fix(core): change name of config flag for cache (#9274)

Author: Harshil Goel

dgraph/cmd/alpha/run.go

@@ -145,8 +145,12 @@ they form a Raft group and provide synchronous replication.
 		Flag("percentage",
 			"Cache percentages summing up to 100 for various caches (FORMAT: PostingListCache,"+
 				"PstoreBlockCache,PstoreIndexCache)").
-		Flag("keep-updates",
-			"Should carry updates in cache or not (bool)").
+		Flag("delete-on-updates",
+			"When set as true, we would delete the key from the cache once it's updated. If it's not "+
+				"we would update the value inside the cache. If the cache gets too full, it starts"+
+				" to get slow. So if your usecase has a lot of heavy mutations, this should be set"+
+				" as true. If you are modifying same data again and again, this should be set as"+
+				" false").
 		String())
 
 	flag.String("raft", worker.RaftDefaults, z.NewSuperFlagHelp(worker.RaftDefaults).
@@ -635,7 +639,7 @@ func run() {
 	x.AssertTruef(totalCache >= 0, "ERROR: Cache size must be non-negative")
 
 	cachePercentage := cache.GetString("percentage")
-	keepUpdates := cache.GetBool("keep-updates")
+	deleteOnUpdates := cache.GetBool("delete-on-updates")
 	cachePercent, err := x.GetCachePercentages(cachePercentage, 3)
 	x.Check(err)
 	postingListCacheSize := (cachePercent[0] * (totalCache << 20)) / 100
@@ -658,7 +662,7 @@ func run() {
 		WALDir:          Alpha.Conf.GetString("wal"),
 		CacheMb:         totalCache,
 		CachePercentage: cachePercentage,
-		KeepUpdates:     keepUpdates,
+		DeleteOnUpdates: deleteOnUpdates,
 
 		MutationsMode:      worker.AllowMutations,
 		AuthToken:          security.GetString("token"),
@@ -786,7 +790,7 @@ func run() {
 	// Posting will initialize index which requires schema. Hence, initialize
 	// schema before calling posting.Init().
 	schema.Init(worker.State.Pstore)
-	posting.Init(worker.State.Pstore, postingListCacheSize, keepUpdates)
+	posting.Init(worker.State.Pstore, postingListCacheSize, deleteOnUpdates)
 	defer posting.Cleanup()
 	worker.Init(worker.State.Pstore)
 

posting/lists.go

@@ -41,12 +41,12 @@ var (
 )
 
 // Init initializes the posting lists package, the in memory and dirty list hash.
-func Init(ps *badger.DB, cacheSize int64, keepUpdates bool) {
+func Init(ps *badger.DB, cacheSize int64, deleteOnUpdates bool) {
 	pstore = ps
 	closer = z.NewCloser(1)
 	go x.MonitorMemoryMetrics(closer)
 
-	memoryLayer = initMemoryLayer(cacheSize, keepUpdates)
+	memoryLayer = initMemoryLayer(cacheSize, deleteOnUpdates)
 }
 
 func UpdateMaxCost(maxCost int64) {

posting/mvcc.go

@@ -63,10 +63,8 @@ type incrRollupi struct {
 }
 
 type CachePL struct {
-	count      int
 	list       *List
 	lastUpdate uint64
-	lastRead   time.Time
 }
 
 var (
@@ -401,8 +399,8 @@ func (c *Cache) clear() {
 }
 
 type MemoryLayer struct {
-	keepUpdates bool
-	cache       *Cache
+	deleteOnUpdates bool
+	cache           *Cache
 
 	numDisksRead int
 }
@@ -414,9 +412,9 @@ func (ml *MemoryLayer) del(key []byte) {
 	ml.cache.del(key)
 }
 
