org.apache.geode.cache

## Interface CacheTransactionManager

-     public interface CacheTransactionManager

  The CacheTransactionManager interface allows applications to manage transactions on a per `Cache` basis.

  The life cycle of a GemFire transaction starts with a begin operation. The life cycle ends with either a commit or rollback operation. Between the begin and the commit/rollback are typically `Region` operations. In general, those that either create, destroy, invalidate or update `Region.Entry` are considered transactional, that is they modify transactional state.

  A GemFire transaction may involve operations on multiple regions, each of which may have different attributes.

  While a GemFire transaction and its operations are invoked in the local VM, the resulting transaction state is distributed to other VM's at commit time as per the attributes of each participant Region.

  A transaction can have no more than one thread associated with it and conversely a thread can only operate on one transaction at any given time. Child threads will not inherit the existing transaction.

  Each of the following methods operate on the current thread. All methods throw `CacheClosedException` if the Cache is closed.

  GemFire Transactions currently only support Read Committed isolation. In addition, they are optimistic transactions in that write locking and conflict checks are performed as part of the commit operation.

  For guaranteed Read Committed isolation, avoid making "in place" changes, because such changes will be "seen" by other transactions and break the Read Committed isolation guarantee. e.g.

       CacheTransactionManager txMgr = cache.getCacheTransactionManager();
       txMgr.begin();
       StringBuffer s = (StringBuffer) r.get("stringBuf");
       s.append("Changes seen before commit. NOT Read Committed!");
       r.put("stringBuf", s);
       txMgr.commit();

  To aid in creating copies, the "copy on read" `Cache` attribute and the `CopyHelper.copy(T)` method are provided. The following is a Read Committed safe example using the `CopyHelper.copy` method.

       CacheTransactionManager txMgr = cache.getCacheTransactionManager();
       txMgr.begin();
       Object o = r.get("stringBuf");
       StringBuffer s = (StringBuffer) CopyHelper.copy(o);
       s.append("Changes unseen before commit. Read Committed.");
       r.put("stringBuf", s);
       txMgr.commit();

  Its important to note that creating copies can negatively impact both performance and memory consumption.

  Partitioned Regions, Distributed No Ack and Distributed Ack Regions are supported (see `AttributesFactory` for Scope). For both scopes, a consistent configuration (per VM) is enforced.

  Global Regions, client Regions (see org.apache.geode.cache.client package) and persistent Regions (see `DiskWriteAttributes`) do not support transactions.

  When PartitionedRegions are involved in a transaction, all data in the transaction must be colocated together on one data node. See the GemFire Developer Guide for details on using transactions with Partitioned Regions.

  Since:
    GemFire 4.0
  See Also:
    `Cache`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods Deprecated Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addListener(TransactionListener aListener)` Adds a transaction listener to the end of the list of transaction listeners on this cache.
    `void` | `begin()` Creates a new transaction and associates it with the current thread.
    `void` | `commit()` Commit the transaction associated with the current thread.
    `boolean` | `exists()` Reports the existence of a Transaction for this thread
    `boolean` | `exists(TransactionId transactionId)` Reports the existence of a transaction for the given transactionId.
    `TransactionListener` | `getListener()` Deprecated. as of GemFire 5.0, use `getListeners()` instead
    `TransactionListener[]` | `getListeners()` Returns an array of all the transaction listeners on this cache.
    `TransactionId` | `getTransactionId()` Returns the transaction identifier for the current thread
    `TransactionWriter` | `getWriter()` Returns the current `TransactionWriter`
    `void` | `initListeners(TransactionListener[] newListeners)` Removes all transaction listeners, calling `CacheCallback.close()` on each of them, and then adds each listener in the specified array.
    `boolean` | `isDistributed()` Returns the execution mode of transactions
    `boolean` | `isSuspended(TransactionId transactionId)` This method can be used to determine if a transaction with the given transaction identifier is currently suspended locally.
    `void` | `removeListener(TransactionListener aListener)` Removes a transaction listener from the list of transaction listeners on this cache.
    `void` | `resume(TransactionId transactionId)` On the current thread, resumes a transaction that was previously suspended using `suspend()`
    `void` | `rollback()` Roll back the transaction associated with the current thread.
    `void` | `setDistributed(boolean distributed)` Sets whether transactions should be executed in distributed or non-distributed mode.
    `TransactionListener` | `setListener(TransactionListener newListener)` Deprecated. as of GemFire 5.0, use `addListener(org.apache.geode.cache.TransactionListener)` or `initListeners(org.apache.geode.cache.TransactionListener[])` instead.
    `void` | `setWriter(TransactionWriter writer)` Set the TransactionWriter for the cache
    `TransactionId` | `suspend()` Suspends the transaction on the current thread.
    `boolean` | `tryResume(TransactionId transactionId)` On the current thread, resumes a transaction that was previously suspended using `suspend()`.
    `boolean` | `tryResume(TransactionId transactionId, long time, java.util.concurrent.TimeUnit unit)` On the current thread, resumes a transaction that was previously suspended using `suspend()`, or waits for the specified timeout interval if the transaction has not been suspended.

