// 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
}