-func initMemoryLayer(cacheSize int64, keepUpdates bool) *MemoryLayer {
+func initMemoryLayer(cacheSize int64, deleteOnUpdates bool) *MemoryLayer {
 	ml := &MemoryLayer{}
-	ml.keepUpdates = keepUpdates
+	ml.deleteOnUpdates = deleteOnUpdates
 	if cacheSize > 0 {
 		cache, err := ristretto.NewCache[[]byte, *CachePL](&ristretto.Config[[]byte, *CachePL]{
 			// Use 5% of cache memory for storing counters.
@@ -449,9 +447,7 @@ func initMemoryLayer(cacheSize int64, keepUpdates bool) *MemoryLayer {
 
 func NewCachePL() *CachePL {
 	return &CachePL{
-		count:      0,
-		list:       nil,
-		lastUpdate: 0,
+		list: nil,
 	}
 }
 
@@ -472,7 +468,7 @@ func (ml *MemoryLayer) updateItemInCache(key string, delta []byte, startTs, comm
 		return
 	}
 
-	if !ml.keepUpdates {
+	if ml.deleteOnUpdates {
 		// TODO We should mark the key as deleted instead of directly deleting from the cache.
 		ml.del([]byte(key))
 		return
@@ -484,9 +480,8 @@ func (ml *MemoryLayer) updateItemInCache(key string, delta []byte, startTs, comm
 	}
 
 	val.lastUpdate = commitTs
-	val.count -= 1
 
-	if val.list != nil && ml.keepUpdates {
+	if val.list != nil {
 		p := new(pb.PostingList)
 		x.Check(proto.Unmarshal(delta, p))
 
@@ -640,16 +635,12 @@ func (c *CachePL) Set(l *List, readTs uint64) {
 func (ml *MemoryLayer) readFromCache(key []byte, readTs uint64) *List {
 	cacheItem, ok := ml.cache.get(key)
 
-	if ok {
-		cacheItem.count += 1
-		cacheItem.lastRead = time.Now()
-		if cacheItem.list != nil && cacheItem.list.minTs <= readTs {
-			cacheItem.list.RLock()
-			lCopy := copyList(cacheItem.list)
-			cacheItem.list.RUnlock()
-			checkForRollup(key, lCopy)
-			return lCopy
-		}
+	if ok && cacheItem.list != nil && cacheItem.list.minTs <= readTs {
+		cacheItem.list.RLock()
+		lCopy := copyList(cacheItem.list)
+		cacheItem.list.RUnlock()
+		checkForRollup(key, lCopy)
+		return lCopy
 	}
 	return nil
 }
@@ -679,7 +670,6 @@ func (ml *MemoryLayer) saveInCache(key []byte, l *List) {
 	l.RLock()
 	defer l.RUnlock()
 	cacheItem := NewCachePL()
-	cacheItem.count = 1
 	cacheItem.list = copyList(l)
 	cacheItem.lastUpdate = l.maxTs
 	ml.cache.set(key, cacheItem)

worker/config.go

@@ -63,11 +63,11 @@ type Options struct {
 	CachePercentage string
 	// CacheMb is the total memory allocated between all the caches.
 	CacheMb int64
-	// KeepUpdates is the parameter that allows the user to set if the cache should keep the items that were
+	// DeleteOnUpdates is the parameter that allows the user to set if the cache should keep the items that were
 	// just mutated. Keeping these items are good when there is a mixed workload where you are updating the
 	// same element multiple times. However, for a heavy mutation workload, not keeping these items would be better
 	// , as keeping these elements bloats the cache making it slow.
-	KeepUpdates bool
+	DeleteOnUpdates bool
 
 	Audit *x.LoggerConf
 

worker/server_state.go

@@ -52,7 +52,7 @@ const (
 	ZeroLimitsDefaults = `uid-lease=0; refill-interval=30s; disable-admin-http=false;`
 	GraphQLDefaults    = `introspection=true; debug=false; extensions=true; poll-interval=1s; ` +
 		`lambda-url=;`
-	CacheDefaults        = `size-mb=1024; percentage=40,40,20; keep-updates=false`
+	CacheDefaults        = `size-mb=1024; percentage=40,40,20; delete-on-updates=true`
 	FeatureFlagsDefaults = `normalize-compatibility-mode=`
 )