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refactored all throttling code into throttler.so

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This commit is contained in:
Shlomi Noach 2016-08-30 12:25:45 +02:00
parent 23357d0643
commit b2c71931c6
3 changed files with 307 additions and 270 deletions
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2
go/base/context.go
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@ -136,6 +136,8 @@ type MigrationContext struct {
throttleMutex *sync.Mutex throttleMutex *sync.Mutex
IsPostponingCutOver int64 IsPostponingCutOver int64
CountingRowsFlag int64 CountingRowsFlag int64
AllEventsUpToLockProcessedInjectedFlag int64
CleanupImminentFlag int64
OriginalTableColumns *sql.ColumnList OriginalTableColumns *sql.ColumnList
OriginalTableUniqueKeys [](*sql.UniqueKey) OriginalTableUniqueKeys [](*sql.UniqueKey)

257
go/logic/migrator.go
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@ -20,7 +20,6 @@ import (
"github.com/github/gh-ost/go/base" "github.com/github/gh-ost/go/base"
"github.com/github/gh-ost/go/binlog" "github.com/github/gh-ost/go/binlog"
"github.com/github/gh-ost/go/mysql"
"github.com/github/gh-ost/go/sql" "github.com/github/gh-ost/go/sql"
"github.com/outbrain/golib/log" "github.com/outbrain/golib/log"
@ -66,9 +65,7 @@ type Migrator struct {
panicAbort chan error panicAbort chan error
rowCopyCompleteFlag int64 rowCopyCompleteFlag int64
allEventsUpToLockProcessedInjectedFlag int64
inCutOverCriticalActionFlag int64 inCutOverCriticalActionFlag int64
cleanupImminentFlag int64
userCommandedUnpostponeFlag int64 userCommandedUnpostponeFlag int64
// copyRowsQueue should not be buffered; if buffered some non-damaging but // copyRowsQueue should not be buffered; if buffered some non-damaging but
// excessive work happens at the end of the iteration as new copy-jobs arrive befroe realizing the copy is complete // excessive work happens at the end of the iteration as new copy-jobs arrive befroe realizing the copy is complete
@ -88,8 +85,6 @@ func NewMigrator() *Migrator {
allEventsUpToLockProcessed: make(chan bool), allEventsUpToLockProcessed: make(chan bool),
panicAbort: make(chan error), panicAbort: make(chan error),
allEventsUpToLockProcessedInjectedFlag: 0,
copyRowsQueue: make(chan tableWriteFunc), copyRowsQueue: make(chan tableWriteFunc),
applyEventsQueue: make(chan tableWriteFunc, applyEventsQueueBuffer), applyEventsQueue: make(chan tableWriteFunc, applyEventsQueueBuffer),
handledChangelogStates: make(map[string]bool), handledChangelogStates: make(map[string]bool),
@ -121,160 +116,6 @@ func (this *Migrator) initiateHooksExecutor() (err error) {
return nil return nil
} }
// shouldThrottle performs checks to see whether we should currently be throttling.
// It merely observes the metrics collected by other components, it does not issue
// its own metric collection.
func (this *Migrator) shouldThrottle() (result bool, reason string) {
generalCheckResult := this.migrationContext.GetThrottleGeneralCheckResult()
if generalCheckResult.ShouldThrottle {
return generalCheckResult.ShouldThrottle, generalCheckResult.Reason
}
// Replication lag throttle
maxLagMillisecondsThrottleThreshold := atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold)
lag := atomic.LoadInt64(&this.migrationContext.CurrentLag)
if time.Duration(lag) > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
return true, fmt.Sprintf("lag=%fs", time.Duration(lag).Seconds())
}
checkThrottleControlReplicas := true
if (this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica) && (atomic.LoadInt64(&this.allEventsUpToLockProcessedInjectedFlag) > 0) {
checkThrottleControlReplicas = false
}
if checkThrottleControlReplicas {
lagResult := this.migrationContext.GetControlReplicasLagResult()
if lagResult.Err != nil {
return true, fmt.Sprintf("%+v %+v", lagResult.Key, lagResult.Err)
}
if lagResult.Lag > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
return true, fmt.Sprintf("%+v replica-lag=%fs", lagResult.Key, lagResult.Lag.Seconds())
}
}
// Got here? No metrics indicates we need throttling.
