[skip ci]add timerecord for debug (#5729)

* add timerecord for debug

Signed-off-by: yudong.cai <yudong.cai@zilliz.com>

* update comments

Signed-off-by: yudong.cai <yudong.cai@zilliz.com>

internal/util/timerecord/time_recorder.go

@@ -0,0 +1,63 @@
+// Copyright (C) 2019-2020 Zilliz. All rights reserved.
+//
+// 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 timerecord
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/milvus-io/milvus/internal/log"
+)
+
+type TimeRecorder struct {
+	header string
+	start  time.Time
+	last   time.Time
+}
+
+// NewTimeRecorder create a new TimeRecorder
+func NewTimeRecorder(header string) *TimeRecorder {
+	return &TimeRecorder{
+		header: header,
+		start:  time.Now(),
+		last:   time.Now(),
+	}
+}
+
+// Record calculates the time span from previous Record call
+func (tr *TimeRecorder) Record(msg string) time.Duration {
+	curr := time.Now()
+	span := curr.Sub(tr.last)
+	tr.last = curr
+	tr.printTimeRecord(msg, span)
+	return span
+}
+
+// Elapse calculates the time span from the beginning of this TimeRecorder
+func (tr *TimeRecorder) Elapse(msg string) time.Duration {
+	curr := time.Now()
+	span := curr.Sub(tr.start)
+	tr.printTimeRecord(msg, span)
+	return span
+}
+
+func (tr *TimeRecorder) printTimeRecord(msg string, span time.Duration) {
+	str := ""
+	if len(tr.header) != 0 {
+		str += tr.header + ": "
+	}
+	str += msg
+	str += " ("
+	str += strconv.Itoa(int(span.Milliseconds()))
+	str += "ms)"
+	log.Debug(str)
+}