Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

SwitchTraffic: use separate context while canceling a migration #17340

Merged
merged 3 commits into from
Dec 10, 2024
Merged

SwitchTraffic: use separate context while canceling a migration #17340

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
d499bc3
Use fresh context while canceling a migration
rohit-nayak-ps Dec 5, 2024
f54bf63
Simplify comment
rohit-nayak-ps Dec 9, 2024
1ab5b14
Address review comments
rohit-nayak-ps Dec 10, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
27 changes: 21 additions & 6 deletions go/vt/vtctl/workflow/traffic_switcher.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1135,30 +1135,45 @@ func (ts *trafficSwitcher) switchDeniedTables(ctx context.Context) error {
return nil
}

// cancelMigration attempts to revert all changes made during the migration so that we can get back to the
// state when traffic switching (or reversing) was initiated.
func (ts *trafficSwitcher) cancelMigration(ctx context.Context, sm *StreamMigrator) {
var err error

if ctx.Err() != nil {
// Even though we create a new context later on we still record any context error:
// for forensics in case of failures.
ts.Logger().Infof("In Cancel migration: original context invalid: %s", ctx.Err())
}

// We create a new context while canceling the migration, so that we are independent of the original
// context being cancelled prior to or during the cancel operation.
cmTimeout := 60 * time.Second
cmCtx, cmCancel := context.WithTimeout(context.Background(), cmTimeout)
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It probably does not matter logically, but I'm often wondering whether semantically context.WithoutCancel would be more accurate in this situation?

Suggested change
cmCtx, cmCancel := context.WithTimeout(context.Background(), cmTimeout)
cmCtx, cmCancel := context.WithTimeout(context.WithoutCancel(ctx), cmTimeout)

It probably makes no difference as we're not using values stored on the context.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It is possible that we get here when the ctx is already cancelled. In the specific case which lead us to this issue the client had a short timeout and original context's deadline had already expired.

defer cmCancel()

if ts.MigrationType() == binlogdatapb.MigrationType_TABLES {
err = ts.switchDeniedTables(ctx)
err = ts.switchDeniedTables(cmCtx)
} else {
err = ts.changeShardsAccess(ctx, ts.SourceKeyspaceName(), ts.SourceShards(), allowWrites)
err = ts.changeShardsAccess(cmCtx, ts.SourceKeyspaceName(), ts.SourceShards(), allowWrites)
}
if err != nil {
ts.Logger().Errorf("Cancel migration failed: %v", err)
ts.Logger().Errorf("Cancel migration failed: could not revert denied tables / shard access: %v", err)
}

sm.CancelStreamMigrations(ctx)
sm.CancelStreamMigrations(cmCtx)

err = ts.ForAllTargets(func(target *MigrationTarget) error {
query := fmt.Sprintf("update _vt.vreplication set state='Running', message='' where db_name=%s and workflow=%s",
encodeString(target.GetPrimary().DbName()), encodeString(ts.WorkflowName()))
_, err := ts.TabletManagerClient().VReplicationExec(ctx, target.GetPrimary().Tablet, query)
_, err := ts.TabletManagerClient().VReplicationExec(cmCtx, target.GetPrimary().Tablet, query)
return err
})
if err != nil {
ts.Logger().Errorf("Cancel migration failed: could not restart vreplication: %v", err)
}

err = ts.deleteReverseVReplication(ctx)
err = ts.deleteReverseVReplication(cmCtx)
if err != nil {
ts.Logger().Errorf("Cancel migration failed: could not delete reverse vreplication streams: %v", err)
}
Expand Down
Loading