return false, ""
}
// readGeneralThrottleMetrics reads the once-per-sec metrics, and stores them onto this.migrationContext
func (this *Migrator) readGeneralThrottleMetrics() error {
setThrottle := func(throttle bool, reason string) error {
this.migrationContext.SetThrottleGeneralCheckResult(base.NewThrottleCheckResult(throttle, reason))
return nil
}
// Regardless of throttle, we take opportunity to check for panic-abort
if this.migrationContext.PanicFlagFile != "" {
if base.FileExists(this.migrationContext.PanicFlagFile) {
this.panicAbort <- fmt.Errorf("Found panic-file %s. Aborting without cleanup", this.migrationContext.PanicFlagFile)
}
}
criticalLoad := this.migrationContext.GetCriticalLoad()
for variableName, threshold := range criticalLoad {
value, err := this.applier.ShowStatusVariable(variableName)
if err != nil {
return setThrottle(true, fmt.Sprintf("%s %s", variableName, err))
}
if value >= threshold {
this.panicAbort <- fmt.Errorf("critical-load met: %s=%d, >=%d", variableName, value, threshold)
}
}
// Back to throttle considerations
// User-based throttle
if atomic.LoadInt64(&this.migrationContext.ThrottleCommandedByUser) > 0 {
return setThrottle(true, "commanded by user")
}
if this.migrationContext.ThrottleFlagFile != "" {
if base.FileExists(this.migrationContext.ThrottleFlagFile) {
// Throttle file defined and exists!
return setThrottle(true, "flag-file")
}
}
if this.migrationContext.ThrottleAdditionalFlagFile != "" {
if base.FileExists(this.migrationContext.ThrottleAdditionalFlagFile) {
// 2nd Throttle file defined and exists!
return setThrottle(true, "flag-file")
}
}
maxLoad := this.migrationContext.GetMaxLoad()
for variableName, threshold := range maxLoad {
value, err := this.applier.ShowStatusVariable(variableName)
if err != nil {
return setThrottle(true, fmt.Sprintf("%s %s", variableName, err))
}
if value >= threshold {
return setThrottle(true, fmt.Sprintf("max-load %s=%d >= %d", variableName, value, threshold))
}
}
if this.migrationContext.GetThrottleQuery() != "" {
if res, _ := this.applier.ExecuteThrottleQuery(); res > 0 {
return setThrottle(true, "throttle-query")
}
}
return setThrottle(false, "")
}
// initiateThrottlerMetrics initiates the various processes that collect measurements
// that may affect throttling. There are several components, all running independently,
// that collect such metrics.
func (this *Migrator) initiateThrottlerMetrics() {
go this.initiateHeartbeatReader()
go this.initiateControlReplicasReader()
go func() {
throttlerMetricsTick := time.Tick(1 * time.Second)
this.readGeneralThrottleMetrics()
this.firstThrottlingCollected <- true
for range throttlerMetricsTick {
this.readGeneralThrottleMetrics()
}
}()
}
// initiateThrottler initiates the throttle ticker and sets the basic behavior of throttling.
