Trace simulated card charges with OpenTelemetry and Jaeger

Description

Quick overview
This workflow simulates a card charge so you can send n8n's OpenTelemetry spans to a local Jaeger collector and compare a successful run with a deliberate failure. It needs no LLM credential. It is Exercise 3 from the n8n Production AI Playbook on Audit & Trace.

How it works
Receives a POST webhook request with a requestId and amount.
Validate Amount, an If node, sends invalid amounts to Reject Request, a Stop and Error node.
Normalize Request, an Edit Fields node, converts the amount to cents.
Charge Card, an If node, routes requests with trigger_failure to Decline Charge, a Stop and Error node that fails with card_declined.
Capture Charge records the successful charge, and Respond returns it.

Setup
Run Jaeger locally (image jaegertracing/jaeger:2.20.0 with ports 16686 and 4318) and expose port 4318 with cloudflared tunnel --url http://localhost:4318.
As an instance owner or admin, open Settings > OpenTelemetry, enter the tunnel URL as the OTLP endpoint, set the sample rate to 1, turn off Track published workflows only, and enable tracing.
Select Execute workflow and POST {"requestId":"REQ-3001","amount":49.99}, then {"requestId":"REQ-3002","amount":49.99,"trigger_failure":true}.
In Jaeger, search the tag n8n.execution.id with each execution ID and inspect the spans.

Requirements
n8n Cloud or a self-hosted n8n instance, with owner or admin access to Settings > OpenTelemetry
Docker Desktop to run Jaeger locally
cloudflared to give n8n Cloud an HTTPS address for the local collector

Customization
Send spans to your existing OpenTelemetry collector instead of a local Jaeger instance.

Additional info
OpenTelemetry tracing in n8n is in Preview. No payment provider is called.