Fix ever existing iterator and transaction in write benchmark (dgraph…

…-io#1457)

91a80ef (Add support collecting stats (sst count, vlog count, file sizes, move key count, valid keys etc) introduced count of various types of keys in the report (log) of the benchmark write tool. For counting various keys, iterators were used in the function `reportStats()` and the keys were counted periodically. For closing the iterators `defer it.close()` was used, which never closed iterators until `reportStats()` returned. This caused the iterators to accumulate and hence resulting in excessive memory usage. 

Now, this key count is made optional by the introduction of a new option `--show-keys`, which is disabled by default. The statistics is collected in a separate function and the iterators are properly closed after each iteration cycle. Also the transaction is properly discarded after each run.

badger/cmd/write_bench.go

@@ -71,14 +71,11 @@ var (
 	compression         bool
 	showDir             bool
 	ttlDuration         string
+	showKeysCount       bool
 
-	internalKeyCount uint32
-	moveKeyCount     uint32
-	invalidKeyCount  uint32
-	validKeyCount    uint32
-	sstCount         uint32
-	vlogCount        uint32
-	files            []string
+	sstCount  uint32
+	vlogCount uint32
+	files     []string
 
 	dropAllPeriod    string
 	dropPrefixPeriod string
@@ -133,6 +130,8 @@ func init() {
 		"TTL duration in seconds for the entries, 0 means without TTL")
 	writeBenchCmd.Flags().StringVarP(&gcPeriod, "gc-every", "g", "5m", "GC Period.")
 	writeBenchCmd.Flags().Float64VarP(&gcDiscardRatio, "gc-ratio", "r", 0.5, "GC discard ratio.")
+	writeBenchCmd.Flags().BoolVar(&showKeysCount, "show-keys", false,
+		"If true, the report will include the keys statistics")
 }
 
 func writeRandom(db *badger.DB, num uint64) error {
@@ -298,6 +297,42 @@ func writeBench(cmd *cobra.Command, args []string) error {
 	return err
 }
 
+func showKeysStats(db *badger.DB) {
+	var (
+		internalKeyCount uint32
+		moveKeyCount     uint32
+		invalidKeyCount  uint32
+		validKeyCount    uint32
+	)
+
+	txn := db.NewTransaction(false)
+	defer txn.Discard()
+
+	iopt := badger.DefaultIteratorOptions
+	iopt.AllVersions = true
+	iopt.InternalAccess = true
+	it := txn.NewIterator(iopt)
+	defer it.Close()
+
+	for it.Rewind(); it.Valid(); it.Next() {
+		i := it.Item()
+		if bytes.HasPrefix(i.Key(), []byte("!badger!")) {
+			internalKeyCount++
+		}
+		if bytes.HasPrefix(i.Key(), []byte("!badger!Move")) {
+			moveKeyCount++
+		}
+		if i.IsDeletedOrExpired() {
+			invalidKeyCount++
+		} else {
+			validKeyCount++
+		}
+	}
+	fmt.Printf("Valid Keys: %d Invalid Keys: %d Move Keys:"+
+		" %d Internal Keys: %d\n", validKeyCount, invalidKeyCount,
+		moveKeyCount, internalKeyCount)
+}
+
 func reportStats(c *y.Closer, db *badger.DB) {
 	defer c.Done()
 
@@ -309,28 +344,8 @@ func reportStats(c *y.Closer, db *badger.DB) {
 		case <-c.HasBeenClosed():
 			return
 		case <-t.C:
-			txn := db.NewTransaction(false)
-			defer txn.Discard()
-
-			iopt := badger.DefaultIteratorOptions
-			iopt.AllVersions = true
-			iopt.InternalAccess = true
-
-			it := txn.NewIterator(iopt)
-			defer it.Close()
-			for it.Rewind(); it.Valid(); it.Next() {
-				i := it.Item()
-				if bytes.HasPrefix(i.Key(), []byte("!badger!")) {
-					internalKeyCount++
-				}
-				if bytes.HasPrefix(i.Key(), []byte("!badger!Move")) {
-					moveKeyCount++
-				}
-				if i.IsDeletedOrExpired() {
-					invalidKeyCount++
-				} else {
-					validKeyCount++
-				}
+			if showKeysCount {
+				showKeysStats(db)
 			}
 
 			// fetch directory contents
@@ -365,9 +380,6 @@ func reportStats(c *y.Closer, db *badger.DB) {
 			fmt.Printf("Time elapsed: %s, bytes written: %s, speed: %s/sec, "+
 				"entries written: %d, speed: %d/sec, gcSuccess: %d\n", y.FixedDuration(time.Since(startTime)),
 				humanize.Bytes(sz), humanize.Bytes(bytesRate), entries, entriesRate, gcSuccess)
-			fmt.Printf("Valid Keys Count: %d\nInvalid Keys Count: %d\nMove Keys Count: %d\n"+
-				"Internal Keys Count: %d\n", validKeyCount, invalidKeyCount, moveKeyCount,
-				internalKeyCount)
 		}
 	}
 }