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Online DDL: resume vreplication after cut-over/RENAME failure #18428

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Merged
shlomi-noach merged 5 commits into from
Jul 10, 2025
Merged

Online DDL: resume vreplication after cut-over/RENAME failure #18428

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474fb29
Online DDL: resume vreplication after cut-over/RENAME failure
shlomi-noach Jul 8, 2025
67de091
ensure to remvoe vreplication entry when starting a vrepl migration (…
shlomi-noach Jul 8, 2025
b180f6f
typo
shlomi-noach Jul 8, 2025
b337478
Update go/vt/vttablet/onlineddl/executor.go
shlomi-noach Jul 10, 2025
bffd76f
fix referencing call
shlomi-noach Jul 10, 2025
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2 changes: 1 addition & 1 deletion go/test/endtoend/onlineddl/scheduler/onlineddl_scheduler_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1352,7 +1352,7 @@ func testScheduler(t *testing.T) {
onlineddl.CheckMigrationStatus(t, &vtParams, shards, uuid, schema.OnlineDDLStatusCancelled)
})

// now, we submit the exact same migratoin again: same UUID, same migration context.
// now, we submit the exact same migration again: same UUID, same migration context.
t.Run("resubmit migration", func(t *testing.T) {
executedUUID := testOnlineDDLStatement(t, createParams(trivialAlterT1Statement, ddlStrategy, "vtctl", "", "", true)) // skip wait
require.Equal(t, uuid, executedUUID)
Expand Down
37 changes: 32 additions & 5 deletions go/vt/vttablet/onlineddl/executor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -605,7 +605,7 @@ func (e *Executor) primaryPosition(ctx context.Context) (pos replication.Positio
}

// terminateVReplMigration stops vreplication, then removes the _vt.vreplication entry for the given migration
func (e *Executor) terminateVReplMigration(ctx context.Context, uuid string) error {
func (e *Executor) terminateVReplMigration(ctx context.Context, uuid string, deleteEntry bool) error {
tablet, err := e.ts.GetTablet(ctx, e.tabletAlias)
if err != nil {
return err
Expand All @@ -621,10 +621,26 @@ func (e *Executor) terminateVReplMigration(ctx context.Context, uuid string) err
if _, err := e.vreplicationExec(ctx, tablet.Tablet, query); err != nil {
log.Errorf("FAIL vreplicationExec: uuid=%s, query=%v, error=%v", uuid, query, err)
}
if deleteEntry {
if err := e.deleteVReplicationEntry(ctx, uuid); err != nil {
return err
}
}

if err := e.deleteVReplicationEntry(ctx, uuid); err != nil {
return nil
}

func (e *Executor) startVReplication(ctx context.Context, tablet *topodatapb.Tablet, workflow string) (err error) {
query, err := sqlparser.ParseAndBind(sqlStartVReplStream,
sqltypes.StringBindVariable(e.dbName),
sqltypes.StringBindVariable(workflow),
)
if err != nil {
return err
}
if _, err := e.vreplicationExec(ctx, tablet, query); err != nil {
return vterrors.Wrapf(err, "FAIL vreplicationExec: uuid=%s, query=%v", workflow, query)
}
return nil
}

Expand Down Expand Up @@ -1071,6 +1087,16 @@ func (e *Executor) cutOverVReplMigration(ctx context.Context, s *VReplStream, sh
}
go log.Infof("cutOverVReplMigration %v: stopped vreplication", s.workflow)

defer func() {
if !renameWasSuccessful {
// Restarting vreplication
if err := e.startVReplication(ctx, tablet.Tablet, s.workflow); err != nil {
log.Errorf("cutOverVReplMigration %v: failed restarting vreplication after cutover failure: %v", s.workflow, err)
}
go log.Infof("cutOverVReplMigration %v: started vreplication after cutover failure", s.workflow)
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@harshit-gangal harshit-gangal Jul 9, 2025

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why to start a goroutine for calling in log function?

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@shlomi-noach shlomi-noach Jul 9, 2025

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because in this critical section I don't want to block on writing a log line, as silly as it may be.

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@dbussink dbussink Jul 10, 2025

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@shlomi-noach Is it then essential to log at all? Starting a goroutine also has some cost 😄.

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@shlomi-noach shlomi-noach Jul 10, 2025

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@dbussink , yeah, I'd like this entry to appear in the logs. If it appears, it means vreplication has definitely started, which is an important info

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@shlomi-noach shlomi-noach Jul 10, 2025

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This will not be the only go log.Infof call in the cutOverVReplMigration function. There's a bunch of other such calls.

}
}()

// rename tables atomically (remember, writes on source tables are stopped)
{
if isVreplicationTestSuite {
Expand Down Expand Up @@ -1345,7 +1371,7 @@ func (e *Executor) initVreplicationRevertMigration(ctx context.Context, onlineDD
// ExecuteWithVReplication sets up the grounds for a vreplication schema migration
func (e *Executor) ExecuteWithVReplication(ctx context.Context, onlineDDL *schema.OnlineDDL, revertMigration *schema.OnlineDDL) error {
// make sure there's no vreplication workflow running under same name
_ = e.terminateVReplMigration(ctx, onlineDDL.UUID)
_ = e.terminateVReplMigration(ctx, onlineDDL.UUID, true)

if e.tabletTypeFunc() != topodatapb.TabletType_PRIMARY {
return ErrExecutorNotWritableTablet
Expand Down Expand Up @@ -1506,7 +1532,7 @@ func (e *Executor) terminateMigration(ctx context.Context, onlineDDL *schema.Onl
// migration could have started by a different tablet. We need to actively verify if it is running
s, _ := e.readVReplStream(ctx, onlineDDL.UUID, true)
foundRunning = (s != nil && s.isRunning())
if err := e.terminateVReplMigration(ctx, onlineDDL.UUID); err != nil {
if err := e.terminateVReplMigration(ctx, onlineDDL.UUID, false); err != nil {
return foundRunning, fmt.Errorf("Error terminating migration, vreplication exec error: %+v", err)
}
}
Expand Down Expand Up @@ -3137,6 +3163,7 @@ func (e *Executor) reviewRunningMigrations(ctx context.Context) (countRunnning i
cancellable = append(cancellable, newCancellableMigration(uuid, s.message))
}
if !s.isRunning() {
log.Infof("migration %s in 'running' state but vreplication state is '%s'", uuid, s.state.String())
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@shlomi-noach shlomi-noach Jul 8, 2025

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Just some added visibility.

return nil
}
// This VRepl migration may have started from outside this tablet, so
Expand Down Expand Up @@ -4128,7 +4155,7 @@ func (e *Executor) ForceCutOverPendingMigrations(ctx context.Context) (result *s
if err != nil {
return result, err
}
log.Infof("ForceCutOverPendingMigrations: iterating %v migrations %s", len(uuids))
log.Infof("ForceCutOverPendingMigrations: iterating %v migrations", len(uuids))

result = &sqltypes.Result{}
for _, uuid := range uuids {
Expand Down
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