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ddl_worker.go
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ddl_worker.go
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// Copyright 2015 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package ddl
import (
"time"
"github.com/juju/errors"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/meta"
"github.com/pingcap/tidb/metrics"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/binloginfo"
"github.com/pingcap/tidb/terror"
"github.com/pingcap/tidb/util"
log "github.com/sirupsen/logrus"
"golang.org/x/net/context"
)
// RunWorker indicates if this TiDB server starts DDL worker and can run DDL job.
var RunWorker = true
// onDDLWorker is for async online schema changing, it will try to become the owner firstly,
// then wait or pull the job queue to handle a schema change job.
func (d *ddl) onDDLWorker() {
defer d.wait.Done()
// We use 4 * lease time to check owner's timeout, so here, we will update owner's status
// every 2 * lease time. If lease is 0, we will use default 1s.
// But we use etcd to speed up, normally it takes less than 1s now, so we use 1s as the max value.
checkTime := chooseLeaseTime(2*d.lease, 1*time.Second)
ticker := time.NewTicker(checkTime)
defer ticker.Stop()
defer func() {
r := recover()
if r != nil {
buf := util.GetStack()
log.Errorf("ddlWorker %v %s", r, buf)
metrics.PanicCounter.WithLabelValues(metrics.LabelDDL).Inc()
}
}()
// shouldCleanJobs is used to determine whether to clean up the job in adding index queue.
shouldCleanJobs := true
for {
select {
case <-ticker.C:
log.Debugf("[ddl] wait %s to check DDL status again", checkTime)
case <-d.ddlJobCh:
case <-d.quitCh:
return
}
err := d.handleDDLJobQueue(shouldCleanJobs)
if err != nil {
log.Errorf("[ddl] handle ddl job err %v", errors.ErrorStack(err))
} else if shouldCleanJobs {
log.Info("[ddl] cleaning jobs in the adding index queue finished.")
shouldCleanJobs = false
}
}
}
func asyncNotify(ch chan struct{}) {
select {
case ch <- struct{}{}:
default:
}
}
func cleanNotify(ch chan struct{}) {
select {
case <-ch:
default:
}
}
func (d *ddl) isOwner() bool {
isOwner := d.ownerManager.IsOwner()
log.Debugf("[ddl] it's the job owner %v, self id %s", isOwner, d.uuid)
if isOwner {
metrics.DDLCounter.WithLabelValues(metrics.IsDDLOwner).Inc()
}
return isOwner
}
// buildJobDependence sets the curjob's dependency-ID.
// The dependency-job's ID must less than the current job's ID, and we need the largest one in the list.
func buildJobDependence(t *meta.Meta, curJob *model.Job) error {
jobs, err := t.GetAllDDLJobs()
if err != nil {
return errors.Trace(err)
}
for _, job := range jobs {
if curJob.ID < job.ID {
continue
}
isDependent, err := curJob.IsDependentOn(job)
if err != nil {
return errors.Trace(err)
}
if isDependent {
curJob.DependencyID = job.ID
break
}
}
return nil
}
// addDDLJob gets a global job ID and puts the DDL job in the DDL queue.
func (d *ddl) addDDLJob(ctx sessionctx.Context, job *model.Job) error {
startTime := time.Now()
job.Version = currentVersion
job.Query, _ = ctx.Value(sessionctx.QueryString).(string)
err := kv.RunInNewTxn(d.store, true, func(txn kv.Transaction) error {
t := meta.NewMeta(txn)
var err error
job.ID, err = t.GenGlobalID()
if err != nil {
return errors.Trace(err)
}
job.StartTS = txn.StartTS()
err = t.EnQueueDDLJob(job)
return errors.Trace(err)
})
metrics.DDLWorkerHistogram.WithLabelValues(metrics.WorkerAddDDLJob, metrics.RetLabel(err)).Observe(time.Since(startTime).Seconds())
return errors.Trace(err)
}
// getFirstDDLJob gets the first DDL job form DDL queue.