func (this *Migrator) initiateThrottler() error {
throttlerTick := time.Tick(100 * time.Millisecond)
throttlerFunction := func() {
alreadyThrottling, currentReason := this.migrationContext.IsThrottled()
shouldThrottle, throttleReason := this.shouldThrottle()
if shouldThrottle && !alreadyThrottling {
// New throttling
this.applier.WriteAndLogChangelog("throttle", throttleReason)
} else if shouldThrottle && alreadyThrottling && (currentReason != throttleReason) {
// Change of reason
this.applier.WriteAndLogChangelog("throttle", throttleReason)
} else if alreadyThrottling && !shouldThrottle {
// End of throttling
this.applier.WriteAndLogChangelog("throttle", "done throttling")
}
this.migrationContext.SetThrottled(shouldThrottle, throttleReason)
}
throttlerFunction()
for range throttlerTick {
throttlerFunction()
}
return nil
}
// throttle initiates a throttling event, if need be, updates the Context and
// calls callback functions, if any
func (this *Migrator) throttle(onThrottled func()) {
for {
// IsThrottled() is non-blocking; the throttling decision making takes place asynchronously.
// Therefore calling IsThrottled() is cheap
if shouldThrottle, _ := this.migrationContext.IsThrottled(); !shouldThrottle {
return
}
if onThrottled != nil {
onThrottled()
}
time.Sleep(250 * time.Millisecond)
}
}
// sleepWhileTrue sleeps indefinitely until the given function returns 'false' // sleepWhileTrue sleeps indefinitely until the given function returns 'false'
// (or fails with error) // (or fails with error)
func (this *Migrator) sleepWhileTrue(operation func() (bool, error)) error { func (this *Migrator) sleepWhileTrue(operation func() (bool, error)) error {
@ -315,7 +156,7 @@ func (this *Migrator) retryOperation(operation func() error, notFatalHint ...boo
// throttles. // throttles.
func (this *Migrator) executeAndThrottleOnError(operation func() error) (err error) { func (this *Migrator) executeAndThrottleOnError(operation func() error) (err error) {
if err := operation(); err != nil { if err := operation(); err != nil {
this.throttle(nil) this.throttler.throttle(nil)
return err return err
} }
return nil return nil
@ -373,19 +214,6 @@ func (this *Migrator) onChangelogStateEvent(dmlEvent *binlog.BinlogDMLEvent) (er
return nil return nil
} }
// parseChangelogHeartbeat is called when a heartbeat event is intercepted
func (this *Migrator) parseChangelogHeartbeat(heartbeatValue string) (err error) {
heartbeatTime, err := time.Parse(time.RFC3339Nano, heartbeatValue)
if err != nil {
return log.Errore(err)
}
lag := time.Since(heartbeatTime)
atomic.StoreInt64(&this.migrationContext.CurrentLag, int64(lag))
return nil
}
// listenOnPanicAbort aborts on abort request // listenOnPanicAbort aborts on abort request
func (this *Migrator) listenOnPanicAbort() { func (this *Migrator) listenOnPanicAbort() {
err := <-this.panicAbort err := <-this.panicAbort
@ -496,10 +324,9 @@ func (this *Migrator) Migrate() (err error) {
if err := this.applier.ReadMigrationRangeValues(); err != nil { if err := this.applier.ReadMigrationRangeValues(); err != nil {
return err return err
} }
go this.initiateThrottlerMetrics() if err := this.initiateThrottler(); err != nil {
log.Infof("Waiting for first throttle metrics to be collected") return err
<-this.firstThrottlingCollected }
go this.initiateThrottler()
if err := this.hooksExecutor.onBeforeRowCopy(); err != nil { if err := this.hooksExecutor.onBeforeRowCopy(); err != nil {
return err return err
} }
@ -547,7 +374,7 @@ func (this *Migrator) cutOver() (err error) {
return nil return nil
} }
this.migrationContext.MarkPointOfInterest() this.migrationContext.MarkPointOfInterest()
