txthrottler: move ThrottlerInterface to go/vt/throttler, use slices pkg, add stats

go/vt/throttler/demo/throttler_demo.go

@@ -103,7 +103,7 @@ type replica struct {
 
 	// throttler is used to enforce the maximum rate at which replica applies
 	// transactions. It must not be confused with the client's throttler.
-	throttler         *throttler.Throttler
+	throttler         throttler.Throttler
 	lastHealthUpdate  time.Time
 	lagUpdateInterval time.Duration
 
@@ -226,7 +226,7 @@ type client struct {
 	primary *primary
 
 	healthCheck discovery.HealthCheck
-	throttler   *throttler.Throttler
+	throttler   throttler.Throttler
 
 	stopChan      chan struct{}
 	wg            sync.WaitGroup

go/vt/throttler/manager.go

@@ -64,16 +64,16 @@ type managerImpl struct {
 	// mu guards all fields in this group.
 	mu sync.Mutex
 	// throttlers tracks all running throttlers (by their name).
-	throttlers map[string]*Throttler
+	throttlers map[string]Throttler
 }
 
 func newManager() *managerImpl {
 	return &managerImpl{
-		throttlers: make(map[string]*Throttler),
+		throttlers: make(map[string]Throttler),
 	}
 }
 
-func (m *managerImpl) registerThrottler(name string, throttler *Throttler) error {
+func (m *managerImpl) registerThrottler(name string, throttler Throttler) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
@@ -207,7 +207,7 @@ func (m *managerImpl) throttlerNamesLocked() []string {
 
 // log returns the most recent changes of the MaxReplicationLag module.
 // There will be one result for each processed replication lag record.
-func (m *managerImpl) log(throttlerName string) ([]result, error) {
+func (m *managerImpl) log(throttlerName string) ([]Result, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
@@ -216,5 +216,5 @@ func (m *managerImpl) log(throttlerName string) ([]result, error) {
 		return nil, fmt.Errorf("throttler: %v does not exist", throttlerName)
 	}
 
-	return t.log(), nil
+	return t.Log(), nil
 }

go/vt/throttler/manager_test.go

@@ -37,7 +37,7 @@ var (
 
 type managerTestFixture struct {
 	m      *managerImpl
-	t1, t2 *Throttler
+	t1, t2 Throttler
 }
 
 func (f *managerTestFixture) setUp() error {

go/vt/throttler/max_replication_lag_module.go

@@ -313,7 +313,7 @@ func (m *MaxReplicationLagModule) recalculateRate(lagRecordNow replicationLagRec
 
 	m.memory.ageBadRate(now)
 
-	r := result{
+	r := Result{
 		Now:            now,
 		RateChange:     unchangedRate,
 		lastRateChange: m.lastRateChange,
@@ -446,7 +446,7 @@ func stateGreater(a, b state) bool {
 // and we should not skip the current replica ("lagRecordNow").
 // Even if it's the same replica we may skip it and return false because
 // we want to wait longer for the propagation of the current rate change.
-func (m *MaxReplicationLagModule) isReplicaUnderTest(r *result, now time.Time, testedState state, lagRecordNow replicationLagRecord) bool {
+func (m *MaxReplicationLagModule) isReplicaUnderTest(r *Result, now time.Time, testedState state, lagRecordNow replicationLagRecord) bool {
 	if m.replicaUnderTest == nil {
 		return true
 	}
@@ -472,7 +472,7 @@ func (m *MaxReplicationLagModule) isReplicaUnderTest(r *result, now time.Time, t
 	return true
 }
 
-func (m *MaxReplicationLagModule) increaseRate(r *result, now time.Time, lagRecordNow replicationLagRecord) {
+func (m *MaxReplicationLagModule) increaseRate(r *Result, now time.Time, lagRecordNow replicationLagRecord) {
 	m.markCurrentRateAsBadOrGood(r, now, stateIncreaseRate, unknown)
 
 	oldRate := m.rate.Load()
@@ -560,7 +560,7 @@ func (m *MaxReplicationLagModule) minTestDurationUntilNextIncrease(increase floa
 	return minDuration
 }
 
-func (m *MaxReplicationLagModule) decreaseAndGuessRate(r *result, now time.Time, lagRecordNow replicationLagRecord) {
+func (m *MaxReplicationLagModule) decreaseAndGuessRate(r *Result, now time.Time, lagRecordNow replicationLagRecord) {
 	// Guess replication rate based on the difference in the replication lag of this
 	// particular replica.
 	lagRecordBefore := m.lagCache(lagRecordNow).atOrAfter(discovery.TabletToMapKey(lagRecordNow.Tablet), m.lastRateChange)
@@ -631,7 +631,7 @@ func (m *MaxReplicationLagModule) decreaseAndGuessRate(r *result, now time.Time,
 // guessReplicationRate guesses the actual replication rate based on the new bac
 // Note that "lagDifference" can be positive (lag increased) or negative (lag
 // decreased).
-func (m *MaxReplicationLagModule) guessReplicationRate(r *result, avgPrimaryRate float64, lagBefore, lagNow int64, lagDifference, d time.Duration) (int64, string) {
+func (m *MaxReplicationLagModule) guessReplicationRate(r *Result, avgPrimaryRate float64, lagBefore, lagNow int64, lagDifference, d time.Duration) (int64, string) {
 	// avgReplicationRate is the average rate (per second) at which the replica
 	// applied transactions from the replication stream. We infer the value
 	// from the relative change in the replication lag.
@@ -676,14 +676,14 @@ func (m *MaxReplicationLagModule) guessReplicationRate(r *result, avgPrimaryRate
 	return int64(newRate), reason
 }
 
