* Initial state of write transaction is a stable snapshot of the current data tree. * The state is captured when the transaction is created and its state and underlying * data tree are not affected by other concurrently running transactions. * *
* Write transactions are isolated from other concurrent write transactions. All * writes are local to the transaction and represent only a proposal of state * change for the data tree and it is not visible to any other concurrently running * transaction. * *
* Applications make changes to the local data tree in the transaction by via the * put, merge, and delete operations. * *
* Performing the following put operations: * *
* 1) container { list [ a ] }
* 2) container { list [ b ] }
*
*
* * will result in the following data being present: * *
* container { list [ b ] }
*
* * Performing the following merge operations: * *
* 1) container { list [ a ] }
* 2) container { list [ b ] }
*
*
* * will result in the following data being present: * *
* container { list [ a, b ] }
*
*
* * This also means that storing the container will preserve any * augmentations which have been attached to it. * *
* After applying changes to the local data tree, applications publish the changes proposed in the * transaction by calling {@link #submit} on the transaction. This seals the transaction * (preventing any further writes using this transaction) and submits it to be * processed and applied to global conceptual data tree. * *
* The transaction commit may fail due to a concurrent transaction modifying and committing data in * an incompatible way. See {@link #submit} for more concrete commit failure examples. * *
* Implementation Note: This interface is not intended to be implemented * by users of MD-SAL, but only to be consumed by them. * * @param
* Type of path (subtree identifier), which represents location in
* tree
* @param , D> extends AsyncTransaction
* Transactions can only be cancelled if it's state is new or submitted.
*
*
* Invoking cancel() on a failed or cancelled transaction will have no effect, and transaction
* is considered cancelled.
*
*
* Invoking cancel() on a finished transaction (future returned by {@link #submit()} already completed will always
* fail (return false).
*
* @return false if the task could not be cancelled, typically because it has already completed normally
* true otherwise
*
*/
boolean cancel();
/**
* Removes a piece of data from specified path. This operation does not fail
* if the specified path does not exist.
*
* @param store
* Logical data store which should be modified
* @param path
* Data object path
* @throws IllegalStateException
* if the transaction as already been submitted or cancelled
*/
void delete(LogicalDatastoreType store, P path);
/**
* Submits this transaction to be asynchronously applied to update the logical data tree.
* The returned CheckedFuture conveys the result of applying the data changes.
*
*
* Note: It is strongly recommended to process the CheckedFuture result in an asynchronous
* manner rather than using the blocking get() method. See example usage below.
*
*
* This call logically seals the transaction, which prevents the client from
* further changing data tree using this transaction. Any subsequent calls to
* {@link #delete(LogicalDatastoreType, Path)} will fail with
* {@link IllegalStateException}.
*
*
* The transaction is marked as submitted and enqueued into the data store back-end for processing.
*
*
* Whether or not the commit is successful is determined by versioning
* of the data tree and validation of registered commit participants
* ({@link AsyncConfigurationCommitHandler}) if the transaction changes the data tree.
*
*
* The effects of a successful commit of data depends on data change listeners
* ({@link AsyncDataChangeListener}) and commit participants
* ({@link AsyncConfigurationCommitHandler}) that are registered with the data broker.
*
*
* Transaction may fail because of multiple reasons, such as
*
* There are several sets of changes which could be considered incompatible
* between two transactions which are derived from same initial state.
* Rules for conflict detection applies recursively for each subtree
* level.
*
*
* Following table shows state changes and failures between two concurrent transactions,
* which are based on same initial state, Tx 1 completes successfully
* before Tx 2 is submitted.
*
*
* Following table shows state changes and failures between two concurrent transactions,
* which are based on same initial state, Tx 1 completes successfully
* before Tx 2 is submitted.
*
*
* This example illustrates two concurrent transactions, which derived from
* same initial state of data tree and proposes conflicting modifications.
*
*
* Commit of transaction A will be processed asynchronously and data tree
* will be updated to contain value
* Commit of Transaction B will fail, because previous transaction also
* modified path in a concurrent way. The state introduced by transaction B
* will not be applied. Returned {@link ListenableFuture} object will fail
* with {@link OptimisticLockFailedException} exception, which indicates to
* client that concurrent transaction prevented the submitted transaction from being
* applied.
* Example usage:
*
* private void doWrite( final int tries ) {
* WriteTransaction writeTx = dataBroker.newWriteOnlyTransaction();
*
* MyDataObject data = ...;
* InstanceIdentifier<MyDataObject> path = ...;
* writeTx.put( LogicalDatastoreType.OPERATIONAL, path, data );
*
* Futures.addCallback( writeTx.submit(), new FutureCallback<Void>() {
* public void onSuccess( Void result ) {
* // succeeded
* }
*
* public void onFailure( Throwable t ) {
* if( t instanceof OptimisticLockFailedException ) {
* if( ( tries - 1 ) > 0 ) {
* // do retry
* doWrite( tries - 1 );
* } else {
* // out of retries
* }
* } else {
* // failed due to another type of TransactionCommitFailedException.
