3 files changed, 58 insertions(+), 12 deletions(-)

M database/db.go
M database/fs.go
M server.go

@@ 4,25 4,76 @@ import (
 	"git.sr.ht/~emersion/drmdb/drmtree"
 )
 
+const cacheSize = 1000
+
+type cacheEntry struct {
+	key  string
+	node *drmtree.Node
+}
+
 type DB struct {
+	cache   []cacheEntry   // ring buffer
+	indexes map[string]int // key → cache index
+	cur     int
 }
 
 func Open() (*DB, error) {
-	return &DB{}, initDB()
+	if err := initDB(); err != nil {
+		return nil, err
+	}
+	return &DB{
+		cache:   make([]cacheEntry, cacheSize),
+		indexes: make(map[string]int, cacheSize),
+	}, nil
+}
+
+func (db *DB) storeCache(k string, n *drmtree.Node) {
+	prev := db.cache[db.cur]
+	delete(db.indexes, prev.key)
+	db.cache[db.cur] = cacheEntry{key: k, node: n}
+	db.indexes[k] = db.cur
+	db.cur = (db.cur + 1) % len(db.cache)
+}
+
+func (db *DB) loadCache(k string) *drmtree.Node {
+	i, ok := db.indexes[k]
+	if !ok {
+		return nil
+	}
+	return db.cache[i].node
 }
 
 func (db *DB) Store(n *drmtree.Node) (string, error) {
-	return store(n)
+	k, err := store(n)
+	if err == nil {
+		db.storeCache(k, n)
+	}
+	return k, err
 }
 
 func (db *DB) Load(k string) (*drmtree.Node, error) {
-	return load(k)
+	if n := db.loadCache(k); n != nil {
+		return n, nil
+	}
+	n, err := load(k)
+	if err == nil {
+		db.storeCache(k, n)
+	}
+	return n, err
 }
 
 func (db *DB) Walk(fn func(k string, n *drmtree.Node) error) error {
-	return walk(fn)
+	return walk(func(k string) error {
+		n, err := db.Load(k)
+		if err != nil {
+			return err
+		}
+		return fn(k, n)
+	})
 }
 
 func (db *DB) Close() error {
+	db.cache = nil
+	db.indexes = nil
 	return nil
 }

@@ 99,7 99,7 @@ func load(k string) (*drmtree.Node, error) {
 	return &n, f.Close()
 }
 
-func walk(fn func(k string, n *drmtree.Node) error) error {
+func walk(fn func(k string) error) error {
 	files, err := ioutil.ReadDir(Dir)
 	if err != nil {
 		return err


@@ 111,12 111,7 @@ func walk(fn func(k string, n *drmtree.Node) error) error {
 		}
 		k := strings.TrimSuffix(fi.Name(), ".json")
 
-		n, err := load(k)
-		if err != nil {
-			return err
-		}
-
-		if err := fn(k, n); err == ErrStop {
+		if err := fn(k); err == ErrStop {
 			return nil
 		} else if err != nil {
 			return err

@@ 76,7 76,7 @@ func New() *echo.Echo {
 
 	e.GET("/", func(c echo.Context) error {
 		data := struct {
-			Host string
+			Host         string
 			NumSnapshots int
 			NumDevices   int
 			NumDrivers   int