How to Implement Request ID Tracing

What this problem means

When a user reports an error, you need to find the logs for that request. Without a request ID, you're searching through millions of log lines. A request ID is a unique identifier per request—you generate it at the edge, pass it through all services, and include it in every log.

Why this matters

- Debugging: Find all logs for a single request in seconds.

- Distributed tracing: Follow a request across services and async jobs.

- Support: "What's your request ID?" makes support tickets much faster.

Real-world example

A startup had no request IDs. When a user reported a payment failure, they had to search logs by timestamp and user ID—and hope the request was in that time window. With request IDs, they could search for "request_id: abc123" and get all logs for that request in seconds.

How to fix it

1. Generate at edge: When a request arrives, generate a UUID (e.g., `x-request-id`). Add to response headers.

2. Pass through: Include the request ID in all downstream calls—HTTP headers, async queues, etc.

3. Log it: Include request_id in every log entry. Use structured logging (JSON).

4. Return to client: Include request_id in error responses. Users can share it with support.

Tools and configurations

- express-request-id: Node.js middleware. Generates and adds to headers.

- Structured logging: Winston, Pino. Include request_id in every log.

- HTTP headers: `X-Request-ID` or `X-Correlation-ID`. Pass to downstream services.

- CloudWatch / Datadog: Search logs by request_id.

Common mistakes

- Not passing request_id to async jobs (they lose the trace).

- Not including in error responses (support can't ask for it).

- Inconsistent naming (request_id vs correlation_id).

Quick checklist

- [ ] Generate request_id at edge (middleware)

- [ ] Pass to all downstream services and async jobs

- [ ] Include in every log entry

- [ ] Return in error responses for support

- [ ] Use consistent header name (X-Request-ID)