Package org.apache.ignite.transactions

Interface Transaction

  • All Superinterfaces:
    AutoCloseable, IgniteAsyncSupport
    public interface Transaction
extends AutoCloseable, IgniteAsyncSupport
    Ignite cache transaction. Cache transactions have a default 2PC (two-phase-commit) behavior and can be plugged into ongoing JTA transaction by properly implementing CacheTmLookup interface. Cache transactions can also be started explicitly directly from IgniteTransactions API via any of the 'IgniteTransactions.txStart(..)' methods.

    Cache transactions support the following isolation levels:

    • TransactionIsolation.READ_COMMITTED isolation level means that always a committed value will be provided for read operations. With this isolation level values are always read from cache global memory or persistent store every time a value is accessed. In other words, if the same key is accessed more than once within the same transaction, it may have different value every time since global cache memory may be updated concurrently by other threads.
    • TransactionIsolation.REPEATABLE_READ isolation level means that if a value was read once within transaction, then all consecutive reads will provide the same in-transaction value. With this isolation level accessed values are stored within in-transaction memory, so consecutive access to the same key within the same transaction will always return the value that was previously read or updated within this transaction. If concurrency is TransactionConcurrency.PESSIMISTIC, then a lock on the key will be acquired prior to accessing the value.
    • TransactionIsolation.SERIALIZABLE isolation level means that all transactions occur in a completely isolated fashion, as if all transactions in the system had executed serially, one after the other. Read access with this level happens the same way as with TransactionIsolation.REPEATABLE_READ level. However, in TransactionConcurrency.OPTIMISTIC mode, if some transactions cannot be serially isolated from each other, then one winner will be picked and the other transactions in conflict will result in TransactionOptimisticException being thrown.

    Cache transactions support the following concurrency models:

    • TransactionConcurrency.OPTIMISTIC - in this mode all cache operations are not distributed to other nodes until commit() is called. In this mode one 'PREPARE' message will be sent to participating cache nodes to start acquiring per-transaction locks, and once all nodes reply 'OK' (i.e. Phase 1 completes successfully), a one-way' 'COMMIT' message is sent without waiting for reply. If it is necessary to know whenever remote nodes have committed as well, synchronous commit or synchronous rollback should be enabled via CacheConfiguration.setWriteSynchronizationMode(org.apache.ignite.cache.CacheWriteSynchronizationMode).

      Note that in this mode, optimistic failures are only possible in conjunction with TransactionIsolation.SERIALIZABLE isolation level. In all other cases, optimistic transactions will never fail optimistically and will always be identically ordered on all participating grid nodes.

    • TransactionConcurrency.PESSIMISTIC - in this mode a lock is acquired on all cache operations with exception of read operations in TransactionIsolation.READ_COMMITTED mode. All optional filters passed into cache operations will be evaluated after successful lock acquisition. Whenever commit() is called, a single one-way 'COMMIT' message is sent to participating cache nodes without waiting for reply. Note that there is no reason for distributed 'PREPARE' step, as all locks have been already acquired. Just like with optimistic mode, it is possible to configure synchronous commit or rollback and wait till transaction commits on all participating remote nodes.

    Cache Atomicity Mode

    In addition to standard CacheAtomicityMode.TRANSACTIONAL behavior, Ignite also supports a lighter CacheAtomicityMode.ATOMIC mode as well. In this mode distributed transactions and distributed locking are not supported. Disabling transactions and locking allows to achieve much higher performance and throughput ratios. It is recommended that CacheAtomicityMode.ATOMIC mode is used whenever full ACID-compliant transactions are not needed.

    Usage

    You can use cache transactions as follows: 
     Ignite ignite = Ignition.ignite();

 IgniteCache<String, Integer> cache = ignite.cache(cacheName);

 try (Transaction tx = ignite.transactions().txStart()) {
     // Perform transactional operations.
     Integer v1 = cache.get("k1");

     // Check if v1 satisfies some condition before doing a put.
     if (v1 != null && v1 > 0)
         cache.put("k1", 2);

     cache.remove("k2");

     // Commit the transaction.
     tx.commit();
 }

    • Method Detail

      • xid

        IgniteUuid xid()
        Gets unique identifier for this transaction.
        Returns:
        Transaction UID.

      • nodeId

        UUID nodeId()
        ID of the node on which this transaction started.
        Returns:
        Originating node ID.

      • threadId

        long threadId()
        ID of the thread in which this transaction started.
        Returns:
        Thread ID.

      • startTime

        long startTime()
        Start time of this transaction.
        Returns:
        Start time of this transaction on this node.

      • isolation

        TransactionIsolation isolation()
        Cache transaction isolation level.
        Returns:
        Isolation level.

      • concurrency

        TransactionConcurrency concurrency()
        Cache transaction concurrency mode.
        Returns:
        Concurrency mode.

      • implicit

        boolean implicit()
        Flag indicating whether transaction was started automatically by the system or not. System will start transactions implicitly whenever any cache put(..) or remove(..) operation is invoked outside of transaction.
        Returns:
        True if transaction was started implicitly.

      • isInvalidate

        boolean isInvalidate()
        Get invalidation flag for this transaction. If set to true, then remote values will be invalidated (set to null) instead of updated.

        Invalidation messages don't carry new values, so they are a lot lighter than update messages. However, when a value is accessed on a node after it's been invalidated, it must be loaded from persistent store.

        Returns:
        Invalidation flag.

      • state

        TransactionState state()
        Gets current transaction state value.
        Returns:
        Current transaction state.

      • timeout

        long timeout()
        Gets timeout value in milliseconds for this transaction. If transaction times out prior to it's completion, TransactionTimeoutException will be thrown.
        Returns:
        Transaction timeout value.

      • timeout

        long timeout​(long timeout)
        Sets transaction timeout value. This value can be set only before a first operation on transaction has been performed.
        Parameters:
        timeout - Transaction timeout value.
        Returns:
        Previous timeout.

      • setRollbackOnly

        boolean setRollbackOnly()
        Modify the transaction associated with the current thread such that the only possible outcome of the transaction is to roll back the transaction.
        Returns:
        True if rollback-only flag was set as a result of this operation, false if it was already set prior to this call or could not be set because transaction is already finishing up committing or rolling back.

      • isRollbackOnly

        boolean isRollbackOnly()
        If transaction was marked as rollback-only.
        Returns:
        True if transaction can only be rolled back.

      • close

        void close()
    throws IgniteException
        Ends the transaction. Transaction will be rolled back if it has not been committed.
        Specified by:
        close in interface AutoCloseable
        Throws:
        IgniteException - If transaction could not be gracefully ended.

      • rollbackAsync

        IgniteFuture<Void> rollbackAsync()
                          throws IgniteException
        Asynchronously rolls back this transaction. Note, that it's allowed to roll back transaction from any thread at any time.
        Returns:
        a Future representing pending completion of the rollback.
        Throws:
        IgniteException - If rollback failed.