this.throttle(func() { this.throttler.throttle(func() {
log.Debugf("throttling before swapping tables") log.Debugf("throttling before swapping tables")
}) })
@ -626,7 +453,7 @@ func (this *Migrator) waitForEventsUpToLock() (err error) {
return err return err
} }
log.Infof("Waiting for events up to lock") log.Infof("Waiting for events up to lock")
atomic.StoreInt64(&this.allEventsUpToLockProcessedInjectedFlag, 1) atomic.StoreInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag, 1)
<-this.allEventsUpToLockProcessed <-this.allEventsUpToLockProcessed
waitForEventsUpToLockDuration := time.Since(waitForEventsUpToLockStartTime) waitForEventsUpToLockDuration := time.Since(waitForEventsUpToLockStartTime)
@ -643,7 +470,7 @@ func (this *Migrator) waitForEventsUpToLock() (err error) {
func (this *Migrator) cutOverTwoStep() (err error) { func (this *Migrator) cutOverTwoStep() (err error) {
atomic.StoreInt64(&this.inCutOverCriticalActionFlag, 1) atomic.StoreInt64(&this.inCutOverCriticalActionFlag, 1)
defer atomic.StoreInt64(&this.inCutOverCriticalActionFlag, 0) defer atomic.StoreInt64(&this.inCutOverCriticalActionFlag, 0)
atomic.StoreInt64(&this.allEventsUpToLockProcessedInjectedFlag, 0) atomic.StoreInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag, 0)
if err := this.retryOperation(this.applier.LockOriginalTable); err != nil { if err := this.retryOperation(this.applier.LockOriginalTable); err != nil {
return err return err
@ -674,7 +501,7 @@ func (this *Migrator) atomicCutOver() (err error) {
this.applier.DropAtomicCutOverSentryTableIfExists() this.applier.DropAtomicCutOverSentryTableIfExists()
}() }()
atomic.StoreInt64(&this.allEventsUpToLockProcessedInjectedFlag, 0) atomic.StoreInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag, 0)
lockOriginalSessionIdChan := make(chan int64, 2) lockOriginalSessionIdChan := make(chan int64, 2)
tableLocked := make(chan error, 2) tableLocked := make(chan error, 2)
@ -1142,61 +969,6 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
} }
} }
// initiateHeartbeatReader listens for heartbeat events. gh-ost implements its own
// heartbeat mechanism, whether your DB has or hasn't an existing heartbeat solution.
// Heartbeat is supplied via the changelog table
func (this *Migrator) initiateHeartbeatReader() {
ticker := time.Tick(time.Duration(this.migrationContext.HeartbeatIntervalMilliseconds) * time.Millisecond)
for range ticker {
go func() error {
if atomic.LoadInt64(&this.cleanupImminentFlag) > 0 {
return nil
}
changelogState, err := this.inspector.readChangelogState()
if err != nil {
return log.Errore(err)
}
if heartbeatValue, ok := changelogState["heartbeat"]; ok {
this.parseChangelogHeartbeat(heartbeatValue)
}
return nil
}()
}
}
// initiateControlReplicasReader
func (this *Migrator) initiateControlReplicasReader() {
readControlReplicasLag := func(replicationLagQuery string) error {
if (this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica) && (atomic.LoadInt64(&this.allEventsUpToLockProcessedInjectedFlag) > 0) {
return nil
}
lagResult := mysql.GetMaxReplicationLag(this.migrationContext.InspectorConnectionConfig, this.migrationContext.GetThrottleControlReplicaKeys(), replicationLagQuery)
this.migrationContext.SetControlReplicasLagResult(lagResult)
return nil
}
aggressiveTicker := time.Tick(100 * time.Millisecond)
relaxedFactor := 10
counter := 0
shouldReadLagAggressively := false
replicationLagQuery := ""
for range aggressiveTicker {
if counter%relaxedFactor == 0 {
// we only check if we wish to be aggressive once per second. The parameters for being aggressive
// do not typically change at all throughout the migration, but nonetheless we check them.
