---
title: Observability
description: Add logging, metrics, and tracing to your self-hosted c15t backend.
---
The c15t backend supports structured logging and opt-in OpenTelemetry integration for production observability.

## OpenTelemetry

Telemetry is disabled by default. To enable it, pass your own tracer and meter instances:

```ts title="c15t.ts"
import { c15tInstance } from '@c15t/backend';
import { trace, metrics } from '@opentelemetry/api';

export const c15t = c15tInstance({
  // ...
  telemetry: {
    enabled: true,
    tracer: trace.getTracer('consent-api'),
    meter: metrics.getMeter('consent-api'),
    defaultAttributes: {
      'service.name': 'consent-api',
      environment: 'production',
    },
  },
});
```

> ℹ️ **Info:**
> You need to set up your own OpenTelemetry SDK and exporter (e.g. Jaeger, Datadog, Grafana). The c15t backend creates spans and metrics using the instances you provide.

## Metrics

When telemetry is enabled, the following metrics are recorded:

### Business Metrics

| Metric            | Type    | Description                                    |
| ----------------- | ------- | ---------------------------------------------- |
| `consentCreated`  | Counter | Consent record created (by type, jurisdiction) |
| `consentAccepted` | Counter | Consent accepted (by type)                     |
| `consentRejected` | Counter | Consent rejected (by type)                     |
| `subjectCreated`  | Counter | New subject created                            |
| `subjectLinked`   | Counter | Subject linked to external ID                  |
| `initCount`       | Counter | `/init` endpoint called                        |

### HTTP Metrics

| Metric                | Type      | Description                                 |
| --------------------- | --------- | ------------------------------------------- |
| `httpRequestDuration` | Histogram | Request duration (by method, route, status) |
| `httpRequestCount`    | Counter   | Total requests                              |
| `httpErrorCount`      | Counter   | Error responses                             |

### Database Metrics

| Metric            | Type      | Description                           |
| ----------------- | --------- | ------------------------------------- |
| `dbQueryDuration` | Histogram | Query duration (by operation, entity) |
| `dbQueryCount`    | Counter   | Total queries                         |
| `dbErrorCount`    | Counter   | Query errors                          |

### Cache Metrics

| Metric         | Type      | Description             |
| -------------- | --------- | ----------------------- |
| `cacheHit`     | Counter   | Cache hits (by layer)   |
| `cacheMiss`    | Counter   | Cache misses (by layer) |
| `cacheLatency` | Histogram | Cache operation latency |

## Tracing

Every request creates a span with:

* HTTP method and route
* Response status code
* Tenant ID (if multi-tenant)
* API key authentication status
* Geo-location resolution

Child spans are created for database queries and cache operations.

## Logging

Configure the log level:

```ts
c15tInstance({
  // ...
  logger: {
    level: 'info', // debug, info, warn, error
  },
});
```

Logs are structured (JSON-compatible) and include trace context when telemetry is enabled, making it easy to correlate logs with traces.