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at resurrection, pointing streamer back at last known applied coordinates

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This commit is contained in:
Shlomi Noach 2016-12-24 09:53:55 +02:00
parent 1080b11d81
commit e50361ab61
2 changed files with 47 additions and 27 deletions
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47
go/logic/migrator.go
View File

@ -31,7 +31,7 @@ const (
AllEventsUpToLockProcessed = "AllEventsUpToLockProcessed"
)
const contextDumpInterval time.Duration = 1 * time.Second
const contextDumpInterval time.Duration = 1 * time.Minute
func ReadChangelogState(s string) ChangelogState {
return ChangelogState(strings.Split(s, ":")[0])
@ -63,6 +63,7 @@ type Migrator struct {
throttler *Throttler
hooksExecutor *HooksExecutor
migrationContext *base.MigrationContext
resurrectedContext *base.MigrationContext
firstThrottlingCollected chan bool
ghostTableMigrated chan bool
@ -272,7 +273,7 @@ func (this *Migrator) countTableRows() (err error) {
return countRowsFunc()
}
func (this *Migrator) resurrect() error {
func (this *Migrator) readResurrectedContext() error {
encodedContext, err := this.inspector.readChangelogState("context")
if err != nil {
return err
@ -280,25 +281,30 @@ func (this *Migrator) resurrect() error {
if encodedContext == "" {
return fmt.Errorf("No resurrect info found")
}
log.Infof("Proceeding to resurrection")
// Loading migration context to a temporary location:
loadedContext := base.NewMigrationContext()
if err := loadedContext.LoadJSON(encodedContext); err != nil {
this.resurrectedContext = base.NewMigrationContext()
if err := this.resurrectedContext.LoadJSON(encodedContext); err != nil {
return err
}
// Sanity: heuristically verify loaded context truly reflects our very own context (e.g. is this the same migration on the same table?)
if this.migrationContext.DatabaseName != loadedContext.DatabaseName {
if this.migrationContext.DatabaseName != this.resurrectedContext.DatabaseName {
return fmt.Errorf("Resurrection: given --database not identical to resurrected one. Bailing out")
}
if this.migrationContext.OriginalTableName != loadedContext.OriginalTableName {
if this.migrationContext.OriginalTableName != this.resurrectedContext.OriginalTableName {
return fmt.Errorf("Resurrection: given --table not identical to resurrected one. Bailing out")
}
if this.migrationContext.AlterStatement != loadedContext.AlterStatement {
if this.migrationContext.AlterStatement != this.resurrectedContext.AlterStatement {
return fmt.Errorf("Resurrection: given --alter statement not identical to resurrected one. Bailing out")
}
// Happy. Let's go live and update our real context
this.migrationContext.ApplyResurrectedContext(loadedContext)
if this.resurrectedContext.AppliedBinlogCoordinates.IsEmpty() {
return fmt.Errorf("Resurrection: no applied binlog coordinates. Seems like the migration you're trying to resurrect crashed before applying a single binlog event. There's not enough info for resurrection, and not much point to it. Just run your migration again.")
}
return nil
}
func (this *Migrator) applyResurrectedContext() error {
this.migrationContext.ApplyResurrectedContext(this.resurrectedContext)
return nil
}
@ -328,6 +334,11 @@ func (this *Migrator) Migrate() (err error) {
if err := this.initiateInspector(); err != nil {
return err
}
if this.migrationContext.Resurrect {
if err := this.readResurrectedContext(); err != nil {
return err
}
}
if err := this.initiateStreaming(); err != nil {
return err
}
@ -372,7 +383,7 @@ func (this *Migrator) Migrate() (err error) {
return err
}
if this.migrationContext.Resurrect {
if err := this.resurrect(); err != nil {
if err := this.applyResurrectedContext(); err != nil {
return err
}
}
@ -929,15 +940,19 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
// initiateStreaming begins treaming of binary log events and registers listeners for such events
func (this *Migrator) initiateStreaming() error {
this.eventsStreamer = NewEventsStreamer()
if err := this.eventsStreamer.InitDBConnections(); err != nil {
if err := this.eventsStreamer.InitDBConnections(this.resurrectedContext); err != nil {
return err
}
this.eventsStreamer.AddListener(
false,
this.migrationContext.DatabaseName,
this.migrationContext.GetChangelogTableName(),
func(dmlEvent *binlog.BinlogDMLEvent, _ *mysql.BinlogCoordinates) error {
return this.onChangelogStateEvent(dmlEvent)
func(dmlEvent *binlog.BinlogDMLEvent, coordinates *mysql.BinlogCoordinates) error {
err := this.onChangelogStateEvent(dmlEvent)
if err == nil {
this.migrationContext.SetAppliedBinlogCoordinates(coordinates)
}
return err
},
)
@ -963,7 +978,7 @@ func (this *Migrator) addDMLEventsListener() error {
// Create a task to apply the DML event; this will be execute by executeWriteFuncs()
applyEventFunc := func() error {
err := this.applier.ApplyDMLEventQuery(dmlEvent)
if err != nil {
if err == nil {
this.migrationContext.SetAppliedBinlogCoordinates(coordinates)
}
return err
@ -1091,7 +1106,7 @@ func (this *Migrator) executeWriteFuncs() error {
if !this.migrationContext.Resurrect || this.migrationContext.IsResurrected {
if jsonString, err := this.migrationContext.ToJSON(); err == nil {
this.applier.WriteChangelog("context", jsonString)
log.Debugf("Context dumped")
log.Debugf("Context dumped. Applied coordinates: %+v", this.migrationContext.AppliedBinlogCoordinates)
}
}
// If we're about to resurrect (resurrect requested) but haven't done so yet, do not wrtie resurrect info.

7
go/logic/streamer.go
View File

@ -105,7 +105,7 @@ func (this *EventsStreamer) notifyListeners(binlogEntry *binlog.BinlogEntry) {
}
}
func (this *EventsStreamer) InitDBConnections() (err error) {
func (this *EventsStreamer) InitDBConnections(resurrectedContext *base.MigrationContext) (err error) {
EventsStreamerUri := this.connectionConfig.GetDBUri(this.migrationContext.DatabaseName)
if this.db, _, err = sqlutils.GetDB(EventsStreamerUri); err != nil {
return err
@ -113,9 +113,14 @@ func (this *EventsStreamer) InitDBConnections() (err error) {
if err := this.validateConnection(); err != nil {
return err
}
if this.migrationContext.Resurrect {
log.Infof("Resurrection: initiating streamer at resurrected coordinates %+v", resurrectedContext.AppliedBinlogCoordinates)
this.initialBinlogCoordinates = &resurrectedContext.AppliedBinlogCoordinates
} else {
if err := this.readCurrentBinlogCoordinates(); err != nil {
return err
}
}
if err := this.initBinlogReader(this.initialBinlogCoordinates); err != nil {
return err
}