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Merge pull request #755 from SiaFoundation/pj/migration-estimates
Migration Estimates
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,121 @@ | ||
| package stats | ||
|
|
||
| import ( | ||
| "math" | ||
| "sync" | ||
| "time" | ||
|
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| "github.com/montanaflynn/stats" | ||
| ) | ||
|
|
||
| const ( | ||
| statsDecayHalfTime = 10 * time.Minute | ||
| statsDecayThreshold = 5 * time.Minute | ||
| ) | ||
|
|
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| type ( | ||
| DataPoints struct { | ||
| stats.Float64Data | ||
| halfLife time.Duration | ||
| size int | ||
|
|
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| mu sync.Mutex | ||
| cnt int | ||
| p90 float64 | ||
| lastDatapoint time.Time | ||
| lastDecay time.Time | ||
| } | ||
|
|
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| Float64Data = stats.Float64Data | ||
| ) | ||
|
|
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| func Default() *DataPoints { | ||
| return New(statsDecayHalfTime) | ||
| } | ||
|
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| func NoDecay() *DataPoints { | ||
| return New(0) | ||
| } | ||
|
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| func New(halfLife time.Duration) *DataPoints { | ||
| return &DataPoints{ | ||
| size: 1000, | ||
| Float64Data: make([]float64, 0), | ||
| halfLife: halfLife, | ||
| lastDecay: time.Now(), | ||
| } | ||
| } | ||
|
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| func (a *DataPoints) Average() float64 { | ||
| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
| avg, err := a.Mean() | ||
| if err != nil { | ||
| avg = 0 | ||
| } | ||
| return avg | ||
| } | ||
|
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| func (a *DataPoints) P90() float64 { | ||
| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
| return a.p90 | ||
| } | ||
|
|
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| func (a *DataPoints) Recompute() { | ||
| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
|
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| // apply decay | ||
| a.tryDecay() | ||
|
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| // recalculate the p90 | ||
| p90, err := a.Percentile(90) | ||
| if err != nil { | ||
| p90 = 0 | ||
| } | ||
| a.p90 = p90 | ||
| } | ||
|
|
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| func (a *DataPoints) Track(p float64) { | ||
| a.mu.Lock() | ||
| defer a.mu.Unlock() | ||
|
|
||
| if a.cnt < a.size { | ||
| a.Float64Data = append(a.Float64Data, p) | ||
| } else { | ||
| a.Float64Data[a.cnt%a.size] = p | ||
| } | ||
|
|
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| a.lastDatapoint = time.Now() | ||
| a.cnt++ | ||
| } | ||
|
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| func (a *DataPoints) tryDecay() { | ||
| // return if decay is disabled | ||
| if a.halfLife == 0 { | ||
| return | ||
| } | ||
|
|
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| // return if decay is not needed | ||
| if time.Since(a.lastDatapoint) < statsDecayThreshold { | ||
| return | ||
| } | ||
|
|
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| // return if decay is not due | ||
| decayFreq := a.halfLife / 5 | ||
| timePassed := time.Since(a.lastDecay) | ||
| if timePassed < decayFreq { | ||
| return | ||
| } | ||
|
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| // calculate decay and apply it | ||
| strength := float64(timePassed) / float64(a.halfLife) | ||
| decay := math.Floor(math.Pow(0.5, strength)*100) / 100 // round down to 2 decimals | ||
| for i := range a.Float64Data { | ||
| a.Float64Data[i] *= decay | ||
| } | ||
|
|
||
| // update the last decay time | ||
| a.lastDecay = time.Now() | ||
| } |
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