From 1d98e4827ee1f741b43d0d434b1715d2a836ce1f Mon Sep 17 00:00:00 2001
From: jkoberg <jkoberg@owncloud.com>
Date: Sat, 5 Mar 2022 12:57:57 +0100
Subject: [PATCH] add caching

Signed-off-by: jkoberg <jkoberg@owncloud.com>
---
 settings/pkg/store/metadata/cache.go | 124 +++++++++++++++++++++++++++
 settings/pkg/store/metadata/store.go |   7 +-
 2 files changed, 130 insertions(+), 1 deletion(-)
 create mode 100644 settings/pkg/store/metadata/cache.go

diff --git a/settings/pkg/store/metadata/cache.go b/settings/pkg/store/metadata/cache.go
new file mode 100644
index 0000000000..f2e80d8ca2
--- /dev/null
+++ b/settings/pkg/store/metadata/cache.go
@@ -0,0 +1,124 @@
+package store
+
+import (
+	"context"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/ReneKroon/ttlcache/v2"
+)
+
+var (
+	cachettl = 0
+	// these need to be global instances for now as the `Service` (and therefore the `Store`) are instantiated twice (for grpc and http)
+	// therefore caches need to cover both instances
+	dircache   = initCache(cachettl)
+	filescache = initCache(cachettl)
+)
+
+// CachedMDC is cache for the metadataclient
+type CachedMDC struct {
+	next MetadataClient
+
+	files *ttlcache.Cache
+	dirs  *ttlcache.Cache
+}
+
+// SimpleDownload caches the answer from SimpleDownload or returns the cached one
+func (c *CachedMDC) SimpleDownload(ctx context.Context, id string) ([]byte, error) {
+	if b, err := c.files.Get(id); err == nil {
+		return b.([]byte), nil
+	}
+	b, err := c.next.SimpleDownload(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	c.files.Set(id, b)
+	return b, nil
+}
+
+// SimpleUpload caches the answer from SimpleUpload and invalidates the cache
+func (c *CachedMDC) SimpleUpload(ctx context.Context, id string, content []byte) error {
+	b, err := c.files.Get(id)
+	if err == nil && string(b.([]byte)) == string(content) {
+		// no need to bug mdc
+		return nil
+	}
+
+	err = c.next.SimpleUpload(ctx, id, content)
+	if err != nil {
+		return err
+	}
+
+	// invalidate caches
+	err = c.dirs.Remove(path.Dir(id))
+	err = c.files.Set(id, content)
+	return nil
+}
+
+// Delete invalidates the cache when operation was successful
+func (c *CachedMDC) Delete(ctx context.Context, id string) error {
+	err := c.next.Delete(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	// invalidate caches
+	_ = removePrefix(c.files, id)
+	_ = removePrefix(c.dirs, id)
+	return nil
+}
+
+// ReadDir caches the response from ReadDir or returnes the cached one
+func (c *CachedMDC) ReadDir(ctx context.Context, id string) ([]string, error) {
+	i, err := c.dirs.Get(id)
+	if err == nil {
+		return i.([]string), nil
+	}
+
+	s, err := c.next.ReadDir(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	return s, c.dirs.Set(id, s)
+}
+
+// MakeDirIfNotExist invalidates the cache
+func (c *CachedMDC) MakeDirIfNotExist(ctx context.Context, id string) error {
+	err := c.next.MakeDirIfNotExist(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	// invalidate caches
+	_ = c.dirs.Remove(path.Dir(id))
+	return nil
+}
+
+// Init instantiates the caches
+func (c *CachedMDC) Init(ctx context.Context, id string) error {
+	c.dirs = dircache
+	c.files = filescache
+	return c.next.Init(ctx, id)
+}
+
+func initCache(ttlSeconds int) *ttlcache.Cache {
+	cache := ttlcache.NewCache()
+	_ = cache.SetTTL(time.Duration(ttlSeconds) * time.Second)
+	cache.SkipTTLExtensionOnHit(true)
+	return cache
+}
+
+func removePrefix(cache *ttlcache.Cache, prefix string) error {
+	for _, k := range cache.GetKeys() {
+		if strings.HasPrefix(k, prefix) {
+			if err := cache.Remove(k); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
diff --git a/settings/pkg/store/metadata/store.go b/settings/pkg/store/metadata/store.go
index 6ba5fcab2c..e0106f6ca7 100644
--- a/settings/pkg/store/metadata/store.go
+++ b/settings/pkg/store/metadata/store.go
@@ -58,8 +58,13 @@ func (s *Store) Init() {
 	s.l.Lock()
 	defer s.l.Unlock()
 
+	if s.mdc != nil {
+		return
+	}
+
 	//s.init.Do(func() {
-	if err := s.initMetadataClient(NewMetadataClient(s.cfg.Metadata)); err != nil {
+	mdc := &CachedMDC{next: NewMetadataClient(s.cfg.Metadata)}
+	if err := s.initMetadataClient(mdc); err != nil {
 		s.Logger.Error().Err(err).Msg("error initializing metadata client")
 	}
 	//})