// 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 roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
if err := tc.maybeBeginTxn(&ba); err != nil {
return nil, roachpb.NewError(err)
}
var startNS int64
ba.SetNewRequest()
// This is the earliest point at which the request has an ID (if
// applicable). Begin a Trace which follows this request.
sp := tc.tracer.StartTrace(ba.TraceID())
defer sp.Finish()
sp.LogEvent("sending batch")
ctx, _ = opentracing.ContextWithSpan(ctx, sp)
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, roachpb.NewErrorf("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(roachpb.EndTransaction); ok {
et := rArgs.(*roachpb.EndTransactionRequest)
if len(et.Key) != 0 {
return nil, roachpb.NewErrorf("EndTransaction must not have a Key set")
}
et.Key = ba.Txn.Key
// Remember when EndTransaction started in case we want to
// be linearizable.
startNS = tc.clock.PhysicalNow()
if len(et.IntentSpans) > 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, roachpb.NewErrorf("client must not pass intents to EndTransaction")
}
tc.Lock()
txnMeta, metaOK := tc.txns[id]
if id != "" && metaOK {
et.IntentSpans = txnMeta.intentSpans()
}
tc.Unlock()
if intentSpans := ba.GetIntentSpans(); len(intentSpans) > 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.IntentSpans = append(et.IntentSpans, intentSpans...)
} 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, roachpb.NewErrorf("transaction is already committed or aborted")
}
if len(et.IntentSpans) == 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, roachpb.NewErrorf("cannot commit a read-only transaction")
}
if log.V(1) {
for _, intent := range et.IntentSpans {
sp.LogEvent(fmt.Sprintf("intent: [%s,%s)", intent.Key, intent.EndKey))
}
}
}
}
// Send the command through wrapped sender, taking appropriate measures
// on error.
var br *roachpb.BatchResponse
{
var pErr *roachpb.Error
br, pErr = tc.wrapped.Send(ctx, ba)
if _, ok := pErr.GetDetail().(*roachpb.OpRequiresTxnError); ok {
br, pErr = tc.resendWithTxn(ba)
}
if pErr = tc.updateState(ctx, ba, br, pErr); pErr != nil {
sp.LogEvent(fmt.Sprintf("error: %s", pErr))
return nil, pErr
}
}
if br.Txn == nil {
return br, nil
}
if _, ok := ba.GetArg(roachpb.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 != roachpb.PENDING {
tc.cleanupTxn(sp, *br.Txn)
}
return br, nil
}