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feat: collect ristretto cache metrics helper #834

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Jan 27, 2025
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67 changes: 67 additions & 0 deletions cachex/ristretto.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,67 @@
// Copyright © 2025 Ory Corp
// SPDX-License-Identifier: Apache-2.0

package cachex

import (
"github.com/dgraph-io/ristretto"
"github.com/prometheus/client_golang/prometheus"
)

// RistrettoCollector collects Ristretto cache metrics.
type RistrettoCollector[K ristretto.Key, V any] struct {
prefix string
metricsFunc func() *ristretto.Metrics
}

// NewRistrettoCollector creates a new RistrettoCollector.
//
// To use this collector, you need to register it with a Prometheus registry:
//
// func main() {
// cache, _ := ristretto.NewCache(&ristretto.Config{
// NumCounters: 1e7,
// MaxCost: 1 << 30,
// BufferItems: 64,
// })
// collector := NewRistrettoCollector("prefix_", func() *ristretto.Metrics {
// return cache.Metrics
// })
// prometheus.MustRegister(collector)
// }
func NewRistrettoCollector[K ristretto.Key, V any](prefix string, metricsFunc func() *ristretto.Metrics) *RistrettoCollector[K, V] {
return &RistrettoCollector[K, V]{
prefix: prefix,
metricsFunc: metricsFunc,
}
}

// Describe sends the super-set of all possible descriptors of metrics
// collected by this Collector.
func (c *RistrettoCollector[K, V]) Describe(ch chan<- *prometheus.Desc) {
ch <- prometheus.NewDesc(c.prefix+"ristretto_hits", "Total number of cache hits", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_misses", "Total number of cache misses", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_ratio", "Cache hit ratio", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_keys_added", "Total number of keys added to the cache", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_cost_added", "Total cost of keys added to the cache", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_keys_evicted", "Total number of keys evicted from the cache", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_cost_evicted", "Total cost of keys evicted from the cache", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_sets_dropped", "Total number of sets dropped", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_sets_rejected", "Total number of sets rejected", nil, nil)
ch <- prometheus.NewDesc(c.prefix+"ristretto_gets_kept", "Total number of gets kept", nil, nil)
}

// Collect is called by the Prometheus registry when collecting metrics.
func (c *RistrettoCollector[K, V]) Collect(ch chan<- prometheus.Metric) {
metrics := c.metricsFunc()
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_hits", "Total number of cache hits", nil, nil), prometheus.GaugeValue, float64(metrics.Hits()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_misses", "Total number of cache misses", nil, nil), prometheus.GaugeValue, float64(metrics.Misses()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_ratio", "Cache hit ratio", nil, nil), prometheus.GaugeValue, metrics.Ratio())
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_keys_added", "Total number of keys added to the cache", nil, nil), prometheus.GaugeValue, float64(metrics.KeysAdded()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_cost_added", "Total cost of keys added to the cache", nil, nil), prometheus.GaugeValue, float64(metrics.CostAdded()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_keys_evicted", "Total number of keys evicted from the cache", nil, nil), prometheus.GaugeValue, float64(metrics.KeysEvicted()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_cost_evicted", "Total cost of keys evicted from the cache", nil, nil), prometheus.GaugeValue, float64(metrics.CostEvicted()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_sets_dropped", "Total number of sets dropped", nil, nil), prometheus.GaugeValue, float64(metrics.SetsDropped()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_sets_rejected", "Total number of sets rejected", nil, nil), prometheus.GaugeValue, float64(metrics.SetsRejected()))
ch <- prometheus.MustNewConstMetric(prometheus.NewDesc(c.prefix+"ristretto_gets_kept", "Total number of gets kept", nil, nil), prometheus.GaugeValue, float64(metrics.GetsKept()))
}
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