All deliveries to one destination failing at once
This page covers what “all deliveries to one destination failing at once” usually means and how to recover.
Symptoms
Section titled “Symptoms”- DLQ depth suddenly jumps for one destination.
- Harbor-Signature verification works in test but fails in prod.
What usually causes it
Section titled “What usually causes it”- Customer’s origin returned a maintenance page (5xx HTML) that your receiver treats as ‘unknown error’.
- TLS certificate expired on the customer’s destination URL.
- DNS change routing traffic to a placeholder.
- Circuit breaker tripped — Harbor auto-paused the destination.
How to fix
Section titled “How to fix”- Check the destination’s status in the dashboard. If ‘paused’, the circuit breaker tripped.
- Look at the last successful delivery’s response body to compare against current failures.
- Run a manual curl against the destination URL from outside your network.
- Once the customer confirms their side is healthy, un-pause and use replay-dlq to catch up.