- - ### Method Detail

    - #### begin

          void begin()

      Creates a new transaction and associates it with the current thread.
      Throws:
        `java.lang.IllegalStateException` - if the thread is already associated with a transaction
      Since:
        GemFire 4.0

    - #### commit

          void commit()
               throws CommitConflictException

      Commit the transaction associated with the current thread. If the commit operation fails due to a conflict it will destroy the transaction state and throw a `CommitConflictException`. If the commit operation succeeds, it returns after the transaction state has been merged with committed state. When this method completes, the thread is no longer associated with a transaction.
      Throws:
        `java.lang.IllegalStateException` - if the thread is not associated with a transaction
        `CommitConflictException` - if the commit operation fails due to a write conflict.
        `TransactionDataNodeHasDepartedException` - if the node hosting the transaction data has departed. This is only relevant for transaction that involve PartitionedRegions.
        `TransactionDataNotColocatedException` - if at commit time, the data involved in the transaction has moved away from the transaction hosting node. This can only happen if rebalancing/recovery happens during a transaction that involves a PartitionedRegion.
        `TransactionInDoubtException` - when GemFire cannot tell which nodes have applied the transaction and which have not. This only occurs if nodes fail mid-commit, and only then in very rare circumstances.

    - #### rollback

          void rollback()

      Roll back the transaction associated with the current thread. When this method completes, the thread is no longer associated with a transaction and the transaction context is destroyed.
      Throws:
        `java.lang.IllegalStateException` - if the thread is not associated with a transaction
      Since:
        GemFire 4.0

    - #### suspend

          TransactionId suspend()

      Suspends the transaction on the current thread. All subsequent operations performed by this thread will be non-transactional. The suspended transaction can be resumed by calling `resume(TransactionId)`
      Returns:
        the transaction identifier of the suspended transaction or null if the thread was not associated with a transaction
      Since:
        GemFire 6.6.2

    - #### resume

          void resume(TransactionId transactionId)

      On the current thread, resumes a transaction that was previously suspended using `suspend()`
      Parameters:
        `transactionId` - the transaction to resume
      Throws:
        `java.lang.IllegalStateException` - if the thread is associated with a transaction or if `isSuspended(TransactionId)` would return false for the given transactionId
      Since:
        GemFire 6.6.2
      See Also:
        `tryResume(TransactionId)`

    - #### isSuspended

          boolean isSuspended(TransactionId transactionId)

      This method can be used to determine if a transaction with the given transaction identifier is currently suspended locally. This method does not check other members for transaction status.
      Returns:
        true if the transaction is in suspended state, false otherwise
      Since:
        GemFire 6.6.2
      See Also:
        `exists(TransactionId)`

    - #### tryResume

          boolean tryResume(TransactionId transactionId)

      On the current thread, resumes a transaction that was previously suspended using `suspend()`. This method is equivalent to

           if (isSuspended(txId)) {
             resume(txId);
           }

      except that this action is performed atomically
      Parameters:
        `transactionId` - the transaction to resume
      Returns:
        true if the transaction was resumed, false otherwise
      Since:
        GemFire 6.6.2

    - #### tryResume

          boolean tryResume(TransactionId transactionId,
                            long time,
                            java.util.concurrent.TimeUnit unit)

      On the current thread, resumes a transaction that was previously suspended using `suspend()`, or waits for the specified timeout interval if the transaction has not been suspended. This method will return if:
      - Another thread suspends the transaction
      - Another thread calls commit/rollback on the transaction
      - This thread has waited for the specified timeout
      This method returns immediately if `exists(TransactionId)` returns false.
      Parameters:
        `transactionId` - the transaction to resume
        `time` - the maximum time to wait
        `unit` - the time unit of the `time` argument
      Returns:
        true if the transaction was resumed, false otherwise
      Since:
        GemFire 6.6.2
      See Also:
        `tryResume(TransactionId)`