func (d *ddl) getFirstDDLJob(t *meta.Meta) (*model.Job, error) {
job, err := t.GetDDLJob(0)
return job, errors.Trace(err)
}
// handleUpdateJobError handles the too large DDL job.
func (d *ddl) handleUpdateJobError(t *meta.Meta, job *model.Job, err error) error {
if err == nil {
return nil
}
if kv.ErrEntryTooLarge.Equal(err) {
log.Warnf("[ddl] update DDL job %v failed %v", job, errors.ErrorStack(err))
// Reduce this txn entry size.
job.BinlogInfo.Clean()
job.Error = toTError(err)
job.SchemaState = model.StateNone
job.State = model.JobStateCancelled
err = d.finishDDLJob(t, job)
}
return errors.Trace(err)
}
// updateDDLJob updates the DDL job information.
// Every time we enter another state except final state, we must call this function.
func (d *ddl) updateDDLJob(t *meta.Meta, job *model.Job, meetErr bool) error {
updateRawArgs := true
// If there is an error when running job and the RawArgs hasn't been decoded by DecodeArgs,
// so we shouldn't replace RawArgs with the marshaling Args.
if meetErr && (job.RawArgs != nil && job.Args == nil) {
log.Infof("[ddl] update DDL Job %s shouldn't update raw args", job)
updateRawArgs = false
}
return errors.Trace(t.UpdateDDLJob(0, job, updateRawArgs))
}
func (d *ddl) deleteRange(job *model.Job) error {
var err error
if job.Version <= currentVersion {
err = d.delRangeManager.addDelRangeJob(job)
} else {
err = errInvalidJobVersion.GenByArgs(job.Version, currentVersion)
}
return errors.Trace(err)
}
// finishDDLJob deletes the finished DDL job in the ddl queue and puts it to history queue.
// If the DDL job need to handle in background, it will prepare a background job.
func (d *ddl) finishDDLJob(t *meta.Meta, job *model.Job) (err error) {
startTime := time.Now()
defer func() {
metrics.DDLWorkerHistogram.WithLabelValues(metrics.WorkerFinishDDLJob, metrics.RetLabel(err)).Observe(time.Since(startTime).Seconds())
}()
switch job.Type {
case model.ActionAddIndex:
if job.State != model.JobStateRollbackDone {
break
}
// After rolling back an AddIndex operation, we need to use delete-range to delete the half-done index data.
err = d.deleteRange(job)
case model.ActionDropSchema, model.ActionDropTable, model.ActionTruncateTable, model.ActionDropIndex:
err = d.deleteRange(job)
}
if err != nil {
return errors.Trace(err)
}
_, err = t.DeQueueDDLJob()
if err != nil {
return errors.Trace(err)
}
job.BinlogInfo.FinishedTS = t.StartTS
log.Infof("[ddl] finish DDL job %v", job)
err = t.AddHistoryDDLJob(job)
return errors.Trace(err)
}
// getHistoryDDLJob gets a DDL job with job's ID form history queue.
func (d *ddl) getHistoryDDLJob(id int64) (*model.Job, error) {
var job *model.Job
err := kv.RunInNewTxn(d.store, false, func(txn kv.Transaction) error {
t := meta.NewMeta(txn)
var err1 error
job, err1 = t.GetHistoryDDLJob(id)
return errors.Trace(err1)
})
return job, errors.Trace(err)
}
// handleDDLJobQueue handles DDL jobs in DDL Job queue.
// shouldCleanJobs is used to determine whether to clean up the job in adding index queue.
func (d *ddl) handleDDLJobQueue(shouldCleanJobs bool) error {
once := true
for {
if d.isClosed() {
return nil
}
waitTime := 2 * d.lease
var (
job *model.Job
schemaVer int64
runJobErr error
)
err := kv.RunInNewTxn(d.store, false, func(txn kv.Transaction) error {
// We are not owner, return and retry checking later.
if !d.isOwner() {
return nil
}
// It's used for clean up the job in adding index queue before we support adding index queue.
