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

internal/publisher/retry.go

@@ -0,0 +1,108 @@
+package publisher
+
+import (
+	"time"
+
+	"github.com/ThreeDotsLabs/watermill"
+	"github.com/ThreeDotsLabs/watermill/message"
+
+	"github.com/pkg/errors"
+)
+
+var (
+	ErrNonPositiveNumberOfRetries  = errors.New("number of retries should be positive")
+	ErrNonPositiveTimeToFirstRetry = errors.New("time to first retry should be positive")
+)
+
+type RetryPublisherConfig struct {
+	MaxRetries int
+	// each subsequent retry doubles the time to next retry.
+	TimeToFirstRetry time.Duration
+	Logger           watermill.LoggerAdapter
+}
+
+func (c *RetryPublisherConfig) setDefaults() {
+	if c.MaxRetries == 0 {
+		c.MaxRetries = 5
+	}
+
+	if c.TimeToFirstRetry == 0 {
+		c.TimeToFirstRetry = time.Second
+	}
+
+	if c.Logger == nil {
+		c.Logger = watermill.NopLogger{}
+	}
+}
+
+func (c RetryPublisherConfig) validate() error {
+	if c.MaxRetries <= 0 {
+		return ErrNonPositiveNumberOfRetries
+	}
+	if c.TimeToFirstRetry <= 0 {
+		return ErrNonPositiveTimeToFirstRetry
+	}
+
+	return nil
+}
+
+// RetryPublisher is a decorator for a publisher that retries message publishing after a failure.
+type RetryPublisher struct {
+	pub    message.Publisher
+	config RetryPublisherConfig
+}
+
+func NewRetryPublisher(pub message.Publisher, config RetryPublisherConfig) (*RetryPublisher, error) {
+	config.setDefaults()
+
+	if err := config.validate(); err != nil {
+		return nil, errors.Wrap(err, "invalid RetryPublisher config")
+	}
+
+	return &RetryPublisher{
+		pub,
+		config,
+	}, nil
+}
+
+func (p RetryPublisher) Publish(topic string, messages ...*message.Message) error {
+	failedMessages := NewErrCouldNotPublish()
+
+	// todo: do some parallel processing maybe? this is a very basic implementation
+	for _, msg := range messages {
+		err := p.send(topic, msg)
+		if err != nil {
+			failedMessages.addMsg(msg, err)
+		}
+	}
+
+	if failedMessages.Len() > 0 {
+		return failedMessages
+	}
+
+	return nil
+}
+
+func (p RetryPublisher) Close() error {
+	return p.pub.Close()
+}
+
+// send sends one message at a time to prevent sending a successful message more than once.
+func (p RetryPublisher) send(topic string, msg *message.Message) error {
+	var err error
+	timeToNextRetry := p.config.TimeToFirstRetry
+
+	for i := 0; i < p.config.MaxRetries; i++ {
+		err = p.pub.Publish(topic, msg)
+		if err == nil {
+			return nil
+		}
+
+		p.config.Logger.Info("Publish failed, retrying in "+timeToNextRetry.String(), watermill.LogFields{
+			"error": err,
+		})
+		time.Sleep(timeToNextRetry)
+		timeToNextRetry *= 2
+	}
+	return err
+}