-func (m *MaxReplicationLagModule) emergency(r *result, now time.Time, lagRecordNow replicationLagRecord) {
+func (m *MaxReplicationLagModule) emergency(r *Result, now time.Time, lagRecordNow replicationLagRecord) {
 	m.markCurrentRateAsBadOrGood(r, now, stateEmergency, unknown)
 
 	decreaseReason := fmt.Sprintf("replication lag went beyond max: %d > %d", lagRecordNow.lag(), m.config.MaxReplicationLagSec)
 	m.decreaseRateByPercentage(r, now, lagRecordNow, stateEmergency, m.config.EmergencyDecrease, decreaseReason)
 }
 
-func (m *MaxReplicationLagModule) decreaseRateByPercentage(r *result, now time.Time, lagRecordNow replicationLagRecord, newState state, decrease float64, decreaseReason string) {
+func (m *MaxReplicationLagModule) decreaseRateByPercentage(r *Result, now time.Time, lagRecordNow replicationLagRecord, newState state, decrease float64, decreaseReason string) {
 	oldRate := m.rate.Load()
 	rate := int64(float64(oldRate) - float64(oldRate)*decrease)
 	if rate == 0 {
@@ -695,7 +695,7 @@ func (m *MaxReplicationLagModule) decreaseRateByPercentage(r *result, now time.T
 	m.updateRate(r, newState, rate, reason, now, lagRecordNow, m.config.MinDurationBetweenDecreases())
 }
 
-func (m *MaxReplicationLagModule) updateRate(r *result, newState state, rate int64, reason string, now time.Time, lagRecordNow replicationLagRecord, testDuration time.Duration) {
+func (m *MaxReplicationLagModule) updateRate(r *Result, newState state, rate int64, reason string, now time.Time, lagRecordNow replicationLagRecord, testDuration time.Duration) {
 	oldRate := m.rate.Load()
 
 	m.currentState = newState
@@ -723,7 +723,7 @@ func (m *MaxReplicationLagModule) updateRate(r *result, newState state, rate int
 
 // markCurrentRateAsBadOrGood determines the actual rate between the last rate
 // change and "now" and determines if that rate was bad or good.
-func (m *MaxReplicationLagModule) markCurrentRateAsBadOrGood(r *result, now time.Time, newState state, replicationLagChange replicationLagChange) {
+func (m *MaxReplicationLagModule) markCurrentRateAsBadOrGood(r *Result, now time.Time, newState state, replicationLagChange replicationLagChange) {
 	if m.lastRateChange.IsZero() {
 		// Module was just started. We don't have any data points yet.
 		r.GoodOrBad = ignoredRate
@@ -797,6 +797,6 @@ func (m *MaxReplicationLagModule) markCurrentRateAsBadOrGood(r *result, now time
 	}
 }
 
-func (m *MaxReplicationLagModule) log() []result {
+func (m *MaxReplicationLagModule) log() []Result {
 	return m.results.latestValues()
 }

go/vt/throttler/result.go

@@ -50,10 +50,10 @@ state (old/tested/new): {{.OldState}}/{{.TestedState}}/{{.NewState}}
 lag before: {{.LagBefore}} ({{.AgeOfBeforeLag}} ago) rates (primary/replica): {{.PrimaryRate}}/{{.GuessedReplicationRate}} backlog (old/new): {{.GuessedReplicationBacklogOld}}/{{.GuessedReplicationBacklogNew}}
 reason: {{.Reason}}`))
 
-// result is generated by the MaxReplicationLag module for each processed
+// Result is generated by the MaxReplicationLag module for each processed
 // "replicationLagRecord".
 // It captures the details and the decision of the processing.
-type result struct {
+type Result struct {
 	Now            time.Time
 	RateChange     rateChange
 	lastRateChange time.Time
@@ -80,33 +80,33 @@ type result struct {
 	GuessedReplicationBacklogNew int
 }
 
-func (r result) String() string {
+func (r Result) String() string {
 	var b strings.Builder
 	if err := resultStringTemplate.Execute(&b, r); err != nil {
 		panic(fmt.Sprintf("failed to Execute() template: %v", err))
 	}
 	return b.String()
 }
 
