FindErrantGTIDs: superset is not an errant GTID situation (#16725)

Signed-off-by: deepthi <deepthi@planetscale.com>

go/mysql/replication/replication_status.go

@@ -201,6 +201,14 @@ func (s *ReplicationStatus) FindErrantGTIDs(otherReplicaStatuses []*ReplicationS
  otherSets = append(otherSets, otherSet)
  }
 
+ if len(otherSets) == 1 {
+ // If there is only one replica to compare against, and one is a subset of the other, then we consider them not to be errant.
+ // It simply means that one replica might be behind on replication.
+ if relayLogSet.Contains(otherSets[0]) || otherSets[0].Contains(relayLogSet) {
+ return nil, nil
+ }
+ }
+
  // Copy set for final diffSet so we don't mutate receiver.
  diffSet := make(Mysql56GTIDSet, len(relayLogSet))
  for sid, intervals := range relayLogSet {

go/mysql/replication/replication_status_test.go

@@ -105,6 +105,16 @@ func TestFindErrantGTIDs(t *testing.T) {
  otherRepStatuses: []*ReplicationStatus{{SourceUUID: sid1, RelayLogPosition: Position{GTIDSet: set1}}},
  // servers with the same GTID sets should not be diagnosed with errant GTIDs
  want: nil,
+ }, {
+ mainRepStatus: &ReplicationStatus{SourceUUID: sourceSID, RelayLogPosition: Position{GTIDSet: set2}},
+ otherRepStatuses: []*ReplicationStatus{{SourceUUID: sid1, RelayLogPosition: Position{GTIDSet: set3}}},
+ // set2 is a strict subset of set3
+ want: nil,
+ }, {
+ mainRepStatus: &ReplicationStatus{SourceUUID: sourceSID, RelayLogPosition: Position{GTIDSet: set3}},
+ otherRepStatuses: []*ReplicationStatus{{SourceUUID: sid1, RelayLogPosition: Position{GTIDSet: set2}}},
+ // set3 is a strict superset of set2
+ want: nil,
  }}
 
  for _, testcase := range testcases {

go/vt/vtctl/reparentutil/replication.go

@@ -123,7 +123,7 @@ func FindValidEmergencyReparentCandidates(
  case len(errantGTIDs) != 0:
  // This tablet has errant GTIDs. It's not a valid candidate for
  // reparent, so don't insert it into the final mapping.
- log.Errorf("skipping %v because we detected errant GTIDs - %v", alias, errantGTIDs)
+ log.Errorf("skipping %v with GTIDSet:%v because we detected errant GTIDs - %v", alias, relayLogGTIDSet, errantGTIDs)
  continue
  }
 

go/vt/vtctl/reparentutil/replication_test.go

@@ -161,27 +161,41 @@ func TestFindValidEmergencyReparentCandidates(t *testing.T) {
  shouldErr: false,
  },
  {
- name: "tablet with errant GTIDs is excluded",
+ name: "tablet with superset GTIDs is included",
  statusMap: map[string]*replicationdatapb.StopReplicationStatus{
  "r1": {
  After: &replicationdatapb.Status{
  SourceUuid: "3E11FA47-71CA-11E1-9E33-C80AA9429562",
  RelayLogPosition: "MySQL56/3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5",
  },
  },
- "errant": {
+ "r2": {
  After: &replicationdatapb.Status{
  SourceUuid: "3E11FA47-71CA-11E1-9E33-C80AA9429562",
  RelayLogPosition: "MySQL56/3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5,AAAAAAAA-71CA-11E1-9E33-C80AA9429562:1",
  },
  },
  },
- primaryStatusMap: map[string]*replicationdatapb.PrimaryStatus{
- "p1": {
- Position: "MySQL56/3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5",
+ expected: []string{"r1", "r2"},
+ shouldErr: false,
+ },
+ {
+ name: "tablets with errant GTIDs are excluded",
+ statusMap: map[string]*replicationdatapb.StopReplicationStatus{
+ "r1": {
+ After: &replicationdatapb.Status{
+ SourceUuid: "3E11FA47-71CA-11E1-9E33-C80AA9429562",
+ RelayLogPosition: "MySQL56/3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5,AAAAAAAA-71CA-11E1-9E33-C80AA9429562:1",
+ },
+ },
+ "r2": {
+ After: &replicationdatapb.Status{
+ SourceUuid: "3E11FA47-71CA-11E1-9E33-C80AA9429562",
+ RelayLogPosition: "MySQL56/3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5,AAAAAAAA-71CA-11E1-9E33-C80AA9429562:2-3",
+ },
  },
  },
- expected: []string{"r1", "p1"},
+ expected: []string{},
  shouldErr: false,
  },
  {