1/*
2Copyright 2015 The Kubernetes Authors.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17package trace
18
19import (
20	"bytes"
21	"fmt"
22	"math/rand"
23	"time"
24
25	"k8s.io/klog"
26)
27
28type traceStep struct {
29	stepTime time.Time
30	msg      string
31}
32
33// Trace keeps track of a set of "steps" and allows us to log a specific
34// step if it took longer than its share of the total allowed time
35type Trace struct {
36	name      string
37	startTime time.Time
38	steps     []traceStep
39}
40
41// New creates a Trace with the specified name
42func New(name string) *Trace {
43	return &Trace{name, time.Now(), nil}
44}
45
46// Step adds a new step with a specific message
47func (t *Trace) Step(msg string) {
48	if t.steps == nil {
49		// traces almost always have less than 6 steps, do this to avoid more than a single allocation
50		t.steps = make([]traceStep, 0, 6)
51	}
52	t.steps = append(t.steps, traceStep{time.Now(), msg})
53}
54
55// Log is used to dump all the steps in the Trace
56func (t *Trace) Log() {
57	// an explicit logging request should dump all the steps out at the higher level
58	t.logWithStepThreshold(0)
59}
60
61func (t *Trace) logWithStepThreshold(stepThreshold time.Duration) {
62	var buffer bytes.Buffer
63	tracenum := rand.Int31()
64	endTime := time.Now()
65
66	totalTime := endTime.Sub(t.startTime)
67	buffer.WriteString(fmt.Sprintf("Trace[%d]: %q (started: %v) (total time: %v):\n", tracenum, t.name, t.startTime, totalTime))
68	lastStepTime := t.startTime
69	for _, step := range t.steps {
70		stepDuration := step.stepTime.Sub(lastStepTime)
71		if stepThreshold == 0 || stepDuration > stepThreshold || klog.V(4) {
72			buffer.WriteString(fmt.Sprintf("Trace[%d]: [%v] [%v] %v\n", tracenum, step.stepTime.Sub(t.startTime), stepDuration, step.msg))
73		}
74		lastStepTime = step.stepTime
75	}
76	stepDuration := endTime.Sub(lastStepTime)
77	if stepThreshold == 0 || stepDuration > stepThreshold || klog.V(4) {
78		buffer.WriteString(fmt.Sprintf("Trace[%d]: [%v] [%v] END\n", tracenum, endTime.Sub(t.startTime), stepDuration))
79	}
80
81	klog.Info(buffer.String())
82}
83
84// LogIfLong is used to dump steps that took longer than its share
85func (t *Trace) LogIfLong(threshold time.Duration) {
86	if time.Since(t.startTime) >= threshold {
87		// if any step took more than it's share of the total allowed time, it deserves a higher log level
88		stepThreshold := threshold / time.Duration(len(t.steps)+1)
89		t.logWithStepThreshold(stepThreshold)
90	}
91}
92
93// TotalTime can be used to figure out how long it took since the Trace was created
94func (t *Trace) TotalTime() time.Duration {
95	return time.Since(t.startTime)
96}
97