Service Bus messaging

Queue or topic

Use a queue when competing workers should process each message once. Use a topic when several consumers each need their own copy through separate subscriptions.

Settle peek-lock messages

Complete removes a successful message. Abandon releases it for delivery again. Defer keeps it aside until code receives it by sequence number. Dead-letter moves a message that should not be retried into the dead-letter queue.

For long handlers, renew the message lock before it expires. Otherwise the same message can be delivered again and its delivery count rises.

Filter subscriptions

A new subscription starts with a True filter, so it receives every topic message. Use a SQL filter for conditions on properties and a correlation filter for efficient equality matching. A rule action can change properties on the copy delivered to that subscription.

Inspect failures separately

Every queue and every subscription has its own dead-letter subqueue. Automatic failures can move messages there after the maximum delivery count, while application code can dead-letter immediately with a reason.