Event Grid Dead-Letter Reprocessing

Overview

This solution provides resilient recovery for failed Azure Event Grid deliveries. When Event Grid exhausts its own delivery retries, it dead-letters the undeliverable events to a Blob Storage container - where they are typically forgotten. This solution automatically picks them up, republishes them to the original topic (reprocessing), archives the handled blob, and escalates persistent failures to engineering in Microsoft Teams with the payload.

It ships as one solution containing two cooperating flows: an Event Trigger flow that fires the moment a dead-letter blob is written, and a Scheduled Sweep flow that hourly lists the container and reprocesses anything the event-driven flow missed.

Both flows ship Off (demo).

Use Case

An event-driven system (Event Grid topics/subscriptions feeding webhooks, Functions, Logic Apps, etc.) needs a safety net for events that failed delivery. Rather than silently losing dead-lettered events, this solution recovers them automatically and surfaces the ones that genuinely cannot be recovered so engineers can intervene with the full payload in hand.

Flow Architecture

Environment Variables

Connectors & Connections

Note — All connections are referenced as solution connection references; the flow is portable between environments as long as a connection is mapped at import time.

Customization Guide

Almost every realistic variant of this flow can be implemented by changing environment variable values. A few cases require small edits inside the flow definition — those are called out explicitly below.

Reprocess target

Republishing to the topic re-delivers to all subscribers. To replay to a single handler, point the republish action at the handler's endpoint.

Exhaustion policy

Tune the max delivery attempts, or add exponential backoff before re-republishing.

Sweep cadence

Change the Recurrence on the sweep flow (default hourly).

Audit trail

Add a Dataverse CreateRecord alongside each Teams notification to persist a reprocessing log keyed on the correlation id.

Metrics

Track dead-letter container depth over time from the ListFolder_V4 output.

Key Expressions

The flow is intentionally light on Power Fx / WDL gymnastics — the heaviest expressions are the branch-name concatenation and the approval outcome check. They are listed below in the order they appear in the flow.

startsWith(outputs('Compose_BlobSubject'), concat('/blobServices/default/containers/', variables('varDeadLetterContainer'), '/'))

int(coalesce(first(body('Parse_DeadLetter_Events'))?['deliveryAttempts'], first(body('Parse_DeadLetter_Events'))?['deliveryCount'], '0'))

@greaterOrEquals(outputs('Compose_FirstDeliveryAttempts'), variables('varMaxAttempts'))