// getTablets gets all available tablets from HealthCheck,
// and selects the usable ones based several rules:
// master - return one from any cells with latest reparent timestamp;
// replica - return all from local cell.
func (dg *discoveryGateway) getTablets(keyspace, shard string, tabletType topodatapb.TabletType) []*discovery.TabletStats {
tsList := dg.hc.GetTabletStatsFromTarget(keyspace, shard, tabletType)
// for master, use any cells and return the one with max reparent timestamp.
if tabletType == topodatapb.TabletType_MASTER {
var maxTimestamp int64
var t *discovery.TabletStats
for _, ts := range tsList {
if ts.LastError != nil || !ts.Serving {
continue
}
if ts.TabletExternallyReparentedTimestamp >= maxTimestamp {
maxTimestamp = ts.TabletExternallyReparentedTimestamp
t = ts
}
}
if t == nil {
return nil
}
return []*discovery.TabletStats{t}
}
// for non-master, use only tablets from local cell and filter by replication lag.
list := make([]*discovery.TabletStats, 0, len(tsList))
for _, ts := range tsList {
if ts.LastError != nil || !ts.Serving {
continue
}
if dg.localCell != ts.Tablet.Alias.Cell {
continue
}
list = append(list, ts)
}
list = discovery.FilterByReplicationLag(list)
return list
}
// getEndPoints gets all available endpoints from HealthCheck,
// and selects the usable ones based several rules:
// master - return one from any cells with latest reparent timestamp;
// replica - return all from local cell.
// TODO(liang): select replica by replication lag.
func (dg *discoveryGateway) getEndPoints(keyspace, shard string, tabletType pbt.TabletType) []*pbt.EndPoint {
epsList := dg.hc.GetEndPointStatsFromTarget(keyspace, shard, tabletType)
// for master, use any cells and return the one with max reparent timestamp.
if tabletType == pbt.TabletType_MASTER {
var maxTimestamp int64
var ep *pbt.EndPoint
for _, eps := range epsList {
if eps.LastError != nil || !eps.Serving {
continue
}
if eps.TabletExternallyReparentedTimestamp >= maxTimestamp {
maxTimestamp = eps.TabletExternallyReparentedTimestamp
ep = eps.EndPoint
}
}
if ep == nil {
return nil
}
return []*pbt.EndPoint{ep}
}
// for non-master, use only endpoints from local cell and filter by replication lag.
list := make([]*discovery.EndPointStats, 0, len(epsList))
for _, eps := range epsList {
if eps.LastError != nil || !eps.Serving {
continue
}
if dg.localCell != eps.Cell {
continue
}
list = append(list, eps)
}
list = discovery.FilterByReplicationLag(list)
epList := make([]*pbt.EndPoint, 0, len(list))
for _, eps := range list {
epList = append(epList, eps.EndPoint)
}
return epList
}