Serve deb virtual indexes by hash and bound cached suites

internal/virtual/engine.go

@@ -51,11 +51,14 @@ func (r *DebRepo) files() map[string][]byte { return r.Files }
 // holding the previous index can still fetch the files it references.
 type repoGen struct {
 	cur, prev mergedRepo
-	at        time.Time
+	at, used  time.Time
 }
 
 const rpmMergeTTL = 60 * time.Second
 
+// maxDebSuites bounds the client-chosen suites cached per deb virtual.
+const maxDebSuites = 32
+
 func NewEngine(db *database.DB, proxyEngine *proxy.Engine) *Engine {
 	e := &Engine{db: db, proxyEngine: proxyEngine, getRemote: db.GetRemote, mergeTTL: rpmMergeTTL}
 	e.rpmMember = e.fetchRPMMember
@@ -276,6 +279,7 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 	e.mu.Lock()
 	g := e.gens[key]
 	if g != nil && time.Since(g.at) < e.mergeTTL {
+		g.used = time.Now()
 		e.mu.Unlock()
 		return g.cur, nil
 	}
@@ -294,12 +298,12 @@ func (e *Engine) merged(ctx context.Context, key string, merge func(context.Cont
 		g := e.gens[key]
 		switch {
 		case g == nil:
-			e.gens[key] = &repoGen{cur: repo, at: time.Now()}
+			e.gens[key] = &repoGen{cur: repo, at: time.Now(), used: time.Now()}
 		case string(g.cur.index()) == string(repo.index()):
-			g.at = time.Now()
+			g.at, g.used = time.Now(), time.Now()
 			repo = g.cur
 		default:
-			g.prev, g.cur, g.at = g.cur, repo, time.Now()
+			g.prev, g.cur, g.at, g.used = g.cur, repo, time.Now(), time.Now()
 		}
 		return repo, nil
 	})
@@ -368,6 +372,7 @@ func (e *Engine) fetchDeb(ctx context.Context, virt models.Virtual, reqPath stri
 	if err != nil {
 		return nil, "", err
 	}
+	e.evictLRU("deb\x00"+virt.Name+"\x00", maxDebSuites)
 	if name == "Release" {
 		return repo.index(), "text/plain", nil
 	}
@@ -408,6 +413,22 @@ func (e *Engine) fetchDebMember(ctx context.Context, name, base string) (*DebMem
 	return m, nil
 }
 
+// evictLRU drops the least recently used merges under prefix beyond keep.
+func (e *Engine) evictLRU(prefix string, keep int) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	var keys []string
+	for k := range e.gens {
+		if strings.HasPrefix(k, prefix) {
+			keys = append(keys, k)
+		}
+	}
+	slices.SortFunc(keys, func(a, b string) int { return e.gens[b].used.Compare(e.gens[a].used) })
+	for _, k := range keys[min(len(keys), keep):] {
+		delete(e.gens, k)
+	}
+}
+
 func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
@@ -420,6 +441,7 @@ func (e *Engine) cachedFile(key, path string) ([]byte, bool) {
 			continue
 		}
 		if body, ok := r.files()[path]; ok {
+			g.used = time.Now()
 			return body, true
 		}
 	}