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
}