Flow: Improve Kubernetes log collection #5623
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| package kubetail | ||
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| import ( | ||
| "sync" | ||
| "time" | ||
| ) | ||
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| // rollingAverageCalculator calculates a rolling average between points in | ||
| // time. | ||
| // | ||
| // rollingAverageCalculator stores a circular buffer where the difference | ||
| // between timestamps are kept. | ||
| type rollingAverageCalculator struct { | ||
| mtx sync.Mutex | ||
| window []time.Duration | ||
| windowSize int | ||
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| minEntries int | ||
| minDuration time.Duration | ||
| defaultDuration time.Duration | ||
|
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| currentIndex int | ||
| prevTimestamp time.Time | ||
| } | ||
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| func newRollingAverageCalculator(windowSize, minEntries int, minDuration, defaultDuration time.Duration) *rollingAverageCalculator { | ||
| return &rollingAverageCalculator{ | ||
| windowSize: windowSize, | ||
| window: make([]time.Duration, windowSize), | ||
| minEntries: minEntries, | ||
| minDuration: minDuration, | ||
| defaultDuration: defaultDuration, | ||
| currentIndex: -1, | ||
| } | ||
| } | ||
|
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| // AddTimestamp adds a new timestamp to the rollingAverageCalculator. If there | ||
| // is a previous timestamp, the difference between timestamps is calculated and | ||
| // stored in the window. | ||
| func (r *rollingAverageCalculator) AddTimestamp(timestamp time.Time) { | ||
| r.mtx.Lock() | ||
| defer func() { | ||
| r.prevTimestamp = timestamp | ||
| r.mtx.Unlock() | ||
| }() | ||
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| // First timestamp | ||
| if r.currentIndex == -1 && r.prevTimestamp.Equal(time.Time{}) { | ||
| return | ||
| } | ||
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| r.currentIndex++ | ||
| if r.currentIndex >= r.windowSize { | ||
| r.currentIndex = 0 | ||
| } | ||
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| r.window[r.currentIndex] = timestamp.Sub(r.prevTimestamp) | ||
| } | ||
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| // GetAverage calculates the average of all the durations in the window. | ||
| func (r *rollingAverageCalculator) GetAverage() time.Duration { | ||
| r.mtx.Lock() | ||
| defer r.mtx.Unlock() | ||
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| var total time.Duration | ||
| count := 0 | ||
| for _, v := range r.window { | ||
| if v != 0 { | ||
| total += v | ||
| count++ | ||
| } | ||
| } | ||
| if count == 0 || count < r.minEntries { | ||
| return r.defaultDuration | ||
| } | ||
| d := total / time.Duration(count) | ||
| if d < r.minDuration { | ||
| return r.minDuration | ||
| } | ||
| return d | ||
| } | ||
|
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| // GetLast gets the last timestamp added to the rollingAverageCalculator. | ||
| func (r *rollingAverageCalculator) GetLast() time.Time { | ||
| r.mtx.Lock() | ||
| defer r.mtx.Unlock() | ||
|
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| return r.prevTimestamp | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| package kubetail | ||
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| import ( | ||
| "testing" | ||
| "time" | ||
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| func Test(t *testing.T) { | ||
| tests := []struct { | ||
| name string | ||
| windowSize int | ||
| minEntries int | ||
| input []int64 | ||
| expected time.Duration | ||
| }{ | ||
| { | ||
| name: "empty, expect default", | ||
| windowSize: 10, | ||
| input: []int64{}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "one sample, not enough, expect default", | ||
| windowSize: 5, | ||
| input: []int64{10}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "partially full", | ||
| windowSize: 10, | ||
| input: []int64{10, 20, 30, 40, 50}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "completely full", | ||
| windowSize: 5, | ||
| input: []int64{10, 20, 30, 40, 50, 60}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "rollover simple", | ||
| windowSize: 5, | ||
| input: []int64{10, 20, 30, 40, 50, 60}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "rollover complex: make sure first value is ignored", | ||
| windowSize: 5, | ||
| input: []int64{0, 40, 50, 60, 70, 80, 90}, | ||
| expected: time.Duration(10), | ||
| }, | ||
| { | ||
| name: "complex", | ||
| windowSize: 5, | ||
| // 40 +1 +4 +45 +5 = 95, 95/5 = 19 | ||
| input: []int64{10, 50, 51, 55, 100, 105}, | ||
| expected: time.Duration(19), | ||
| }, | ||
| { | ||
| name: "complex 2", | ||
| windowSize: 10, | ||
| // outside of window | | ||
| // 40 +1 +4 +45 +|5 +5 +90 +100 +150 +300 +5 +45 +50 +149 = 899 | ||
| input: []int64{10, 50, 51, 55, 100, 105, 110, 200, 300, 450, 750, 755, 800, 850, 999}, | ||
| expected: time.Duration(89), // Integer math result is truncated not rounded. | ||
| }, | ||
| { | ||
| name: "below min duration", | ||
| windowSize: 5, | ||
| input: []int64{0, 1, 2, 3, 4, 5, 6}, | ||
| expected: time.Duration(2), | ||
| }, | ||
| } | ||
| for _, test := range tests { | ||
| t.Run(test.name, func(t *testing.T) { | ||
| c := newRollingAverageCalculator(test.windowSize, test.minEntries, time.Duration(2), time.Duration(10)) | ||
| for _, v := range test.input { | ||
| c.AddTimestamp(time.Unix(0, v)) | ||
| } | ||
| avg := c.GetAverage() | ||
| assert.Equal(t, test.expected, avg) | ||
| }) | ||
| } | ||
| } |
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In what situations will PrepareLabels error? Is there a case where we discard a target and increment a counter or something?
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Looks like it fails based on validations:
In this particular case, the component would've been given a bad target.