counter = 0
maxLagMillisecondsThrottleThreshold := atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold)
replicationLagQuery = this.migrationContext.GetReplicationLagQuery()
shouldReadLagAggressively = (replicationLagQuery != "" && maxLagMillisecondsThrottleThreshold < 1000)
}
if counter == 0 || shouldReadLagAggressively {
// We check replication lag every so often, or if we wish to be aggressive
readControlReplicasLag(replicationLagQuery)
}
counter++
}
}
// initiateStreaming begins treaming of binary log events and registers listeners for such events // initiateStreaming begins treaming of binary log events and registers listeners for such events
func (this *Migrator) initiateStreaming() error { func (this *Migrator) initiateStreaming() error {
this.eventsStreamer = NewEventsStreamer() this.eventsStreamer = NewEventsStreamer()
@ -1242,8 +1014,15 @@ func (this *Migrator) addDMLEventsListener() error {
return err return err
} }
// initiateThrottler kicks in the throttling collection and the throttling checks.
func (this *Migrator) initiateThrottler() error { func (this *Migrator) initiateThrottler() error {
this.throttler = NewThrottler(this.panicAbort) this.throttler = NewThrottler(this.applier, this.inspector, this.panicAbort)
go this.throttler.initiateThrottlerCollection(this.firstThrottlingCollected)
log.Infof("Waiting for first throttle metrics to be collected")
<-this.firstThrottlingCollected
go this.throttler.initiateThrottlerChecks()
return nil return nil
} }
@ -1338,7 +1117,7 @@ func (this *Migrator) executeWriteFuncs() error {
// - during copy phase // - during copy phase
// - just before cut-over // - just before cut-over
// - in between cut-over retries // - in between cut-over retries
this.throttle(nil) this.throttler.throttle(nil)
// When cutting over, we need to be aggressive. Cut-over holds table locks. // When cutting over, we need to be aggressive. Cut-over holds table locks.
// We need to release those asap. // We need to release those asap.
} }
@ -1384,7 +1163,7 @@ func (this *Migrator) executeWriteFuncs() error {
// finalCleanup takes actions at very end of migration, dropping tables etc. // finalCleanup takes actions at very end of migration, dropping tables etc.
func (this *Migrator) finalCleanup() error { func (this *Migrator) finalCleanup() error {
atomic.StoreInt64(&this.cleanupImminentFlag, 1) atomic.StoreInt64(&this.migrationContext.CleanupImminentFlag, 1)
if this.migrationContext.Noop { if this.migrationContext.Noop {
if createTableStatement, err := this.inspector.showCreateTable(this.migrationContext.GetGhostTableName()); err == nil { if createTableStatement, err := this.inspector.showCreateTable(this.migrationContext.GetGhostTableName()); err == nil {

256
go/logic/throttler.go Normal file
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@ -0,0 +1,256 @@
/*
Copyright 2016 GitHub Inc.
See https://github.com/github/gh-ost/blob/master/LICENSE
*/
package logic
import (
"fmt"
"sync/atomic"
"time"
"github.com/github/gh-ost/go/base"
"github.com/github/gh-ost/go/mysql"
"github.com/outbrain/golib/log"
)
// Throttler collects metrics related to throttling and makes informed decisison
// whether throttling should take place.
type Throttler struct {
migrationContext *base.MigrationContext
applier *Applier
inspector *Inspector
panicAbort chan error
}
func NewThrottler(applier *Applier, inspector *Inspector, panicAbort chan error) *Throttler {
return &Throttler{
migrationContext: base.GetMigrationContext(),
applier: applier,
inspector: inspector,
panicAbort: panicAbort,
}
}
// shouldThrottle performs checks to see whether we should currently be throttling.