* }
* } );
* }
* ...
* doWrite( 2 );
*
* Failure scenarios
*
*
*
*
* Change compatibility
*
* Change compatibility of leafs, leaf-list items
*
*
*
*
* Initial state Tx 1 Tx 2 Result Empty put(A,1) put(A,2) Tx 2 will fail, state is A=1 Empty put(A,1) merge(A,2) A=2 Empty merge(A,1) put(A,2) Tx 2 will fail, state is A=1 Empty merge(A,1) merge(A,2) A=2 A=0 put(A,1) put(A,2) Tx 2 will fail, A=1 A=0 put(A,1) merge(A,2) A=2 A=0 merge(A,1) put(A,2) Tx 2 will fail, A=1 A=0 merge(A,1) merge(A,2) A=2 A=0 delete(A) put(A,2) Tx 2 will fail, A does not exists A=0 delete(A) merge(A,2) A=2 Change compatibility of subtrees
*
*
*
*
*
* Initial state Tx 1 Tx 2 Result Empty put(TOP,[]) put(TOP,[]) Tx 2 will fail, state is TOP=[] Empty put(TOP,[]) merge(TOP,[]) TOP=[] Empty put(TOP,[FOO=1]) put(TOP,[BAR=1]) Tx 2 will fail, state is TOP=[FOO=1]
* Empty put(TOP,[FOO=1]) merge(TOP,[BAR=1]) TOP=[FOO=1,BAR=1] Empty merge(TOP,[FOO=1]) put(TOP,[BAR=1]) Tx 2 will fail, state is TOP=[FOO=1]
* Empty merge(TOP,[FOO=1]) merge(TOP,[BAR=1]) TOP=[FOO=1,BAR=1] TOP=[] put(TOP,[FOO=1]) put(TOP,[BAR=1]) Tx 2 will fail, state is TOP=[FOO=1]
* TOP=[] put(TOP,[FOO=1]) merge(TOP,[BAR=1]) state is TOP=[FOO=1,BAR=1] TOP=[] merge(TOP,[FOO=1]) put(TOP,[BAR=1]) Tx 2 will fail, state is TOP=[FOO=1]
* TOP=[] merge(TOP,[FOO=1]) merge(TOP,[BAR=1]) state is TOP=[FOO=1,BAR=1] TOP=[] delete(TOP) put(TOP,[BAR=1]) Tx 2 will fail, state is empty store
* TOP=[] delete(TOP) merge(TOP,[BAR=1]) state is TOP=[BAR=1] TOP=[] put(TOP/FOO,1) put(TOP/BAR,1]) state is TOP=[FOO=1,BAR=1] TOP=[] put(TOP/FOO,1) merge(TOP/BAR,1) state is TOP=[FOO=1,BAR=1] TOP=[] merge(TOP/FOO,1) put(TOP/BAR,1) state is TOP=[FOO=1,BAR=1] TOP=[] merge(TOP/FOO,1) merge(TOP/BAR,1) state is TOP=[FOO=1,BAR=1] TOP=[] delete(TOP) put(TOP/BAR,1) Tx 2 will fail, state is empty store TOP=[] delete(TOP) merge(TOP/BAR,1] Tx 2 will fail, state is empty store
* TOP=[FOO=1] put(TOP/FOO,2) put(TOP/BAR,1) state is TOP=[FOO=2,BAR=1] TOP=[FOO=1] put(TOP/FOO,2) merge(TOP/BAR,1) state is TOP=[FOO=2,BAR=1] TOP=[FOO=1] merge(TOP/FOO,2) put(TOP/BAR,1) state is TOP=[FOO=2,BAR=1] TOP=[FOO=1] merge(TOP/FOO,2) merge(TOP/BAR,1) state is TOP=[FOO=2,BAR=1]
* TOP=[FOO=1] delete(TOP/FOO) put(TOP/BAR,1) state is TOP=[BAR=1] TOP=[FOO=1] delete(TOP/FOO) merge(TOP/BAR,1] state is TOP=[BAR=1] Examples of failure scenarios
*
* Conflict of two transactions
*
*
* txA = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
* txB = broker.newWriteTransaction(); // allocates new transaction, data tree is empty
*
* txA.put(CONFIGURATION, PATH, A); // writes to PATH value A
* txB.put(CONFIGURATION, PATH, B) // writes to PATH value B
*
* ListenableFuture futureA = txA.submit(); // transaction A is sealed and submitted
* ListenebleFuture futureB = txB.submit(); // transaction B is sealed and submitted
*
*
* A for PATH.
* Returned {@link ListenableFuture} will successfully complete once
* state is applied to data tree.
*
*
* @return a CheckFuture containing the result of the commit. The Future blocks until the
* commit operation is complete. A successful commit returns nothing. On failure,
* the Future will fail with a {@link TransactionCommitFailedException} or an exception
* derived from TransactionCommitFailedException.
*
* @throws IllegalStateException
* if the transaction is not new
*/
CheckedFuture