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

message/router/middleware/delay_on_error.go

@@ -0,0 +1,47 @@
+package middleware
+
+import (
+	"time"
+
+	"github.com/ThreeDotsLabs/watermill/components/delay"
+	"github.com/ThreeDotsLabs/watermill/message"
+)
+
+// DelayOnError is a middleware that adds the delay metadata to the message if an error occurs.
+//
+// IMPORTANT: The delay metadata doesn't cause delays with all Pub/Subs! Using it won't have any effect on Pub/Subs that don't support it.
+// See the list of supported Pub/Subs in the documentation: https://watermill.io/advanced/delayed-messages/
+type DelayOnError struct {
+	// InitialInterval is the first interval between retries. Subsequent intervals will be scaled by Multiplier.
+	InitialInterval time.Duration
+	// MaxInterval sets the limit for the exponential backoff of retries. The interval will not be increased beyond MaxInterval.
+	MaxInterval time.Duration
+	// Multiplier is the factor by which the waiting interval will be multiplied between retries.
+	Multiplier float64
+}
+
+func (d *DelayOnError) Middleware(h message.HandlerFunc) message.HandlerFunc {
+	return func(msg *message.Message) ([]*message.Message, error) {
+		msgs, err := h(msg)
+		if err != nil {
+			d.applyDelay(msg)
+		}
+
+		return msgs, err
+	}
+}
+
+func (d *DelayOnError) applyDelay(msg *message.Message) {
+	delayedForStr := msg.Metadata.Get(delay.DelayedForKey)
+	delayedFor, err := time.ParseDuration(delayedForStr)
+	if delayedForStr != "" && err == nil {
+		delayedFor *= time.Duration(d.Multiplier)
+		if delayedFor > d.MaxInterval {
+			delayedFor = d.MaxInterval
+		}
+
+		delay.Message(msg, delay.For(delayedFor))
+	} else {
+		delay.Message(msg, delay.For(d.InitialInterval))
+	}
+}