+
+func NewPubSubConnection(ctx context.Context, logger *slog.Logger, pubSubProjectId string) (*PubSubConnection, error) {
+	if pubSubProjectId == "" {
+		return nil, fmt.Errorf("project id is required for pub sub connection")
+	}
+
+	c, err := pubsub.NewClient(ctx, pubSubProjectId)
+	if err != nil {
+		return nil, err
+	}
+	return &PubSubConnection{
+		logger:    logger,
+		client:    c,
+		projectID: pubSubProjectId,
+		topics:    make(map[string]*pubsub.Topic),
+		mu:        sync.RWMutex{},
+	}, nil
+}
+
+func (c *PubSubConnection) getTopic(topic string) *pubsub.Topic {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if top, ok := c.topics[topic]; ok {
+		return top
+	}
+
+	t := c.client.TopicInProject(topic, c.projectID)
+	t.PublishSettings.NumGoroutines = 1
+	t.PublishSettings.CountThreshold = 1
+	c.topics[topic] = t
+	return t
+}
+
+func (c *PubSubConnection) Publish(ctx context.Context, topic string, data []byte) error {
+	t := c.getTopic(topic)
+	defer t.Flush()
+
+	var res *pubsub.PublishResult
+	var err error
+	res = t.Publish(ctx, &pubsub.Message{
+		Data: data,
+	})
+
+	_, err = res.Get(ctx)
+	if err != nil {
+		c.logger.Error("Failed to publish message", "err", err)
+		if status.Code(err) == codes.NotFound {
+			return fmt.Errorf("topic not found %w", err)
+		} else {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (c *PubSubConnection) Close() error {
+	return c.client.Close()
+}