// It merely observes the metrics collected by other components, it does not issue
// its own metric collection.
func (this *Throttler) shouldThrottle() (result bool, reason string) {
generalCheckResult := this.migrationContext.GetThrottleGeneralCheckResult()
if generalCheckResult.ShouldThrottle {
return generalCheckResult.ShouldThrottle, generalCheckResult.Reason
}
// Replication lag throttle
maxLagMillisecondsThrottleThreshold := atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold)
lag := atomic.LoadInt64(&this.migrationContext.CurrentLag)
if time.Duration(lag) > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
return true, fmt.Sprintf("lag=%fs", time.Duration(lag).Seconds())
}
checkThrottleControlReplicas := true
if (this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica) && (atomic.LoadInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag) > 0) {
checkThrottleControlReplicas = false
}
if checkThrottleControlReplicas {
lagResult := this.migrationContext.GetControlReplicasLagResult()
if lagResult.Err != nil {
return true, fmt.Sprintf("%+v %+v", lagResult.Key, lagResult.Err)
}
if lagResult.Lag > time.Duration(maxLagMillisecondsThrottleThreshold)*time.Millisecond {
return true, fmt.Sprintf("%+v replica-lag=%fs", lagResult.Key, lagResult.Lag.Seconds())
}
}
// Got here? No metrics indicates we need throttling.
return false, ""
}
// parseChangelogHeartbeat is called when a heartbeat event is intercepted
func (this *Throttler) parseChangelogHeartbeat(heartbeatValue string) (err error) {
heartbeatTime, err := time.Parse(time.RFC3339Nano, heartbeatValue)
if err != nil {
return log.Errore(err)
}
lag := time.Since(heartbeatTime)
atomic.StoreInt64(&this.migrationContext.CurrentLag, int64(lag))
return nil
}
// collectHeartbeat reads the latest changelog heartbeat value
func (this *Throttler) collectHeartbeat() {
ticker := time.Tick(time.Duration(this.migrationContext.HeartbeatIntervalMilliseconds) * time.Millisecond)
for range ticker {
go func() error {
if atomic.LoadInt64(&this.migrationContext.CleanupImminentFlag) > 0 {
return nil
}
changelogState, err := this.inspector.readChangelogState()
if err != nil {
return log.Errore(err)
}
if heartbeatValue, ok := changelogState["heartbeat"]; ok {
this.parseChangelogHeartbeat(heartbeatValue)
}
return nil
}()
}
}
// collectControlReplicasLag polls all the control replicas to get maximum lag value
func (this *Throttler) collectControlReplicasLag() {
readControlReplicasLag := func(replicationLagQuery string) error {
if (this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica) && (atomic.LoadInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag) > 0) {
return nil
}
lagResult := mysql.GetMaxReplicationLag(
this.migrationContext.InspectorConnectionConfig,
this.migrationContext.GetThrottleControlReplicaKeys(),
replicationLagQuery,
)
this.migrationContext.SetControlReplicasLagResult(lagResult)
return nil
}
aggressiveTicker := time.Tick(100 * time.Millisecond)
relaxedFactor := 10
counter := 0
shouldReadLagAggressively := false
replicationLagQuery := ""
for range aggressiveTicker {
if counter%relaxedFactor == 0 {
// we only check if we wish to be aggressive once per second. The parameters for being aggressive
// do not typically change at all throughout the migration, but nonetheless we check them.
counter = 0
maxLagMillisecondsThrottleThreshold := atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold)
replicationLagQuery = this.migrationContext.GetReplicationLagQuery()
shouldReadLagAggressively = (replicationLagQuery != "" && maxLagMillisecondsThrottleThreshold < 1000)
}
if counter == 0 || shouldReadLagAggressively {
// We check replication lag every so often, or if we wish to be aggressive
readControlReplicasLag(replicationLagQuery)
}
counter++
}
}
// collectGeneralThrottleMetrics reads the once-per-sec metrics, and stores them onto this.migrationContext
func (this *Throttler) collectGeneralThrottleMetrics() error {
setThrottle := func(throttle bool, reason string) error {
this.migrationContext.SetThrottleGeneralCheckResult(base.NewThrottleCheckResult(throttle, reason))
return nil
}
// Regardless of throttle, we take opportunity to check for panic-abort
if this.migrationContext.PanicFlagFile != "" {
if base.FileExists(this.migrationContext.PanicFlagFile) {
this.panicAbort <- fmt.Errorf("Found panic-file %s. Aborting without cleanup", this.migrationContext.PanicFlagFile)
}
}
criticalLoad := this.migrationContext.GetCriticalLoad()
for variableName, threshold := range criticalLoad {
value, err := this.applier.ShowStatusVariable(variableName)
if err != nil {
return setThrottle(true, fmt.Sprintf("%s %s", variableName, err))
}
if value >= threshold {
this.panicAbort <- fmt.Errorf("critical-load met: %s=%d, >=%d", variableName, value, threshold)
}
}
// Back to throttle considerations
// User-based throttle
if atomic.LoadInt64(&this.migrationContext.ThrottleCommandedByUser) > 0 {
return setThrottle(true, "commanded by user")
}
if this.migrationContext.ThrottleFlagFile != "" {
if base.FileExists(this.migrationContext.ThrottleFlagFile) {
// Throttle file defined and exists!
