fix: moves cache for releases to API. fixes #2681 (#2686)

internal/cache/expire.go

@@ -0,0 +1,46 @@
+package cache
+
+import (
+	"time"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type Cache[T any] struct {
+	f         func() (T, error)
+	Timestamp time.Time
+	Duration  time.Duration
+	Data      T
+}
+
+func New[T any](f func() (T, error), duration time.Duration) *Cache[T] {
+	return &Cache[T]{
+		f:        f,
+		Duration: duration,
+	}
+}
+
+func (c *Cache[T]) GetWithHit() (T, error, bool) {
+	hit := true
+	if c.Timestamp.IsZero() || time.Since(c.Timestamp) > c.Duration {
+		hit = false
+
+		var err error
+		c.Data, err = c.f()
+		if err != nil {
+			return c.Data, err, hit
+		}
+		c.Timestamp = time.Now()
+	}
+	if hit {
+		log.Debugf("Cache hit for %T", c.Data)
+	} else {
+		log.Debugf("Cache miss for %T", c.Data)
+	}
+	return c.Data, nil, hit
+}
+
+func (c *Cache[T]) Get() (T, error) {
+	data, err, _ := c.GetWithHit()
+	return data, err
+}

internal/web/releases.go

@@ -3,13 +3,22 @@ package web
 import (
 	"encoding/json"
 	"net/http"
+	"time"
 
+	"github.com/amir20/dozzle/internal/cache"
 	"github.com/amir20/dozzle/internal/releases"
 	log "github.com/sirupsen/logrus"
 )
 
+var cachedReleases *cache.Cache[[]releases.Release]
+
 func (h *handler) releases(w http.ResponseWriter, r *http.Request) {
-	releases, err := releases.Fetch(h.config.Version)
+	if cachedReleases == nil {
+		cachedReleases = cache.New(func() ([]releases.Release, error) {
+			return releases.Fetch(h.config.Version)
+		}, time.Hour)
+	}
+	releases, err, hit := cachedReleases.GetWithHit()
 
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
@@ -17,8 +26,10 @@ func (h *handler) releases(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.Header().Set("Cache-Control", "max-age=3600")
 	w.Header().Set("Content-Type", "application/json")
+	if hit {
+		w.Header().Set("X-Cache", "HIT")
+	}
 
 	if err := json.NewEncoder(w).Encode(releases); err != nil {
 		log.Errorf("json encoding error while streaming %v", err.Error())