co.cask.tephra

Class TransactionContext

java.lang.Object

co.cask.tephra.TransactionContext

public class TransactionContext
extends Object

Utility class that encapsulates the transaction life cycle over a given set of transaction-aware datasets. It is not thread-safe for concurrent execution.

Constructor Summary

Constructors

Constructor and Description
TransactionContext(TransactionSystemClient txClient, Iterable<TransactionAware> txAwares)
TransactionContext(TransactionSystemClient txClient, TransactionAware... txAwares)

Method Summary

Methods

Modifier and Type	Method and Description
void	abort() Aborts the given transaction, and rolls back all data set changes.
void	abort(TransactionFailureException cause) Aborts the given transaction, and rolls back all data set changes.
void	addTransactionAware(TransactionAware txAware) Adds a new transaction-aware to participate in the transaction.
void	checkpoint() Checkpoints the current transaction by flushing any pending writes for the registered TransactionAware instances, and obtaining a new current write pointer for the transaction.
void	finish() Commits the current transaction.
Transaction	getCurrentTransaction() Returns the current transaction or null if no transaction is currently in progress.
void	start() Starts a new transaction.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TransactionContext

public TransactionContext(TransactionSystemClient txClient,
                  TransactionAware... txAwares)

TransactionContext

public TransactionContext(TransactionSystemClient txClient,
                  Iterable<TransactionAware> txAwares)

Method Detail

addTransactionAware

public void addTransactionAware(TransactionAware txAware)

Adds a new transaction-aware to participate in the transaction.

Parameters:

txAware - the new transaction-aware

start

public void start()
           throws TransactionFailureException

Starts a new transaction. Calling this will initiate a new transaction using the TransactionSystemClient, and pass the returned transaction to TransactionAware.startTx(Transaction) for each registered TransactionAware. If an exception is encountered, the transaction will be aborted and a TransactionFailureException wrapping the root cause will be thrown.

Throws:

TransactionFailureException - if an exception occurs starting the transaction with any registered TransactionAware

finish

public void finish()
            throws TransactionFailureException

Commits the current transaction. This will: check for any conflicts, based on the change set aggregated from all registered TransactionAware instances; flush any pending writes from the TransactionAwares; commit the current transaction with the TransactionSystemClient; and clear the current transaction state.

Throws:

TransactionConflictException - if a conflict is detected with a recently committed transaction

TransactionFailureException - if an error occurs while committing

abort

public void abort()
           throws TransactionFailureException

Aborts the given transaction, and rolls back all data set changes. If rollback fails, the transaction is invalidated. If an exception is caught during rollback, the exception is rethrown wrapped in a TransactionFailureException, after all remaining TransactionAwares have completed rollback.

Throws:

TransactionFailureException - for any exception that is encountered.

checkpoint

public void checkpoint()
                throws TransactionFailureException

Checkpoints the current transaction by flushing any pending writes for the registered TransactionAware instances, and obtaining a new current write pointer for the transaction. By performing a checkpoint, the client can ensure that all previous writes were flushed and are visible. By default, the current write pointer for the transaction is also visible. The current write pointer can be excluded from read operations by setting an attribute with the key TxConstants#TX_EXCLUDE_CURRENT_WRITE on the Get or Scan operation. After the checkpoint operation is performed, the updated Transaction instance will be passed to TransactionAware.startTx(Transaction) for each registered TransactionAware instance.

Throws:

TransactionFailureException - if an error occurs while performing the checkpoint

getCurrentTransaction

@Nullable
public Transaction getCurrentTransaction()

Returns the current transaction or null if no transaction is currently in progress.

abort

public void abort(TransactionFailureException cause)
           throws TransactionFailureException

Aborts the given transaction, and rolls back all data set changes. If rollback fails, the transaction is invalidated. If an exception is caught during rollback, the exception is rethrown wrapped into a TransactionFailureException, after all remaining TransactionAwares have completed rollback. If an existing exception is passed in, that exception is thrown in either case, whether the rollback is successful or not. In other words, this method always throws the first exception that it encounters.

Parameters:

cause - the original exception that caused the abort

Throws:

TransactionFailureException - for any exception that is encountered.