feat(exporter): add prometheus exporter for cache, database & webserver stats

internal/exporter/collector.go

@@ -0,0 +1,46 @@
+package exporter
+
+import (
+	"git.ar21.de/yolokube/country-geo-locations/internal/cache"
+	"git.ar21.de/yolokube/country-geo-locations/internal/cmd"
+	"git.ar21.de/yolokube/country-geo-locations/internal/database"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type Collector struct {
+	config  *cmd.AppSettings
+	cache   *cache.Cache
+	db      *database.Database
+	metrics *Metrics
+	queue   *RequestDataQueue
+}
+
+func NewCollector(
+	config *cmd.AppSettings,
+	cache *cache.Cache,
+	db *database.Database,
+	queue *RequestDataQueue,
+) *Collector {
+	return &Collector{
+		config:  config,
+		cache:   cache,
+		db:      db,
+		metrics: NewMetrics(),
+		queue:   queue,
+	}
+}
+
+func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- c.metrics.metricCacheTTL
+	ch <- c.metrics.metricCurrentlyCached
+	ch <- c.metrics.metricDatabaseTimestamp
+	ch <- c.metrics.metricDatabaseReady
+}
+
+func (c *Collector) Collect(ch chan<- prometheus.Metric) {
+	c.metrics.collectCacheTTLMetric(ch, c.config.CacheTTL.Seconds())
+	c.metrics.collectCurrentlyCachedMetric(ch, float64(c.cache.Count()))
+	c.metrics.collectDatabaseTimestampMetric(ch, c.db)
+	c.metrics.collectDatabaseReadyMetric(ch, c.db.IsReady())
+	c.metrics.collectReqeustDataMetrics(ch, c.queue)
+}