Add EventLogging option

db.go

@@ -270,13 +270,18 @@ func Open(opt Options) (db *DB, err error) {
 		}
 	}()
 
+	elog := noEventLog
+	if opt.EventLogging {
+		elog = trace.NewEventLog("Badger", "DB")
+	}
+
 	db = &DB{
 		imm:           make([]*skl.Skiplist, 0, opt.NumMemtables),
 		flushChan:     make(chan flushTask, opt.NumMemtables),
 		writeCh:       make(chan *request, kvWriteChCapacity),
 		opt:           opt,
 		manifest:      manifestFile,
-		elog:          trace.NewEventLog("Badger", "DB"),
+		elog:          elog,
 		dirLockGuard:  dirLockGuard,
 		valueDirGuard: valueDirLockGuard,
 		orc:           newOracle(opt),
@@ -319,7 +324,7 @@ func Open(opt Options) (db *DB, err error) {
 	replayCloser := y.NewCloser(1)
 	go db.doWrites(replayCloser)
 
-	if err = db.vlog.open(db, vptr, db.replayFunction()); err != nil {
+	if err = db.vlog.open(db, vptr, db.replayFunction(), opt.EventLogging); err != nil {
 		return db, y.Wrapf(err, "During db.vlog.open")
 	}
 	replayCloser.SignalAndWait() // Wait for replay to be applied first.

event_log.go

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2019 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package badger
+
+import "golang.org/x/net/trace"
+
+var (
+	noEventLog trace.EventLog = nilEventLog{}
+)
+
+type nilEventLog struct{}
+
+func (nel nilEventLog) Printf(format string, a ...interface{}) {}
+
+func (nel nilEventLog) Errorf(format string, a ...interface{}) {}
+
+func (nel nilEventLog) Finish() {}

options.go

@@ -44,6 +44,7 @@ type Options struct {
 	ReadOnly            bool
 	Truncate            bool
 	Logger              Logger
+	EventLogging        bool
 
 	// Fine tuning options.
 
@@ -114,6 +115,7 @@ func DefaultOptions(path string) Options {
 		ValueThreshold:     32,
 		Truncate:           false,
 		Logger:             defaultLogger,
+		EventLogging:       true,
 		LogRotatesToFlush:  2,
 	}
 }
@@ -237,6 +239,16 @@ func (opt Options) WithLogger(val Logger) Options {
 	return opt
 }
 
+// WithEventLogging returns a new Options value with EventLogging set to the given value.
+//
+// EventLogging provides a way to enable or disable trace.EventLog logging.
+//
+// The default value of EventLogging is true.
+func (opt Options) WithEventLogging(enabled bool) Options {
+	opt.EventLogging = enabled
+	return opt
+}
+
 // WithMaxTableSize returns a new Options value with MaxTableSize set to the given value.
 //
 // MaxTableSize sets the maximum size in bytes for each LSM table or file.

value.go

@@ -787,12 +787,15 @@ func (vlog *valueLog) replayLog(lf *logFile, offset uint32, replayFn logEntry) e
 	return nil
 }
 
-func (vlog *valueLog) open(db *DB, ptr valuePointer, replayFn logEntry) error {
+func (vlog *valueLog) open(db *DB, ptr valuePointer, replayFn logEntry, eventLogging bool) error {
 	opt := db.opt
 	vlog.opt = opt
 	vlog.dirPath = opt.ValueDir
 	vlog.db = db
-	vlog.elog = trace.NewEventLog("Badger", "Valuelog")
+	vlog.elog = noEventLog
+	if eventLogging {
+		vlog.elog = trace.NewEventLog("Badger", "Valuelog")
+	}
 	vlog.garbageCh = make(chan struct{}, 1) // Only allow one GC at a time.
 	vlog.lfDiscardStats = &lfDiscardStats{m: make(map[uint32]int64)}
 	if err := vlog.populateFilesMap(); err != nil {

value_test.go

@@ -405,7 +405,7 @@ func TestValueGC4(t *testing.T) {
 	err = kv.vlog.Close()
 	require.NoError(t, err)
 
-	err = kv.vlog.open(kv, valuePointer{Fid: 2}, kv.replayFunction())
+	err = kv.vlog.open(kv, valuePointer{Fid: 2}, kv.replayFunction(), true)
 	require.NoError(t, err)
 
 	for i := 0; i < 8; i++ {
@@ -628,7 +628,7 @@ func TestPartialAppendToValueLog(t *testing.T) {
 	// Replay value log from beginning, badger head is past k2.
 	require.NoError(t, kv.vlog.Close())
 	require.NoError(t,
-		kv.vlog.open(kv, valuePointer{Fid: 0}, kv.replayFunction()))
+		kv.vlog.open(kv, valuePointer{Fid: 0}, kv.replayFunction(), true))
 	require.NoError(t, kv.Close())
 }