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storage: bump LastHeartbeat timestamp when writing txn record #25034

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Apr 24, 2018
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storage: bump LastHeartbeat timestamp when writing txn record #25034

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23 changes: 16 additions & 7 deletions pkg/storage/batcheval/cmd_begin_transaction.go
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,8 @@ func BeginTransaction(
clonedTxn := h.Txn.Clone()
reply.Txn = &clonedTxn

// Verify transaction does not already exist.
// Check whether the transaction record already exists. If it already
// exists, check its current status and react accordingly.
tmpTxn := roachpb.Transaction{}
ok, err := engine.MVCCGetProto(ctx, batch, key, hlc.Timestamp{}, true, nil, &tmpTxn)
if err != nil {
Expand Down Expand Up @@ -109,18 +110,26 @@ func BeginTransaction(
}
}

threshold := cArgs.EvalCtx.GetTxnSpanGCThreshold()

// Disallow creation of a transaction record if it's at a timestamp before
// the TxnSpanGCThreshold, as in that case our transaction may already have
// been aborted by a concurrent actor which encountered one of our intents
// (which may have been written before this entry).
// Disallow creation or modification of a transaction record if it's at a
// timestamp before the TxnSpanGCThreshold, as in that case our transaction
// may already have been aborted by a concurrent actor which encountered one
// of our intents (which may have been written before this entry).
//
// See #9265.
threshold := cArgs.EvalCtx.GetTxnSpanGCThreshold()
if reply.Txn.LastActive().Less(threshold) {
return result.Result{}, roachpb.NewTransactionAbortedError()
}

// Transaction heartbeats don't begin until after the transaction record
// has been laid down and the response has returned to the transaction
// coordinator. This poses a problem for BeginTxn requests that get
// delayed, because it's possible that the transaction records they
// write will look inactive immediately after being written. To avoid
// this situation resulting in transactions being aborted unnecessarily,
// we bump the record's heartbeat timestamp right before laying it down.
reply.Txn.LastHeartbeat.Forward(cArgs.EvalCtx.Clock().Now())

// Write the txn record.
reply.Txn.Writing = true
return result.Result{}, engine.MVCCPutProto(ctx, batch, cArgs.Stats, key, hlc.Timestamp{}, nil, reply.Txn)
Expand Down