// updateState updates the transaction state in both the success and
// error cases, applying those updates to the corresponding txnMeta
// object when adequate. It also updates certain errors with the
// updated transaction for use by client restarts.
func (tc *TxnCoordSender) updateState(ctx context.Context, ba proto.BatchRequest, br *proto.BatchResponse, pErr *proto.Error) *proto.Error {
trace := tracer.FromCtx(ctx)
newTxn := &proto.Transaction{}
newTxn.Update(ba.GetTxn())
err := pErr.GoError()
switch t := err.(type) {
case nil:
newTxn.Update(br.GetTxn())
// Move txn timestamp forward to response timestamp if applicable.
// TODO(tschottdorf): see (*Replica).executeBatch and comments within.
// Looks like this isn't necessary any more, nor did it prevent a bug
// referenced in a TODO there.
newTxn.Timestamp.Forward(br.Timestamp)
case *proto.TransactionStatusError:
// Likely already committed or more obscure errors such as epoch or
// timestamp regressions; consider txn dead.
defer tc.cleanupTxn(trace, t.Txn)
case *proto.OpRequiresTxnError:
// TODO(tschottdorf): range-spanning autowrap currently broken.
panic("TODO(tschottdorf): disabled")
case *proto.ReadWithinUncertaintyIntervalError:
// Mark the host as certain. See the protobuf comment for
// Transaction.CertainNodes for details.
if t.NodeID == 0 {
panic("no replica set in header on uncertainty restart")
}
newTxn.CertainNodes.Add(t.NodeID)
// If the reader encountered a newer write within the uncertainty
// interval, move the timestamp forward, just past that write or
// up to MaxTimestamp, whichever comes first.
candidateTS := newTxn.MaxTimestamp
candidateTS.Backward(t.ExistingTimestamp.Add(0, 1))
newTxn.Timestamp.Forward(candidateTS)
newTxn.Restart(ba.GetUserPriority(), newTxn.Priority, newTxn.Timestamp)
t.Txn = *newTxn
case *proto.TransactionAbortedError:
// Increase timestamp if applicable.
newTxn.Timestamp.Forward(t.Txn.Timestamp)
newTxn.Priority = t.Txn.Priority
t.Txn = *newTxn
// Clean up the freshly aborted transaction in defer(), avoiding a
// race with the state update below.
defer tc.cleanupTxn(trace, t.Txn)
case *proto.TransactionPushError:
// Increase timestamp if applicable, ensuring that we're
// just ahead of the pushee.
newTxn.Timestamp.Forward(t.PusheeTxn.Timestamp.Add(0, 1))
newTxn.Restart(ba.GetUserPriority(), t.PusheeTxn.Priority-1, newTxn.Timestamp)
t.Txn = newTxn
case *proto.TransactionRetryError:
// Increase timestamp if applicable.
newTxn.Timestamp.Forward(t.Txn.Timestamp)
newTxn.Restart(ba.GetUserPriority(), t.Txn.Priority, newTxn.Timestamp)
t.Txn = *newTxn
case proto.TransactionRestartError:
// Assertion: The above cases should exhaust all ErrorDetails which
// carry a Transaction.
if pErr.Detail != nil {
panic(fmt.Sprintf("unhandled TransactionRestartError %T", err))
}
}
return func() *proto.Error {
if len(newTxn.ID) <= 0 {
return pErr
}
id := string(newTxn.ID)
tc.Lock()
defer tc.Unlock()
txnMeta := tc.txns[id]
// For successful transactional requests, keep the written intents and
// the updated transaction record to be sent along with the reply.
// The transaction metadata is created with the first writing operation
// TODO(tschottdorf): already computed the intents prior to sending,
// consider re-using those.
if intents := ba.GetIntents(); len(intents) > 0 && err == nil {
if txnMeta == nil {
newTxn.Writing = true
txnMeta = &txnMetadata{
txn: *newTxn,
keys: cache.NewIntervalCache(cache.Config{Policy: cache.CacheNone}),
firstUpdateNanos: tc.clock.PhysicalNow(),
lastUpdateNanos: tc.clock.PhysicalNow(),
timeoutDuration: tc.clientTimeout,
txnEnd: make(chan struct{}),
}
tc.txns[id] = txnMeta
// If the transaction is already over, there's no point in
// launching a one-off coordinator which will shut down right
// away.
if _, isEnding := ba.GetArg(proto.EndTransaction); !isEnding {
trace.Event("coordinator spawns")
if !tc.stopper.RunAsyncTask(func() {
tc.heartbeatLoop(id)
}) {
// The system is already draining and we can't start the
// heartbeat. We refuse new transactions for now because
// they're likely not going to have all intents committed.
// In principle, we can relax this as needed though.
tc.unregisterTxnLocked(id)
return proto.NewError(&proto.NodeUnavailableError{})
}
}
}
for _, intent := range intents {
txnMeta.addKeyRange(intent.Key, intent.EndKey)
}
}
// Update our record of this transaction, even on error.
if txnMeta != nil {
txnMeta.txn.Update(newTxn) // better to replace after #2300
if !txnMeta.txn.Writing {
panic("tracking a non-writing txn")
}
txnMeta.setLastUpdate(tc.clock.PhysicalNow())
}
if err == nil {
// For successful transactional requests, always send the updated txn
// record back.
if br.Txn == nil {
br.Txn = &proto.Transaction{}
}
*br.Txn = *newTxn
}
return pErr
}()
}
// 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
}