// TODO: Remove this logic after we support the adding index queue.
if shouldCleanJobs {
return errors.Trace(d.cleanAddIndexQueueJobs(txn))
}
var err error
t := meta.NewMeta(txn)
// We become the owner. Get the first job and run it.
job, err = d.getFirstDDLJob(t)
if job == nil || err != nil {
return errors.Trace(err)
}
if once {
d.waitSchemaSynced(job, waitTime)
once = false
return nil
}
if job.IsDone() || job.IsRollbackDone() {
binloginfo.SetDDLBinlog(d.workerVars.BinlogClient, txn, job.ID, job.Query)
if !job.IsRollbackDone() {
job.State = model.JobStateSynced
}
err = d.finishDDLJob(t, job)
return errors.Trace(err)
}
d.hookMu.Lock()
d.hook.OnJobRunBefore(job)
d.hookMu.Unlock()
// If running job meets error, we will save this error in job Error
// and retry later if the job is not cancelled.
schemaVer, runJobErr = d.runDDLJob(t, job)
if job.IsCancelled() {
err = d.finishDDLJob(t, job)
return errors.Trace(err)
}
err = d.updateDDLJob(t, job, runJobErr != nil)
return errors.Trace(d.handleUpdateJobError(t, job, err))
})
if runJobErr != nil {
// wait a while to retry again. If we don't wait here, DDL will retry this job immediately,
// which may act like a deadlock.
log.Infof("[ddl] run DDL job error, sleep a while:%v then retry it.", waitTimeWhenErrorOccured)
metrics.DDLJobErrCounter.Inc()
time.Sleep(waitTimeWhenErrorOccured)
}
if err != nil {
return errors.Trace(err)
} else if job == nil {
// No job now, return and retry getting later.
return nil
}
d.hookMu.Lock()
d.hook.OnJobUpdated(job)
d.hookMu.Unlock()
// Here means the job enters another state (delete only, write only, public, etc...) or is cancelled.
// If the job is done or still running or rolling back, we will wait 2 * lease time to guarantee other servers to update
// the newest schema.
if job.IsRunning() || job.IsRollingback() || job.IsDone() || job.IsRollbackDone() {
d.waitSchemaChanged(nil, waitTime, schemaVer)
}
if job.IsSynced() {
asyncNotify(d.ddlJobDoneCh)
}
}
}
func chooseLeaseTime(t, max time.Duration) time.Duration {
if t == 0 || t > max {
return max
}
return t
}
// runDDLJob runs a DDL job. It returns the current schema version in this transaction and the error.
func (d *ddl) runDDLJob(t *meta.Meta, job *model.Job) (ver int64, err error) {
log.Infof("[ddl] run DDL job %s", job)
if job.IsFinished() {
return
}
// The cause of this job state is that the job is cancelled by client.
if job.IsCancelling() {
// If the value of SnapshotVer isn't zero, it means the work is backfilling the indexes.
if job.Type == model.ActionAddIndex && job.SchemaState == model.StateWriteReorganization && job.SnapshotVer != 0 {
log.Infof("[ddl] run the cancelling DDL job %s", job)
d.reorgCtx.notifyReorgCancel()
} else {
job.State = model.JobStateCancelled
job.Error = errCancelledDDLJob
job.ErrorCount++
return
}
}
if !job.IsRollingback() && !job.IsCancelling() {
job.State = model.JobStateRunning
}
switch job.Type {
case model.ActionCreateSchema:
ver, err = d.onCreateSchema(t, job)
case model.ActionDropSchema:
ver, err = d.onDropSchema(t, job)
case model.ActionCreateTable:
ver, err = d.onCreateTable(t, job)
case model.ActionDropTable:
ver, err = d.onDropTable(t, job)
case model.ActionAddColumn:
ver, err = d.onAddColumn(t, job)
case model.ActionDropColumn:
ver, err = d.onDropColumn(t, job)
case model.ActionModifyColumn:
ver, err = d.onModifyColumn(t, job)
case model.ActionAddIndex:
ver, err = d.onCreateIndex(t, job)
case model.ActionDropIndex:
ver, err = d.onDropIndex(t, job)
case model.ActionAddForeignKey:
ver, err = d.onCreateForeignKey(t, job)
case model.ActionDropForeignKey:
ver, err = d.onDropForeignKey(t, job)
case model.ActionTruncateTable:
ver, err = d.onTruncateTable(t, job)
case model.ActionRebaseAutoID:
ver, err = d.onRebaseAutoID(t, job)
case model.ActionRenameTable:
ver, err = d.onRenameTable(t, job)
case model.ActionSetDefaultValue:
ver, err = d.onSetDefaultValue(t, job)
case model.ActionShardRowID:
ver, err = d.onShardRowID(t, job)
case model.ActionModifyTableComment:
ver, err = d.onModifyTableComment(t, job)
default:
// Invalid job, cancel it.
