Initial commit

vendor/github.com/cockroachdb/pebble/internal/base/metrics.go

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+// Copyright 2022 The LevelDB-Go and Pebble Authors. All rights reserved. Use
+// of this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+
+package base
+
+import "time"
+
+// ThroughputMetric is used to measure the byte throughput of some component
+// that performs work in a single-threaded manner. The throughput can be
+// approximated by Bytes/(WorkDuration+IdleTime). The idle time is represented
+// separately, so that the user of this metric could approximate the peak
+// throughput as Bytes/WorkTime. The metric is designed to be cumulative (see
+// Merge).
+type ThroughputMetric struct {
+	// Bytes is the processes bytes by the component.
+	Bytes int64
+	// WorkDuration is the duration that the component spent doing work.
+	WorkDuration time.Duration
+	// IdleDuration is the duration that the component was idling, waiting for
+	// work.
+	IdleDuration time.Duration
+}
+
+// Merge accumulates the information from another throughput metric.
+func (tm *ThroughputMetric) Merge(x ThroughputMetric) {
+	tm.Bytes += x.Bytes
+	tm.WorkDuration += x.WorkDuration
+	tm.IdleDuration += x.IdleDuration
+}
+
+// Subtract subtracts the information from another ThroughputMetric
+func (tm *ThroughputMetric) Subtract(x ThroughputMetric) {
+	tm.Bytes -= x.Bytes
+	tm.WorkDuration -= x.WorkDuration
+	tm.IdleDuration -= x.IdleDuration
+}
+
+// PeakRate returns the approximate peak rate if there was no idling.
+func (tm *ThroughputMetric) PeakRate() int64 {
+	if tm.Bytes == 0 {
+		return 0
+	}
+	return int64((float64(tm.Bytes) / float64(tm.WorkDuration)) * float64(time.Second))
+}
+
+// Rate returns the observed rate.
+func (tm *ThroughputMetric) Rate() int64 {
+	if tm.Bytes == 0 {
+		return 0
+	}
+	return int64((float64(tm.Bytes) / float64(tm.WorkDuration+tm.IdleDuration)) *
+		float64(time.Second))
+}
+
+// Utilization returns a percent [0, 1.0] indicating the percent of time
+// work was performed.
+func (tm *ThroughputMetric) Utilization() float64 {
+	if tm.WorkDuration == 0 {
+		return 0
+	}
+	return float64(tm.WorkDuration) / float64(tm.WorkDuration+tm.IdleDuration)
+}
+
+// GaugeSampleMetric is used to measure a gauge value (e.g. queue length) by
+// accumulating samples of that gauge.
+type GaugeSampleMetric struct {
+	// The sum of all the samples.
+	sampleSum int64
+	// The number of samples.
+	count int64
+}
+
+// AddSample adds the given sample.
+func (gsm *GaugeSampleMetric) AddSample(sample int64) {
+	gsm.sampleSum += sample
+	gsm.count++
+}
+
+// Merge accumulates the information from another gauge metric.
+func (gsm *GaugeSampleMetric) Merge(x GaugeSampleMetric) {
+	gsm.sampleSum += x.sampleSum
+	gsm.count += x.count
+}
+
+// Subtract subtracts the information from another gauge metric.
+func (gsm *GaugeSampleMetric) Subtract(x GaugeSampleMetric) {
+	gsm.sampleSum -= x.sampleSum
+	gsm.count -= x.count
+}
+
+// Mean returns the mean value.
+func (gsm *GaugeSampleMetric) Mean() float64 {
+	if gsm.count == 0 {
+		return 0
+	}
+	return float64(gsm.sampleSum) / float64(gsm.count)
+}