# ADR-0005: Logging Framework

## Status
Accepted

## Context
The platform requires structured logging that:
- Supports multiple log levels
- Provides structured output (JSON for production)
- Allows adding contextual fields
- Performs well under load
- Integrates with observability tools

Options considered:
1. **go.uber.org/zap** - High-performance structured logging
2. **rs/zerolog** - Zero-allocation logger
3. **sirupsen/logrus** - Structured logger (maintenance mode)
4. **Standard library log** - Basic logging (insufficient)

## Decision
Use **go.uber.org/zap** (v1.26.0+) as the logging framework.

**Rationale:**
- Industry standard for high-performance Go applications
- Excellent structured logging with field support
- Very low overhead (designed for high-throughput systems)
- JSON output for production, human-readable for development
- Strong ecosystem integration
- Actively maintained by Uber

## Consequences

### Positive
- High performance (low latency, high throughput)
- Rich structured logging with fields
- Easy integration with observability tools
- Configurable output formats (JSON/console)

### Negative
- Slightly more verbose API than standard library
- Requires wrapping for common use cases (we'll abstract via interface)

### Implementation Notes
- Install: `go get go.uber.org/zap@v1.26.0`
- Create `pkg/logger/logger.go` interface to abstract zap
- Implement `internal/logger/zap_logger.go` as concrete implementation
- Use JSON encoder for production, console encoder for development
- Support request-scoped fields via context
- Export global logger via `pkg/logger` package