Reconsume

Reconsume is the act of processing a data item, such as a message, more than once. In computing and data pipelines, reconsume refers to the re-delivery and re-processing of items that were not successfully handled on a prior attempt. The objective is to maintain reliability in the face of transient failures, but reprocessing introduces the possibility of duplicate work if handlers are not idempotent.

In message brokers and streaming systems, consumers acknowledge messages to confirm successful handling. If a message is not acknowledged, or a negative acknowledgement is issued, the system may requeue or redeliver the item to the same or a different consumer. Reconsume can also occur when a message sits in a dead-letter queue after exceeding retry limits, or when visibility timeouts expire in systems that use temporary access to messages.

Common approaches to reconsume include configurable retry attempts with backoff, exponential delays, and circuit-breaker patterns. To reduce the risks of duplicates, developers implement idempotent processing, assign unique identifiers to items, and maintain deduplication state. Some systems offer explicit dead-letter queues or separate retry topics to isolate problematic messages from normal processing.

Impact and considerations: Reconsume can affect latency and throughput; it can also complicate ordering guarantees. Architectural choices, such as at-least-once versus exactly-once delivery, influence how aggressively reconsume is applied and how duplicates are handled.