// Send implements the client.Sender interface. The store is looked up from the // store map if specified by the request; otherwise, the command is being // executed locally, and the replica is determined via lookup through each // store's LookupRange method. The latter path is taken only by unit tests. func (ls *Stores) Send( ctx context.Context, ba roachpb.BatchRequest, ) (*roachpb.BatchResponse, *roachpb.Error) { // If we aren't given a Replica, then a little bending over // backwards here. This case applies exclusively to unittests. if ba.RangeID == 0 || ba.Replica.StoreID == 0 { rs, err := keys.Range(ba) if err != nil { return nil, roachpb.NewError(err) } rangeID, repDesc, err := ls.LookupReplica(rs.Key, rs.EndKey) if err != nil { return nil, roachpb.NewError(err) } ba.RangeID = rangeID ba.Replica = repDesc } store, err := ls.GetStore(ba.Replica.StoreID) if err != nil { return nil, roachpb.NewError(err) } if ba.Txn != nil { // For calls that read data within a txn, we keep track of timestamps // observed from the various participating nodes' HLC clocks. If we have // a timestamp on file for this Node which is smaller than MaxTimestamp, // we can lower MaxTimestamp accordingly. If MaxTimestamp drops below // OrigTimestamp, we effectively can't see uncertainty restarts any // more. // Note that it's not an issue if MaxTimestamp propagates back out to // the client via a returned Transaction update - when updating a Txn // from another, the larger MaxTimestamp wins. if maxTS, ok := ba.Txn.GetObservedTimestamp(ba.Replica.NodeID); ok && maxTS.Less(ba.Txn.MaxTimestamp) { // Copy-on-write to protect others we might be sharing the Txn with. shallowTxn := *ba.Txn // The uncertainty window is [OrigTimestamp, maxTS), so if that window // is empty, there won't be any uncertainty restarts. if !ba.Txn.OrigTimestamp.Less(maxTS) { log.Event(ctx, "read has no clock uncertainty") } shallowTxn.MaxTimestamp.Backward(maxTS) ba.Txn = &shallowTxn } } br, pErr := store.Send(ctx, ba) if br != nil && br.Error != nil { panic(roachpb.ErrorUnexpectedlySet(store, br)) } return br, pErr }