Event-Driven Pub/Sub Bus for n8n: Webhooks, HTTP & Slack

Event-Driven Pub/Sub Bus for n8n — Webhooks, HTTP Subscribers, and Slack Alerts

This n8n workflow acts as an event-driven Pub/Sub bus: it receives event envelopes via HTTP webhook or Execute Workflow, validates and stores them in an external event store, then fans out deliveries to subscriber HTTP endpoints with exponential backoff retries, a dead-letter queue, and Slack notifications on failures.

What this workflow does

• Receives events either from an HTTP POST webhook or from another workflow using Execute Workflow.
• Validates & normalizes the event envelope fields: eventType, eventId, source, timestamp, payload. Invalid requests are rejected with a 400 response.
• Appends valid events to an external event store via HTTP, then returns a 202 Accepted webhook response.
• Routes and fans out deliveries by eventType to subscriber services via HTTP (including an Order Service, Notification Service, and an Analytics Service catch-all for unknown types).
• Retries on failure using exponential backoff up to a configurable maximum number of attempts.
• Dead-letter handling: once retries are exhausted, it writes the failed delivery to an external dead-letter queue over HTTP and posts an alert to a Slack channel.
• Acknowledges success by notifying the event store over HTTP when delivery completes successfully.

Use cases

• Decouple services by publishing order and notification events from n8n while subscribers receive HTTP callbacks.
• Centralize event ingestion from webhooks and route unknown events to Analytics without breaking the pipeline.
• Improve reliability for SaaS integrations using retries, dead-letter queue escalation, and Slack failure alerts.

Technical details

• Nodes/logic: if, set, code, wait, merge, slack.
• Integrations (HTTP): event store append URL, event store ack URL, subscriber HTTP endpoints, and external dead-letter queue URL.
• Slack: failure alerts to a configured channel when deliveries land in the dead-letter queue.

To set it up, provide reachable HTTP endpoints for the event store append/ack and dead-letter queue, then replace the placeholders in the workflow configuration.