fix(destregistry): treat event format errors as failed deliveries, not DLQ#957
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…t DLQ A Format/key-template failure (e.g. an S3 key_template referencing a field absent from the event) returned a nil delivery, which the registry turned into a nil attempt and the deliverymq handler classified as a PreDeliveryError → nack → Pub/Sub DLQ. The failure was never logged, invisible to the customer, and paged us instead of surfacing as an actionable delivery error. Add destregistry.NewFormatErrorDelivery, returning a non-nil failed Delivery plus an ErrDestinationPublishAttempt, so the registry records a failed attempt, acks the message, and retries via the scheduler. The customer-facing response is a generic message; the raw Go error stays on the error for logs/telemetry and is not persisted on the attempt. Apply it across all providers with a Format step: s3, sqs, azure_servicebus, gcp_pubsub, webhook, webhook_standard (previously `return nil, err`) and kinesis, kafka (previously nil-delivery ErrDestinationPublishAttempt). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…ot DLQ Standalone e2e test reproducing the production incident: an aws_s3 destination whose key_template references a field missing from the event. Asserts the fixed behavior end to end — nothing is written to S3, each delivery is recorded as a failed attempt carrying the format error, and retries run on the normal schedule and exhaust their budget rather than being nacked/dead-lettered. Verified as a real guard: reverting the destawss3 fix makes this test fail (0 attempts logged, message dead-lettered) instead of recording 3 attempts. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The helper returns the (*Delivery, error) pair a publisher returns on a format failure, not just a delivery — name it accordingly. Behavior unchanged. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
alexbouchardd
approved these changes
Jun 16, 2026
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Problem
When a destination fails to format a specific event (e.g. an
aws_s3key_templatereferencing a field that event doesn't have), the pipeline treated it as a system error: the message was retried blindly and eventually dead-lettered. The failure was never recorded, was invisible to the customer, and paged us — instead of being handled like any other failed delivery.What this changes
A formatting failure is now treated as a normal failed delivery: it's recorded as a failed attempt the customer can see, and it retries on the normal schedule until exhausted. No silent dead-lettering, no page.
Applied across all destination types that format events per-event.
Tests
Unit coverage plus an e2e regression (
cmd/e2e/regression_format_error_test.go) that forces a format failure and asserts it's recorded as failed attempts and exhausts retries without being dead-lettered.🤖 Generated with Claude Code