[release-21.0] [Direct PR] Add RPC to read the reparent journal posit…

…ion (#16982)

Signed-off-by: Manan Gupta <[email protected]>

go/test/endtoend/tabletmanager/replication_manager/tablet_test.go

@@ -205,3 +205,13 @@ func TestReplicationRepairAfterPrimaryTabletChange(t *testing.T) {
 	// sidecardb should find the desired _vt schema and not apply any new creates or upgrades when the tablet comes up again
 	require.Equal(t, sidecarDDLCount, int64(0))
 }
+
+func TestReparentJournalInfo(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	for _, vttablet := range clusterInstance.Keyspaces[0].Shards[0].Vttablets {
+		length, err := tmClient.ReadReparentJournalInfo(ctx, getTablet(vttablet.GrpcPort))
+		require.NoError(t, err)
+		require.EqualValues(t, 1, length)
+	}
+}

go/vt/mysqlctl/reparent.go

@@ -22,6 +22,7 @@ This file contains the reparenting methods for mysqlctl.
 
 import (
 	"context"
+	"fmt"
 	"time"
 
 	"vitess.io/vitess/go/constants/sidecar"
@@ -53,6 +54,11 @@ func PopulateReparentJournal(timeCreatedNS int64, actionName, primaryAlias strin
 		timeCreatedNS, actionName, primaryAlias, posStr).Query
 }
 
+// ReadReparentJournalInfoQuery returns the query we use to read information required from Reparent Journal.
+func ReadReparentJournalInfoQuery() string {
+	return fmt.Sprintf("SELECT COUNT(*) FROM %s.reparent_journal", sidecar.GetIdentifier())
+}
+
 // queryReparentJournal returns the SQL query to use to query the database
 // for a reparent_journal row.
 func queryReparentJournal(timeCreatedNS int64) string {