-func (r result) Alias() string {
+func (r Result) Alias() string {
 	return topoproto.TabletAliasString(r.LagRecordNow.Tablet.Alias)
 }
 
-func (r result) TimeSinceLastRateChange() string {
+func (r Result) TimeSinceLastRateChange() string {
 	if r.lastRateChange.IsZero() {
 		return "n/a"
 	}
 	return fmt.Sprintf("%.1fs", r.Now.Sub(r.lastRateChange).Seconds())
 }
 
-func (r result) LagBefore() string {
+func (r Result) LagBefore() string {
 	if r.LagRecordBefore.isZero() {
 		return "n/a"
 	}
 	return fmt.Sprintf("%ds", r.LagRecordBefore.Stats.ReplicationLagSeconds)
 }
 
-func (r result) AgeOfBeforeLag() string {
+func (r Result) AgeOfBeforeLag() string {
 	if r.LagRecordBefore.isZero() {
 		return "n/a"
 	}
@@ -123,18 +123,18 @@ type resultRing struct {
 	// started reusing entries.
 	wrapped bool
 	// values is the underlying ring buffer.
-	values []result
+	values []Result
 }
 
 // newResultRing creates a new resultRing.
 func newResultRing(capacity int) *resultRing {
 	return &resultRing{
-		values: make([]result, capacity),
+		values: make([]Result, capacity),
 	}
 }
 
 // add inserts a new result into the ring buffer.
-func (rr *resultRing) add(r result) {
+func (rr *resultRing) add(r Result) {
 	rr.mu.Lock()
 	defer rr.mu.Unlock()
 
@@ -148,7 +148,7 @@ func (rr *resultRing) add(r result) {
 
 // latestValues returns all values of the buffer. Entries are sorted in reverse
 // chronological order i.e. newer items come first.
-func (rr *resultRing) latestValues() []result {
+func (rr *resultRing) latestValues() []Result {
 	rr.mu.Lock()
 	defer rr.mu.Unlock()
 
@@ -162,7 +162,7 @@ func (rr *resultRing) latestValues() []result {
 		count = rr.position
 	}
 
-	results := make([]result, count)
+	results := make([]Result, count)
 	for i := 0; i < count; i++ {
 		pos := start - i
 		if pos < 0 {

go/vt/throttler/result_test.go

@@ -24,7 +24,7 @@ import (
 )
 
 var (
-	resultIncreased = result{
+	resultIncreased = Result{
 		Now:                          sinceZero(1234 * time.Millisecond),
 		RateChange:                   increasedRate,
 		lastRateChange:               sinceZero(1 * time.Millisecond),
@@ -46,7 +46,7 @@ var (
 		GuessedReplicationBacklogOld: 0,
 		GuessedReplicationBacklogNew: 0,
 	}
-	resultDecreased = result{
+	resultDecreased = Result{
 		Now:                          sinceZero(5000 * time.Millisecond),
 		RateChange:                   decreasedRate,
 		lastRateChange:               sinceZero(1234 * time.Millisecond),
@@ -68,7 +68,7 @@ var (
 		GuessedReplicationBacklogOld: 10,
 		GuessedReplicationBacklogNew: 20,
 	}
-	resultEmergency = result{
+	resultEmergency = Result{
 		Now:                          sinceZero(10123 * time.Millisecond),
 		RateChange:                   decreasedRate,
 		lastRateChange:               sinceZero(5000 * time.Millisecond),
@@ -94,7 +94,7 @@ var (
 
 func TestResultString(t *testing.T) {
 	testcases := []struct {
-		r    result
+		r    Result
 		want string
 	}{
 		{
@@ -134,24 +134,24 @@ reason: emergency state decreased the rate`,
 
 func TestResultRing(t *testing.T) {
 	// Test data.
-	r1 := result{Reason: "r1"}
-	r2 := result{Reason: "r2"}
-	r3 := result{Reason: "r3"}
+	r1 := Result{Reason: "r1"}
+	r2 := Result{Reason: "r2"}
+	r3 := Result{Reason: "r3"}
 
 	rr := newResultRing(2)
 
 	// Use the ring partially.
 	rr.add(r1)
-	got, want := rr.latestValues(), []result{r1}
+	got, want := rr.latestValues(), []Result{r1}
 	require.Equal(t, want, got, "items not correctly added to resultRing")
 
 	// Use it fully.
 	rr.add(r2)
-	got, want = rr.latestValues(), []result{r2, r1}
+	got, want = rr.latestValues(), []Result{r2, r1}
 	require.Equal(t, want, got, "items not correctly added to resultRing")
 
 	// Let it wrap.
 	rr.add(r3)
-	got, want = rr.latestValues(), []result{r3, r2}
+	got, want = rr.latestValues(), []Result{r3, r2}
 	require.Equal(t, want, got, "resultRing did not wrap correctly")
 }