customerio-observability

# Customer.io Observability ## Overview Implement comprehensive observability for Customer.io integrations: Prometheus metrics (latency, error rates, delivery funnel), structured JSON logging with PII redaction, OpenTelemetry tracing, and Grafana dashboard definitions. ## Prerequisites - Customer.io integration deployed - Prometheus + Grafana (or compatible metrics stack) - Structured logging system (pino recommended) ## Key Metrics to Track | Metric | Type | Description | Alert Threshold | |--------|------|-------------|----------------| | `cio_api_duration_ms` | Histogram | API call latency | p99 > 5000ms | | `cio_api_requests_total` | Counter | Total API requests by operation | N/A (rate) | | `cio_api_errors_total` | Counter | API errors by status code | > 1% error rate | | `cio_email_sent_total` | Counter | Transactional + campaign emails | N/A | | `cio_email_bounced_total` | Counter | Bounce count | > 5% of sends | | `cio_email_complained_total` | Counter | Spam complaints | > 0.1% of sends | | `cio_webhook_received_total` | Counter | Webhook events by metric type | N/A | | `cio_queue_depth` | Gauge | Pending items in event queue | > 10K | ## Instructions ### Step 1: Prometheus Metrics ```typescript // lib/customerio-metrics.ts import { Counter, Histogram, Gauge, Registry } from "prom-client"; const registry = new Registry(); export const cioMetrics = { apiDuration: new Histogram({ name: "cio_api_duration_ms", help: "Customer.io API call duration in ...