Cache metrics collection and reporting system.

This module tracks comprehensive cache performance metrics across all cache layers, providing insights into hit ratios, response times, memory usage, and operational efficiency.

Metrics Collected

Hit/Miss Metrics

• Cache hits per layer (L1, L2, L3)
• Cache misses per layer
• Overall hit ratio
• Hit ratio trends over time

Performance Metrics

• Average response time per operation
• P95/P99 response times
• Throughput (operations per second)
• Concurrent operation counts

Resource Metrics

• Memory usage per layer
• Storage usage (L3)
• Network usage (L2)
• CPU usage for cache operations

Operational Metrics

• Cache warming statistics
• Eviction counts and reasons
• Error rates and types
• Cleanup operation metrics

Usage Examples

# Record cache operations
Vaultx.Cache.Metrics.record_hit(:l1, "secret/myapp/config")
Vaultx.Cache.Metrics.record_miss("secret/myapp/config")

# Get comprehensive statistics
{:ok, stats} = Vaultx.Cache.Metrics.get_stats()

# Get specific layer statistics
{:ok, l1_stats} = Vaultx.Cache.Metrics.get_layer_stats(:l1)

Integration with Telemetry

All metrics are automatically emitted as telemetry events for integration with monitoring systems like Prometheus, StatsD, or custom dashboards.

# Telemetry events emitted:
[:vaultx, :cache, :hit]
[:vaultx, :cache, :miss]
[:vaultx, :cache, :operation]
[:vaultx, :cache, :eviction]
[:vaultx, :cache, :cleanup]