The Workflow That Sent It Twice: Reconciling Side Effects After a Retry in n8n

说明与用途

在 n8n 中，超时导致重复发送通知。解决方案是生成稳定的对账键，写入待处理账本，重试前检查账本和提供商，并使用幂等键确保单次交付。

问题

A retry timeout caused a provider to accept a second identical notification, sending the same message twice to a customer.

结果

The workflow now guarantees a single notification per business event by reconciling side effects before retrying, preventing duplicate sends caused by provider timeouts.

工作流

• Read row from sheet
• Build message
• Generate stable reconciliation key
• Write pending ledger entry
• Send notification with idempotency key
• If timeout, retry: check ledger for confirmed key
• If not confirmed, query provider by key
• If provider has record, mark ledger confirmed and skip send
• If provider has no record, send notification and record provider ID in ledger
• Assert provider count equals one after send or skip

证据

The workflow reads a row, builds a message, and calls the provider's send endpoint. The provider accepts the message, queues it, and then the connection stalls before the response comes back.

来源

A timeout lives in the gap between accepted and confirmed. Treating a timeout as failure is the mistake.

来源

Derive one stable key from the business event, not from the attempt.

来源