return setThrottle(true, "flag-file")
}
}
if this.migrationContext.ThrottleAdditionalFlagFile != "" {
if base.FileExists(this.migrationContext.ThrottleAdditionalFlagFile) {
// 2nd Throttle file defined and exists!
return setThrottle(true, "flag-file")
}
}
maxLoad := this.migrationContext.GetMaxLoad()
for variableName, threshold := range maxLoad {
value, err := this.applier.ShowStatusVariable(variableName)
if err != nil {
return setThrottle(true, fmt.Sprintf("%s %s", variableName, err))
}
if value >= threshold {
return setThrottle(true, fmt.Sprintf("max-load %s=%d >= %d", variableName, value, threshold))
}
}
if this.migrationContext.GetThrottleQuery() != "" {
if res, _ := this.applier.ExecuteThrottleQuery(); res > 0 {
return setThrottle(true, "throttle-query")
}
}
return setThrottle(false, "")
}
// initiateThrottlerMetrics initiates the various processes that collect measurements
// that may affect throttling. There are several components, all running independently,
// that collect such metrics.
func (this *Throttler) initiateThrottlerCollection(firstThrottlingCollected chan<- bool) {
go this.collectHeartbeat()
go this.collectControlReplicasLag()
go func() {
throttlerMetricsTick := time.Tick(1 * time.Second)
this.collectGeneralThrottleMetrics()
firstThrottlingCollected <- true
for range throttlerMetricsTick {
this.collectGeneralThrottleMetrics()
}
}()
}
// initiateThrottlerChecks initiates the throttle ticker and sets the basic behavior of throttling.
func (this *Throttler) initiateThrottlerChecks() error {
throttlerTick := time.Tick(100 * time.Millisecond)
throttlerFunction := func() {
alreadyThrottling, currentReason := this.migrationContext.IsThrottled()
shouldThrottle, throttleReason := this.shouldThrottle()
if shouldThrottle && !alreadyThrottling {
// New throttling
this.applier.WriteAndLogChangelog("throttle", throttleReason)
} else if shouldThrottle && alreadyThrottling && (currentReason != throttleReason) {
// Change of reason
this.applier.WriteAndLogChangelog("throttle", throttleReason)
} else if alreadyThrottling && !shouldThrottle {
// End of throttling
this.applier.WriteAndLogChangelog("throttle", "done throttling")
}
this.migrationContext.SetThrottled(shouldThrottle, throttleReason)
}
throttlerFunction()
for range throttlerTick {
throttlerFunction()
}
return nil
}
// throttle sees if throttling needs take place, and if so, continuously sleeps (blocks)
// until throttling reasons are gone
func (this *Throttler) throttle(onThrottled func()) {
for {
// IsThrottled() is non-blocking; the throttling decision making takes place asynchronously.
// Therefore calling IsThrottled() is cheap
if shouldThrottle, _ := this.migrationContext.IsThrottled(); !shouldThrottle {
return
}
if onThrottled != nil {
onThrottled()
}
time.Sleep(250 * time.Millisecond)
}
}