// SendBatch implements the batch.Sender interface. It subdivides
// the Batch into batches admissible for sending (preventing certain
// illegal mixtures of requests), executes each individual part
// (which may span multiple ranges), and recombines the response.
func (ds *DistSender) SendBatch(ctx context.Context, ba proto.BatchRequest) (*proto.BatchResponse, error) {
// In the event that timestamp isn't set and read consistency isn't
// required, set the timestamp using the local clock.
// TODO(tschottdorf): right place for this?
if ba.ReadConsistency == proto.INCONSISTENT && ba.Timestamp.Equal(proto.ZeroTimestamp) {
// Make sure that after the call, args hasn't changed.
defer func(timestamp proto.Timestamp) {
ba.Timestamp = timestamp
}(ba.Timestamp)
ba.Timestamp = ds.clock.Now()
}
// TODO(tschottdorf): provisional instantiation.
return newChunkingSender(ds.sendChunk).SendBatch(ctx, ba)
}
func testPut() proto.BatchRequest {
var ba proto.BatchRequest
ba.Timestamp = testTS
put := &proto.PutRequest{}
put.Key = testKey
ba.Add(put)
return ba
}
func (tc *TxnCoordSender) heartbeat(id string, trace *tracer.Trace, ctx context.Context) bool {
tc.Lock()
proceed := true
txnMeta := tc.txns[id]
// Before we send a heartbeat, determine whether this transaction
// should be considered abandoned. If so, exit heartbeat.
if txnMeta.hasClientAbandonedCoord(tc.clock.PhysicalNow()) {
// TODO(tschottdorf): should we be more proactive here?
// The client might be continuing the transaction
// through another coordinator, but in the most likely
// case it's just gone and the open transaction record
// could block concurrent operations.
if log.V(1) {
log.Infof("transaction %s abandoned; stopping heartbeat",
txnMeta.txn)
}
proceed = false
}
// txnMeta.txn is possibly replaced concurrently,
// so grab a copy before unlocking.
txn := txnMeta.txn
tc.Unlock()
if !proceed {
return false
}
hb := &proto.HeartbeatTxnRequest{}
hb.Key = txn.Key
ba := proto.BatchRequest{}
ba.Timestamp = tc.clock.Now()
ba.Key = txn.Key
ba.Txn = &txn
ba.Add(hb)
epochEnds := trace.Epoch("heartbeat")
_, err := tc.wrapped.Send(ctx, ba)
epochEnds()
// If the transaction is not in pending state, then we can stop
// the heartbeat. It's either aborted or committed, and we resolve
// write intents accordingly.
if err != nil {
log.Warningf("heartbeat to %s failed: %s", txn, err)
}
// TODO(bdarnell): once we have gotten a heartbeat response with
// Status != PENDING, future heartbeats are useless. However, we
// need to continue the heartbeatLoop until the client either
// commits or abandons the transaction. We could save a little
// pointless work by restructuring this loop to stop sending
// heartbeats between the time that the transaction is aborted and
// the client finds out. Furthermore, we could use this information
// to send TransactionAbortedErrors to the client so it can restart
// immediately instead of running until its EndTransaction.
return true
}
// Send implements the batch.Sender interface. If the request is part of a
// transaction, the TxnCoordSender adds the transaction to a map of active
// transactions and begins heartbeating it. Every subsequent request for the
// same transaction updates the lastUpdate timestamp to prevent live
// transactions from being considered abandoned and garbage collected.
// Read/write mutating requests have their key or key range added to the
// transaction's interval tree of key ranges for eventual cleanup via resolved
// write intents; they're tagged to an outgoing EndTransaction request, with
// the receiving replica in charge of resolving them.
func (tc *TxnCoordSender) Send(ctx context.Context, ba proto.BatchRequest) (*proto.BatchResponse, *proto.Error) {
tc.maybeBeginTxn(&ba)
ba.CmdID = ba.GetOrCreateCmdID(tc.clock.PhysicalNow())
var startNS int64
// This is the earliest point at which the request has a ClientCmdID and/or
// TxnID (if applicable). Begin a Trace which follows this request.
trace := tc.tracer.NewTrace(&ba)
defer trace.Finalize()
// TODO(tschottdorf): always "Batch"
defer trace.Epoch(fmt.Sprintf("sending %s", ba.Method()))()
ctx = tracer.ToCtx(ctx, trace)
// TODO(tschottdorf): No looping through the batch will be necessary once
// we've eliminated all the redundancies.
for _, arg := range ba.Requests {
trace.Event(fmt.Sprintf("%T", arg.GetValue()))
if err := updateForBatch(arg.GetInner(), ba.RequestHeader); err != nil {
return nil, proto.NewError(err)
}
}
var id string // optional transaction ID
if ba.Txn != nil {
// If this request is part of a transaction...
