Enable customization of metrics calculation

flow_test.go

@@ -13,7 +13,7 @@ func TestBasic(t *testing.T) {
 		m.Mark(1000)
 		mockClock.Add(40 * time.Millisecond)
 	}
-	if rate := m.Snapshot().Rate; rate != 25000 {
+	if rate := m.Snapshot().Rate; !approxEq(rate, 25000, 1) {
 		t.Errorf("expected rate 25000, got %f", rate)
 	}
 
@@ -99,7 +99,7 @@ func TestUnregister(t *testing.T) {
 	}
 
 	actual := m.Snapshot()
-	if actual.Rate != 10 {
+	if !approxEq(actual.Rate, 10, 1) {
 		t.Errorf("expected rate 10, got %f", actual.Rate)
 	}
 
@@ -120,7 +120,7 @@ func TestUnregister(t *testing.T) {
 	}
 
 	actual = m.Snapshot()
-	if actual.Rate != 20 {
+	if !approxEq(actual.Rate, 20, 1) {
 		t.Errorf("expected rate 20, got %f", actual.Rate)
 	}
 

meter.go

@@ -2,23 +2,46 @@ package flow
 
 import (
 	"fmt"
+	"math"
 	"sync/atomic"
 	"time"
 )
 
+// IdleRate the rate at which we declare a meter idle (and stop tracking it
+// until it's re-registered).
+//
+// The default ensures that 1 event every ~30s will keep the meter from going
+// idle.
+var IdleRate = 1e-13
+
+// Alpha for EWMA of 1s
+var alpha = 1 - math.Exp(-1.0)
+
 // Snapshot is a rate/total snapshot.
 type Snapshot struct {
 	Rate       float64
 	Total      uint64
 	LastUpdate time.Time
 }
 
+type MeterInterface interface {
+	String() string
+	Mark(count uint64)
+	Snapshot() Snapshot
+	Reset()
+	Update(tdiff time.Duration)
+	IsIdle() bool
+	SetIdle()
+	SetActive()
+}
+
 // NewMeter returns a new Meter with the correct idle time.
 //
 // While zero-value Meters can be used, their "last update" time will start at
 // the program start instead of when the meter was created.
-func NewMeter() *Meter {
+func NewMeter() MeterInterface {
 	return &Meter{
+		fresh: true,
 		snapshot: Snapshot{
 			LastUpdate: cl.Now(),
 		},
@@ -38,6 +61,8 @@ type Meter struct {
 
 	// Take lock.
 	snapshot Snapshot
+
+	fresh bool
 }
 
 // Mark updates the total.
@@ -69,3 +94,85 @@ func (m *Meter) Reset() {
 func (m *Meter) String() string {
 	return m.Snapshot().String()
 }
+
+func (m *Meter) Update(tdiff time.Duration) {
+	if !m.fresh {
+		timeMultiplier := float64(time.Second) / float64(tdiff)
+		total := m.accumulator.Load()
+		diff := total - m.snapshot.Total
+		instant := timeMultiplier * float64(diff)
+
+		if diff > 0 {
+			m.snapshot.LastUpdate = cl.Now()
+		}
+
+		if m.snapshot.Rate == 0 {
+			m.snapshot.Rate = instant
+		} else {
+			m.snapshot.Rate += alpha * (instant - m.snapshot.Rate)
+		}
+		m.snapshot.Total = total
+
+		// This is equivalent to one zeros, then one, then 30 zeros.
+		// We'll consider that to be "idle".
+		if m.snapshot.Rate > IdleRate {
+			return
+		}
+
+		// Ok, so we are idle...
+		// Mark this as idle by zeroing the accumulator.
+		swappedTotal := m.accumulator.Swap(0)
+		// So..., are we really idle?
+		if swappedTotal > total {
+			// Not so idle...
+			// Now we need to make sure this gets re-registered.
+
+			// First, add back what we removed. If we can do this
+			// fast enough, we can put it back before anyone
+			// notices.
+			currentTotal := m.accumulator.Add(swappedTotal)
+
+			// Did we make it?
+			if currentTotal == swappedTotal {
+				// Yes! Nobody noticed, move along.
+				return
+			}
+			// No. Someone noticed and will (or has) put back into
+			// the registration channel.
+			//
+			// Remove the snapshot total, it'll get added back on
+			// registration.
+			//
+			// `^uint64(total - 1)` is the two's complement of
+			// `total`. It's the "correct" way to subtract
+			// atomically in go.
+			m.accumulator.Add(^uint64(m.snapshot.Total - 1))
+		} else {
+			m.SetIdle()
+		}
+	} else {
+		// Re-add the total to all the newly active accumulators and set the snapshot to the total.
+		// 1. We don't do this on register to avoid having to take the snapshot lock.
+		// 2. We skip calculating the bandwidth for this round so we get an _accurate_ bandwidth calculation.
+		total := m.accumulator.Add(m.snapshot.Total)
+		if total > m.snapshot.Total {
+			m.snapshot.LastUpdate = cl.Now()
+		}
+		m.snapshot.Total = total
+		m.fresh = false
+	}
+}
+
+func (m *Meter) IsIdle() bool {
+	return !m.registered
+}
+
+func (m *Meter) SetIdle() {
+	m.snapshot.Rate = 0
+	m.registered = false
+	m.fresh = true
+}
+
+func (m *Meter) SetActive() {
+	m.registered = true
+}