    - #### exists

          boolean exists(TransactionId transactionId)

      Reports the existence of a transaction for the given transactionId. This method can be used to determine if a transaction with the given transaction identifier is currently in progress locally.
      Parameters:
        `transactionId` - the given transaction identifier
      Returns:
        true if the transaction is in progress, false otherwise.
      Since:
        GemFire 6.6.2
      See Also:
        `isSuspended(TransactionId)`

    - #### exists

          boolean exists()

      Reports the existence of a Transaction for this thread
      Returns:
        true if a transaction exists, false otherwise
      Since:
        GemFire 4.0

    - #### getTransactionId

          TransactionId getTransactionId()

      Returns the transaction identifier for the current thread
      Returns:
        the transaction identifier or null if no transaction exists
      Since:
        GemFire 4.0

    - #### getListener

          @Deprecated
          TransactionListener getListener()

      Deprecated. as of GemFire 5.0, use `getListeners()` instead
      Gets the transaction listener for this Cache.
      Returns:
        The TransactionListener instance or null if no listener.
      Throws:
        `java.lang.IllegalStateException` - if more than one listener exists on this cache

    - #### getListeners

          TransactionListener[] getListeners()

      Returns an array of all the transaction listeners on this cache. Modifications to the returned array will not effect what listeners are on this cache.
      Returns:
        the cache's `TransactionListener`s; an empty array if no listeners
      Since:
        GemFire 5.0

    - #### setListener

          @Deprecated
          TransactionListener setListener(TransactionListener newListener)

      Deprecated. as of GemFire 5.0, use `addListener(org.apache.geode.cache.TransactionListener)` or `initListeners(org.apache.geode.cache.TransactionListener[])` instead.
      Sets the transaction listener for this Cache.
      Parameters:
        `newListener` - the TransactionListener to register with the Cache. Use a `null` to deregister the current listener without registering a new one.
      Returns:
        the previous TransactionListener
      Throws:
        `java.lang.IllegalStateException` - if more than one listener exists on this cache

    - #### addListener

          void addListener(TransactionListener aListener)

      Adds a transaction listener to the end of the list of transaction listeners on this cache.
      Parameters:
        `aListener` - the user defined transaction listener to add to the cache.
      Throws:
        `java.lang.IllegalArgumentException` - if `aListener` is null
      Since:
        GemFire 5.0

    - #### removeListener

          void removeListener(TransactionListener aListener)

      Removes a transaction listener from the list of transaction listeners on this cache. Does nothing if the specified listener has not been added. If the specified listener has been added then `CacheCallback.close()` will be called on it; otherwise does nothing.
      Parameters:
        `aListener` - the transaction listener to remove from the cache.
      Throws:
        `java.lang.IllegalArgumentException` - if `aListener` is null
      Since:
        GemFire 5.0

    - #### initListeners

          void initListeners(TransactionListener[] newListeners)

      Removes all transaction listeners, calling `CacheCallback.close()` on each of them, and then adds each listener in the specified array.
      Parameters:
        `newListeners` - a possibly null or empty array of listeners to add to this cache.
      Throws:
        `java.lang.IllegalArgumentException` - if the `newListeners` array has a null element
      Since:
        GemFire 5.0

    - #### setWriter

          void setWriter(TransactionWriter writer)

      Set the TransactionWriter for the cache
      Since:
        GemFire 6.5
      See Also:
        `TransactionWriter`

    - #### getWriter

          TransactionWriter getWriter()

      Returns the current `TransactionWriter`
      Returns:
        the current `TransactionWriter`
      Since:
        GemFire 6.5
      See Also:
        `setWriter(TransactionWriter)`

    - #### setDistributed

          void setDistributed(boolean distributed)

      Sets whether transactions should be executed in distributed or non-distributed mode. Once set this mode should not be changed during the course of transactions.
      Throws:
        `java.lang.IllegalStateException` - if a transaction is already in progress and this method sets the distributed mode to a different value.
      Since:
        Geode 1.0

    - #### isDistributed

          boolean isDistributed()

      Returns the execution mode of transactions
      Returns:
        true if distributed, false otherwise.
      Since:
        Geode 1.0