id = string(ba.Txn.ID)
// Verify that if this Transaction is not read-only, we have it on
// file. If not, refuse writes - the client must have issued a write on
// another coordinator previously.
if ba.Txn.Writing && ba.IsTransactionWrite() {
tc.Lock()
_, ok := tc.txns[id]
tc.Unlock()
if !ok {
return nil, proto.NewError(util.Errorf("transaction must not write on multiple coordinators"))
}
}
// Set the timestamp to the original timestamp for read-only
// commands and to the transaction timestamp for read/write
// commands.
if ba.IsReadOnly() {
ba.Timestamp = ba.Txn.OrigTimestamp
} else {
ba.Timestamp = ba.Txn.Timestamp
}
if rArgs, ok := ba.GetArg(proto.EndTransaction); ok {
et := rArgs.(*proto.EndTransactionRequest)
// Remember when EndTransaction started in case we want to
// be linearizable.
startNS = tc.clock.PhysicalNow()
if len(et.Intents) > 0 {
// TODO(tschottdorf): it may be useful to allow this later.
// That would be part of a possible plan to allow txns which
// write on multiple coordinators.
return nil, proto.NewError(util.Errorf("client must not pass intents to EndTransaction"))
}
if len(et.Key) != 0 {
return nil, proto.NewError(util.Errorf("EndTransaction must not have a Key set"))
}
et.Key = ba.Txn.Key
tc.Lock()
txnMeta, metaOK := tc.txns[id]
if id != "" && metaOK {
et.Intents = txnMeta.intents()
}
tc.Unlock()
if intents := ba.GetIntents(); len(intents) > 0 {
// Writes in Batch, so EndTransaction is fine. Should add
// outstanding intents to EndTransaction, though.
// TODO(tschottdorf): possible issues when the batch fails,
// but the intents have been added anyways.
// TODO(tschottdorf): some of these intents may be covered
// by others, for example {[a,b), a}). This can lead to
// some extra requests when those are non-local to the txn
// record. But it doesn't seem worth optimizing now.
et.Intents = append(et.Intents, intents...)
} else if !metaOK {
// If we don't have the transaction, then this must be a retry
// by the client. We can no longer reconstruct a correct
// request so we must fail.
//
// TODO(bdarnell): if we had a GetTransactionStatus API then
// we could lookup the transaction and return either nil or
// TransactionAbortedError instead of this ambivalent error.
return nil, proto.NewError(util.Errorf("transaction is already committed or aborted"))
}
if len(et.Intents) == 0 {
// If there aren't any intents, then there's factually no
// transaction to end. Read-only txns have all of their state in
// the client.
return nil, proto.NewError(util.Errorf("cannot commit a read-only transaction"))
}
// TODO(tschottdorf): V(1)
for _, intent := range et.Intents {
trace.Event(fmt.Sprintf("intent: [%s,%s)", intent.Key, intent.EndKey))
}
}
}
// Send the command through wrapped sender, taking appropriate measures
// on error.
var br *proto.BatchResponse
{
var pErr *proto.Error
br, pErr = tc.wrapped.Send(ctx, ba)
if _, ok := pErr.GoError().(*proto.OpRequiresTxnError); ok {
br, pErr = tc.resendWithTxn(ba)
}
if pErr := tc.updateState(ctx, ba, br, pErr); pErr != nil {
return nil, pErr
}
}
if br.Txn == nil {
return br, nil
}
if _, ok := ba.GetArg(proto.EndTransaction); !ok {
return br, nil
}
// If the --linearizable flag is set, we want to make sure that
// all the clocks in the system are past the commit timestamp
// of the transaction. This is guaranteed if either
// - the commit timestamp is MaxOffset behind startNS
// - MaxOffset ns were spent in this function
// when returning to the client. Below we choose the option
// that involves less waiting, which is likely the first one
// unless a transaction commits with an odd timestamp.
if tsNS := br.Txn.Timestamp.WallTime; startNS > tsNS {
startNS = tsNS
}
sleepNS := tc.clock.MaxOffset() -
time.Duration(tc.clock.PhysicalNow()-startNS)
if tc.linearizable && sleepNS > 0 {
defer func() {
if log.V(1) {
log.Infof("%v: waiting %s on EndTransaction for linearizability", br.Txn.Short(), util.TruncateDuration(sleepNS, time.Millisecond))
}
time.Sleep(sleepNS)
}()
}
if br.Txn.Status != proto.PENDING {
tc.cleanupTxn(trace, *br.Txn)
}
return br, nil
}