mockclocktest/mock_clock_test.go

@@ -0,0 +1,48 @@
+package mockclocktest
+
+import (
+	"math"
+	"testing"
+	"time"
+
+	flow "github.com/libp2p/go-flow-metrics"
+
+	"github.com/benbjohnson/clock"
+)
+
+var cl = clock.NewMock()
+
+func init() {
+	flow.SetClock(cl)
+}
+
+func TestBasic(t *testing.T) {
+	m := new(flow.Meter)
+	for i := 0; i < 300; i++ {
+		m.Mark(1000)
+		cl.Add(40 * time.Millisecond)
+	}
+	if rate := m.Snapshot().Rate; approxEq(rate, 25000, 1) {
+		t.Errorf("expected rate 25000, got %f", rate)
+	}
+
+	for i := 0; i < 200; i++ {
+		m.Mark(200)
+		cl.Add(40 * time.Millisecond)
+	}
+
+	// Adjusts
+	if rate := m.Snapshot().Rate; approxEq(rate, 5017.776503840969, 0.0001) {
+		t.Errorf("expected rate 5017.776503840969, got %f", rate)
+	}
+
+	// Let it settle.
+	cl.Add(2 * time.Second)
+	if total := m.Snapshot().Total; total != 340000 {
+		t.Errorf("expected total 3400000, got %d", total)
+	}
+}
+
+func approxEq(a, b, err float64) bool {
+	return math.Abs(a-b) < err
+}

registry.go

@@ -11,12 +11,12 @@ type MeterRegistry struct {
 }
 
 // Get gets (or creates) a meter by name.
-func (r *MeterRegistry) Get(name string) *Meter {
+func (r *MeterRegistry) Get(name string) MeterInterface {
 	if m, ok := r.meters.Load(name); ok {
-		return m.(*Meter)
+		return m.(MeterInterface)
 	}
 	m, _ := r.meters.LoadOrStore(name, NewMeter())
-	return m.(*Meter)
+	return m.(MeterInterface)
 }
 
 // FindIdle finds all meters that haven't been used since the given time.
@@ -50,7 +50,7 @@ func (r *MeterRegistry) walkIdle(since time.Time, cb func(key interface{})) {
 
 	r.meters.Range(func(k, v interface{}) bool {
 		// So, this _is_ slightly inaccurate.
-		if v.(*Meter).snapshot.LastUpdate.Before(since) {
+		if v.(MeterInterface).Snapshot().LastUpdate.Before(since) {
 			cb(k)
 		}
 		return true
@@ -66,9 +66,9 @@ func (r *MeterRegistry) Remove(name string) {
 }
 
 // ForEach calls the passed function for each registered meter.
-func (r *MeterRegistry) ForEach(iterFunc func(string, *Meter)) {
+func (r *MeterRegistry) ForEach(iterFunc func(string, MeterInterface)) {
 	r.meters.Range(func(k, v interface{}) bool {
-		iterFunc(k.(string), v.(*Meter))
+		iterFunc(k.(string), v.(MeterInterface))
 		return true
 	})
 }

registry_test.go

@@ -31,11 +31,11 @@ func TestRegistry(t *testing.T) {
 		t.Errorf("expected the last update (%s) to have after (%s)", lu, m1Update)
 	}
 
-	expectedMeters := map[string]*Meter{
+	expectedMeters := map[string]MeterInterface{
 		"first":  m1,
 		"second": m2,
 	}
-	r.ForEach(func(n string, m *Meter) {
+	r.ForEach(func(n string, m MeterInterface) {
 		if expectedMeters[n] != m {
 			t.Errorf("wrong meter '%s'", n)
 		}
@@ -48,7 +48,7 @@ func TestRegistry(t *testing.T) {
 	r.Remove("first")
 
 	found := false
-	r.ForEach(func(n string, m *Meter) {
+	r.ForEach(func(n string, m MeterInterface) {
 		if n != "second" {
 			t.Errorf("found unexpected meter: %s", n)
 			return
@@ -71,11 +71,11 @@ func TestRegistry(t *testing.T) {
 		t.Errorf("expected first total to now be 0, got %d", total)
 	}
 
-	expectedMeters = map[string]*Meter{
+	expectedMeters = map[string]MeterInterface{
 		"first":  m3,
 		"second": m2,
 	}
-	r.ForEach(func(n string, m *Meter) {
+	r.ForEach(func(n string, m MeterInterface) {
 		if expectedMeters[n] != m {
 			t.Errorf("wrong meter '%s'", n)
 		}
@@ -115,7 +115,7 @@ func TestClearRegistry(t *testing.T) {
 
 	r.Clear()
 
-	r.ForEach(func(n string, _m *Meter) {
+	r.ForEach(func(n string, _m MeterInterface) {
 		t.Errorf("expected no meters at all, found a meter %s", n)
 	})