job.State = model.JobStateCancelled
err = errInvalidDDLJob.Gen("invalid ddl job %v", job)
}
// Save errors in job, so that others can know errors happened.
if err != nil {
// If job is not cancelled, we should log this error.
if job.State != model.JobStateCancelled {
log.Errorf("[ddl] run DDL job err %v", errors.ErrorStack(err))
} else {
log.Infof("[ddl] the DDL job is normal to cancel because %v", errors.ErrorStack(err))
}
job.Error = toTError(err)
job.ErrorCount++
}
return
}
func toTError(err error) *terror.Error {
originErr := errors.Cause(err)
tErr, ok := originErr.(*terror.Error)
if ok {
return tErr
}
// TODO: Add the error code.
return terror.ClassDDL.New(terror.CodeUnknown, err.Error())
}
// waitSchemaChanged waits for the completion of updating all servers' schema. In order to make sure that happens,
// we wait 2 * lease time.
func (d *ddl) waitSchemaChanged(ctx context.Context, waitTime time.Duration, latestSchemaVersion int64) {
if waitTime == 0 {
return
}
timeStart := time.Now()
var err error
defer func() {
metrics.DDLWorkerHistogram.WithLabelValues(metrics.WorkerWaitSchemaChanged, metrics.RetLabel(err)).Observe(time.Since(timeStart).Seconds())
}()
if latestSchemaVersion == 0 {
log.Infof("[ddl] schema version doesn't change")
return
}
if ctx == nil {
var cancelFunc context.CancelFunc
ctx, cancelFunc = context.WithTimeout(context.Background(), waitTime)
defer cancelFunc()
}
err = d.schemaSyncer.OwnerUpdateGlobalVersion(ctx, latestSchemaVersion)
if err != nil {
log.Infof("[ddl] update latest schema version %d failed %v", latestSchemaVersion, err)
if terror.ErrorEqual(err, context.DeadlineExceeded) {
// If err is context.DeadlineExceeded, it means waitTime(2 * lease) is elapsed. So all the schemas are synced by ticker.
// There is no need to use etcd to sync. The function returns directly.
return
}
}
// OwnerCheckAllVersions returns only when context is timeout(2 * lease) or all TiDB schemas are synced.
err = d.schemaSyncer.OwnerCheckAllVersions(ctx, latestSchemaVersion)
if err != nil {
log.Infof("[ddl] wait latest schema version %d to deadline %v", latestSchemaVersion, err)
if terror.ErrorEqual(err, context.DeadlineExceeded) {
return
}
select {
case <-ctx.Done():
return
}
}
log.Infof("[ddl] wait latest schema version %v changed, take time %v", latestSchemaVersion, time.Since(timeStart))
return
}
// waitSchemaSynced handles the following situation:
// If the job enters a new state, and the worker crashs when it's in the process of waiting for 2 * lease time,
// Then the worker restarts quickly, we may run the job immediately again,
// but in this case we don't wait enough 2 * lease time to let other servers update the schema.
