Golang Transaction.Update方法代碼示例

// 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,
	startNS int64,
	ba roachpb.BatchRequest,
	br *roachpb.BatchResponse,
	pErr *roachpb.Error,
) *roachpb.Error {

	tc.Lock()
	defer tc.Unlock()

	if ba.Txn == nil {
		// Not a transactional request.
		return pErr
	}

	var newTxn roachpb.Transaction
	newTxn.Update(ba.Txn)
	if pErr == nil {
		newTxn.Update(br.Txn)
	} else if errTxn := pErr.GetTxn(); errTxn != nil {
		newTxn.Update(errTxn)
	}

	switch t := pErr.GetDetail().(type) {
	case *roachpb.OpRequiresTxnError:
		panic("OpRequiresTxnError must not happen at this level")
	case *roachpb.ReadWithinUncertaintyIntervalError:
		// If the reader encountered a newer write within the uncertainty
		// interval, we advance the txn's timestamp just past the last observed
		// timestamp from the node.
		restartTS, ok := newTxn.GetObservedTimestamp(pErr.OriginNode)
		if !ok {
			pErr = roachpb.NewError(errors.Errorf("no observed timestamp for node %d found on uncertainty restart", pErr.OriginNode))
		} else {
			newTxn.Timestamp.Forward(restartTS)
			newTxn.Restart(ba.UserPriority, newTxn.Priority, newTxn.Timestamp)
		}
	case *roachpb.TransactionAbortedError:
		// Increase timestamp if applicable.
		newTxn.Timestamp.Forward(pErr.GetTxn().Timestamp)
		newTxn.Priority = pErr.GetTxn().Priority
		// Clean up the freshly aborted transaction in defer(), avoiding a
		// race with the state update below.
		defer tc.cleanupTxnLocked(ctx, newTxn)
	case *roachpb.TransactionPushError:
		// Increase timestamp if applicable, ensuring that we're
		// just ahead of the pushee.
		newTxn.Timestamp.Forward(t.PusheeTxn.Timestamp)
		newTxn.Restart(ba.UserPriority, t.PusheeTxn.Priority-1, newTxn.Timestamp)
	case *roachpb.TransactionRetryError:
		// Increase timestamp so on restart, we're ahead of any timestamp
		// cache entries or newer versions which caused the restart.
		newTxn.Restart(ba.UserPriority, pErr.GetTxn().Priority, newTxn.Timestamp)
	case *roachpb.WriteTooOldError:
		newTxn.Restart(ba.UserPriority, newTxn.Priority, t.ActualTimestamp)
	case nil:
		// Nothing to do here, avoid the default case.
	default:
		// Do not clean up the transaction since we're leaving cancellation of
		// the transaction up to the client. For example, on seeing an error,
		// like TransactionStatusError or ConditionFailedError, the client
		// will call Txn.CleanupOnError() which will cleanup the transaction
		// and its intents. Therefore leave the transaction in the PENDING
		// state and do not call cleanTxnLocked().
	}

	txnID := *newTxn.ID

	txnMeta := tc.txns[txnID]
	// 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.
	// A tricky edge case is that of a transaction which "fails" on the
	// first writing request, but actually manages to write some intents
	// (for example, due to being multi-range). In this case, there will
	// be an error, but the transaction will be marked as Writing and the
	// coordinator must track the state, for the client's retry will be
	// performed with a Writing transaction which the coordinator rejects
	// unless it is tracking it (on top of it making sense to track it;
	// after all, it **has** laid down intents and only the coordinator
	// can augment a potential EndTransaction call). See #3303.
	if txnMeta != nil || pErr == nil || newTxn.Writing {
		// Adding the intents even on error reduces the likelihood of dangling
		// intents blocking concurrent writers for extended periods of time.
		// See #3346.
		var keys []roachpb.Span
		if txnMeta != nil {
			keys = txnMeta.keys
		}
		ba.IntentSpanIterate(br, func(key, endKey roachpb.Key) {
			keys = append(keys, roachpb.Span{
				Key:    key,
				EndKey: endKey,
			})
		})
//.........這裏部分代碼省略.........