cloudflare/pint
Publicmirrored from https://github.com/cloudflare/pintAvailable
internal/promapi/cache.go
157lines · modecode
| 1 | package promapi |
| 2 | |
| 3 | import ( |
| 4 | "sync" |
| 5 | "time" |
| 6 | |
| 7 | "github.com/prometheus/client_golang/prometheus" |
| 8 | ) |
| 9 | |
| 10 | type cacheEntry struct { |
| 11 | data any |
| 12 | expiresAt time.Time |
| 13 | lastGet time.Time |
| 14 | } |
| 15 | |
| 16 | type endpointStats struct { |
| 17 | hits int |
| 18 | misses int |
| 19 | } |
| 20 | |
| 21 | func (e *endpointStats) hit() { e.hits++ } |
| 22 | func (e *endpointStats) miss() { e.misses++ } |
| 23 | |
| 24 | func newQueryCache(maxStale time.Duration) *queryCache { |
| 25 | // nolint: exhaustruct |
| 26 | return &queryCache{ |
| 27 | entries: map[uint64]*cacheEntry{}, |
| 28 | stats: map[string]*endpointStats{}, |
| 29 | maxStale: maxStale, |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | type queryCache struct { |
| 34 | entries map[uint64]*cacheEntry |
| 35 | stats map[string]*endpointStats |
| 36 | maxStale time.Duration |
| 37 | evictions int |
| 38 | mu sync.Mutex |
| 39 | } |
| 40 | |
| 41 | func (c *queryCache) endpointStats(endpoint string) *endpointStats { |
| 42 | e, ok := c.stats[endpoint] |
| 43 | if ok { |
| 44 | return e |
| 45 | } |
| 46 | |
| 47 | e = &endpointStats{hits: 0, misses: 0} |
| 48 | c.stats[endpoint] = e |
| 49 | return e |
| 50 | } |
| 51 | |
| 52 | func (c *queryCache) get(key uint64, endpoint string) (v any, ok bool) { |
| 53 | c.mu.Lock() |
| 54 | defer c.mu.Unlock() |
| 55 | |
| 56 | var ce *cacheEntry |
| 57 | ce, ok = c.entries[key] |
| 58 | if !ok { |
| 59 | c.endpointStats(endpoint).miss() |
| 60 | return v, ok |
| 61 | } |
| 62 | |
| 63 | ce.lastGet = time.Now() |
| 64 | c.endpointStats(endpoint).hit() |
| 65 | |
| 66 | return ce.data, true |
| 67 | } |
| 68 | |
| 69 | // Cache results if it was requested at least twice EVER - which means it's either |
| 70 | // popular and requested multiple times within a loop OR this cache key survives between loops. |
| 71 | func (c *queryCache) set(key uint64, val any, ttl time.Duration) { |
| 72 | c.mu.Lock() |
| 73 | defer c.mu.Unlock() |
| 74 | |
| 75 | c.entries[key] = &cacheEntry{ |
| 76 | data: val, |
| 77 | lastGet: time.Now(), |
| 78 | expiresAt: time.Time{}, |
| 79 | } |
| 80 | if ttl > 0 { |
| 81 | c.entries[key].expiresAt = time.Now().Add(ttl) |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | func (c *queryCache) gc() { |
| 86 | c.mu.Lock() |
| 87 | defer c.mu.Unlock() |
| 88 | |
| 89 | entries := map[uint64]*cacheEntry{} |
| 90 | |
| 91 | now := time.Now() |
| 92 | for key, ce := range c.entries { |
| 93 | if (!ce.expiresAt.IsZero() && ce.expiresAt.Before(now)) || now.Sub(ce.lastGet) >= c.maxStale { |
| 94 | c.evictions++ |
| 95 | continue |
| 96 | } |
| 97 | entries[key] = ce |
| 98 | } |
| 99 | c.entries = entries |
| 100 | } |
| 101 | |
| 102 | type cacheCollector struct { |
| 103 | cache *queryCache |
| 104 | entries *prometheus.Desc |
| 105 | hits *prometheus.Desc |
| 106 | misses *prometheus.Desc |
| 107 | evictions *prometheus.Desc |
| 108 | } |
| 109 | |
| 110 | func newCacheCollector(cache *queryCache, name string) *cacheCollector { |
| 111 | return &cacheCollector{ |
| 112 | cache: cache, |
| 113 | entries: prometheus.NewDesc( |
| 114 | "pint_prometheus_cache_size", |
| 115 | "Total number of entries currently stored in Prometheus query cache", |
| 116 | nil, |
| 117 | prometheus.Labels{"name": name}, |
| 118 | ), |
| 119 | hits: prometheus.NewDesc( |
| 120 | "pint_prometheus_cache_hits_total", |
| 121 | "Total number of query cache hits", |
| 122 | []string{"endpoint"}, |
| 123 | prometheus.Labels{"name": name}, |
| 124 | ), |
| 125 | misses: prometheus.NewDesc( |
| 126 | "pint_prometheus_cache_miss_total", |
| 127 | "Total number of query cache misses", |
| 128 | []string{"endpoint"}, |
| 129 | prometheus.Labels{"name": name}, |
| 130 | ), |
| 131 | evictions: prometheus.NewDesc( |
| 132 | "pint_prometheus_cache_evictions_total", |
| 133 | "Total number of times an entry was evicted from query cache due to size limit or TTL", |
| 134 | nil, |
| 135 | prometheus.Labels{"name": name}, |
| 136 | ), |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | func (c *cacheCollector) Describe(ch chan<- *prometheus.Desc) { |
| 141 | ch <- c.entries |
| 142 | ch <- c.hits |
| 143 | ch <- c.misses |
| 144 | ch <- c.evictions |
| 145 | } |
| 146 | |
| 147 | func (c *cacheCollector) Collect(ch chan<- prometheus.Metric) { |
| 148 | c.cache.mu.Lock() |
| 149 | defer c.cache.mu.Unlock() |
| 150 | ch <- prometheus.MustNewConstMetric(c.entries, prometheus.GaugeValue, float64(len(c.cache.entries))) |
| 151 | |
| 152 | for endpoint, stats := range c.cache.stats { |
| 153 | ch <- prometheus.MustNewConstMetric(c.hits, prometheus.CounterValue, float64(stats.hits), endpoint) |
| 154 | ch <- prometheus.MustNewConstMetric(c.misses, prometheus.CounterValue, float64(stats.misses), endpoint) |
| 155 | } |
| 156 | ch <- prometheus.MustNewConstMetric(c.evictions, prometheus.CounterValue, float64(c.cache.evictions)) |
| 157 | } |
| 158 | |