// So here we get the latest schema version to make sure all servers' schema version update to the latest schema version
// in a cluster, or to wait for 2 * lease time.
func (d *ddl) waitSchemaSynced(job *model.Job, waitTime time.Duration) {
if !job.IsRunning() && !job.IsRollingback() && !job.IsDone() && !job.IsRollbackDone() {
return
}
// TODO: Make ctx exits when the d is close.
ctx, cancelFunc := context.WithTimeout(context.Background(), waitTime)
defer cancelFunc()
startTime := time.Now()
latestSchemaVersion, err := d.schemaSyncer.MustGetGlobalVersion(ctx)
if err != nil {
log.Warnf("[ddl] handle exception take time %v", time.Since(startTime))
return
}
d.waitSchemaChanged(ctx, waitTime, latestSchemaVersion)
log.Infof("[ddl] the handle exception take time %v", time.Since(startTime))
}
// updateSchemaVersion increments the schema version by 1 and sets SchemaDiff.
func updateSchemaVersion(t *meta.Meta, job *model.Job) (int64, error) {
schemaVersion, err := t.GenSchemaVersion()
if err != nil {
return 0, errors.Trace(err)
}
diff := &model.SchemaDiff{
Version: schemaVersion,
Type: job.Type,
SchemaID: job.SchemaID,
}
if job.Type == model.ActionTruncateTable {
// Truncate table has two table ID, should be handled differently.
err = job.DecodeArgs(&diff.TableID)
if err != nil {
return 0, errors.Trace(err)
}
diff.OldTableID = job.TableID
} else if job.Type == model.ActionRenameTable {
err = job.DecodeArgs(&diff.OldSchemaID)
if err != nil {
return 0, errors.Trace(err)
}
diff.TableID = job.TableID
} else {
diff.TableID = job.TableID
}
err = t.SetSchemaDiff(diff)
return schemaVersion, errors.Trace(err)
}
// cleanAddIndexQueueJobs cleans jobs in adding index queue.
// It's only done once after the worker become the owner.
// TODO: Remove this logic after we support the adding index queue.
func (d *ddl) cleanAddIndexQueueJobs(txn kv.Transaction) error {
startTime := time.Now()
m := meta.NewMeta(txn)
m.SetJobListKey(meta.AddIndexJobListKey)
for {
job, err := d.getFirstDDLJob(m)
if err != nil {
return errors.Trace(err)
}
if job == nil {
log.Infof("[ddl] cleaning jobs in the adding index queue takes time %v.", time.Since(startTime))
return nil
}
log.Infof("[ddl] cleaning job %v in the adding index queue.", job)
// The types of these jobs must be ActionAddIndex.
if job.SchemaState == model.StatePublic || job.SchemaState == model.StateNone {
if job.SchemaState == model.StateNone {
job.State = model.JobStateCancelled
} else {
binloginfo.SetDDLBinlog(d.workerVars.BinlogClient, txn, job.ID, job.Query)
job.State = model.JobStateSynced
}
err = d.finishDDLJob(m, job)
if err != nil {
return errors.Trace(err)
}
continue
}
// When the job not in "none" and "public" state, we need to rollback it.
schemaID := job.SchemaID
tblInfo, err := getTableInfo(m, job, schemaID)
if err != nil {
return errors.Trace(err)
}
var indexName model.CIStr
var unique bool
err = job.DecodeArgs(&unique, &indexName)
if err != nil {
return errors.Trace(err)
}
indexInfo := findIndexByName(indexName.L, tblInfo.Indices)
_, err = d.convert2RollbackJob(m, job, tblInfo, indexInfo, nil)
if err == nil {
_, err = m.DeQueueDDLJob()
}
if err != nil {
return errors.Trace(err)
}
// Put the job to the default job list.
m.SetJobListKey(meta.DefaultJobListKey)
err = m.EnQueueDDLJob(job)
m.SetJobListKey(meta.AddIndexJobListKey)
if err != nil {
return errors.Trace(err)
}
}
}