Context
Event Grid first validates that a webhook endpoint is willing to receive a subscription. Only then can ordinary event delivery begin. A subscription creation failure and a missing business event are different stages, even when both involve the same URL.
Prerequisites are the event source, subscription provisioning state, event schema, endpoint URL and sanitized HTTP logs. Obtain read access to filters, retry settings and any dead-letter destination. Use an approved test event with a unique identifier and a reversible business effect.
1. Confirm the validation handshake
Check the configured schema before changing endpoint code. With Event Grid schema, a custom handler must participate in the subscription validation handshake and return the expected validation response. CloudEvents uses its documented abuse-protection handshake, including HTTP OPTIONS behavior, rather than the same JSON event exchange.
Inspect the endpoint's actual status, response body and timing during validation. A WAF, authentication gateway or redirect can prevent the handler from receiving the request. A generic successful response is insufficient if the required validation content is absent. Review certificate trust and avoid self-signed endpoint certificates for this supported workflow.
2. Trace a matching event
After provisioning succeeds, verify event type, subject filters and advanced filters against the actual event envelope. An event published successfully is not proof that it matched this subscription. Preserve its identifier and publication time for correlation.
Inspect delivery attempts and the webhook's response. Event Grid interprets supported success status codes as acknowledgement, not evidence that a database update later completed. A handler that accepts work asynchronously should first put it into a durable internal queue and maintain its own completion tracking. Avoid returning success before the event is safely owned.
3. Review retries and terminal outcomes
Read retry limits, event lifetime and dead-letter configuration. Some response classes indicate a permanent configuration problem rather than a useful retry. Use the current endpoint-specific documentation when classifying statuses. Do not assume every failure will remain available indefinitely.
Check that the dead-letter storage destination exists and is usable by the delivery path. Dead-lettering is not enabled automatically for every subscription. Reconcile failed event IDs with business processing before replay. Delivery is at least once and order is not guaranteed, so the handler must tolerate duplicates and out-of-order events.
Diagnostic checkpoints
| Symptom | Likely stage | Next evidence |
|---|---|---|
| Subscription creation fails | Endpoint validation | Schema and handshake response |
| Subscription ready, no attempt | Event matching | Type and filter comparison |
| HTTP success, no business update | Handler ownership | Durable queue and completion |
| Failed event cannot be found | Terminal handling | Lifetime and dead-letter setup |
Illustrative scenario
A hypothetical webhook returns 202 for every request, including an Event Grid schema validation event. Its ordinary asynchronous design seems healthy, but the validation handshake requires the documented synchronous response. After fixing validation, the team separately verifies durable event acceptance. This example is illustrative and reports no real customer delivery result.
Verification and event SOP
Verify subscription creation, one matching test event, its durable acceptance and its final business result. Test a harmless duplicate against the handler. In a nonproduction environment, exercise a controlled failure and confirm the intended terminal record.
Document schema, validation ownership, filters and replay criteria in the SOP. Monitor delivery failures and handler completion gaps separately. Recheck validation after WAF or authentication changes, and review dead-letter accessibility before a new event source begins producing business-critical notifications.
Explore Clouvenix cloud architecture for implementation and operational handover.
Technical reference
Validation troubleshooting, delivery and retry, and Event Grid schema handshake.