--- /dev/null
+/*
+ * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.mdsal.common.api;
+
+import com.google.common.util.concurrent.CheckedFuture;
+import com.google.common.util.concurrent.ListenableFuture;
+import org.opendaylight.yangtools.concepts.Path;
+
+/**
+ * Write transaction provides mutation capabilities for a data tree.
+ *
+ * <p>
+ * 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.
+ * <p>
+ * 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.
+ * <p>
+ * Applications make changes to the local data tree in the transaction by via the
+ * <b>put</b>, <b>merge</b>, and <b>delete</b> operations.
+ *
+ * <h2>Put operation</h2>
+ * Stores a piece of data at a specified path. This acts as an add / replace
+ * operation, which is to say that whole subtree will be replaced by the
+ * specified data.
+ * <p>
+ * Performing the following put operations:
+ *
+ * <pre>
+ * 1) container { list [ a ] }
+ * 2) container { list [ b ] }
+ * </pre>
+ *
+ * will result in the following data being present:
+ *
+ * <pre>
+ * container { list [ b ] }
+ * </pre>
+ * <h2>Merge operation</h2>
+ * Merges a piece of data with the existing data at a specified path. Any pre-existing data
+ * which is not explicitly overwritten will be preserved. This means that if you store a container,
+ * its child lists will be merged.
+ * <p>
+ * Performing the following merge operations:
+ *
+ * <pre>
+ * 1) container { list [ a ] }
+ * 2) container { list [ b ] }
+ * </pre>
+ *
+ * will result in the following data being present:
+ *
+ * <pre>
+ * container { list [ a, b ] }
+ * </pre>
+ *
+ * This also means that storing the container will preserve any
+ * augmentations which have been attached to it.
+ *
+ * <h2>Delete operation</h2>
+ * Removes a piece of data from a specified path.
+ * <p>
+ * 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.
+ * <p>
+ * 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.
+ * <p>
+ * <b>Implementation Note:</b> This interface is not intended to be implemented
+ * by users of MD-SAL, but only to be consumed by them.
+ *
+ * @param <P>
+ * Type of path (subtree identifier), which represents location in
+ * tree
+ * @param <D>
+ * Type of data (payload), which represents data payload
+ */
+public interface AsyncWriteTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {
+ /**
+ * Cancels the transaction.
+ *
+ * Transactions can only be cancelled if it was not yet submited.
+ *
+ * Invoking cancel() on failed or already canceled will have no effect, and transaction is
+ * considered cancelled.
+ *
+ * Invoking cancel() on finished transaction (future returned by {@link #submit()} already
+ * successfully completed) will always fail (return false).
+ *
+ * @return <tt>false</tt> if the task could not be cancelled, typically because it has already
+ * completed normally; <tt>true</tt> 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 was submitted or canceled.
+ */
+ 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.
+ * <p>
+ * <b>Note:</b> It is strongly recommended to process the CheckedFuture result in an
+ * asynchronous manner rather than using the blocking get() method. See example usage below.
+ * <p>
+ * This call logically seals the transaction, which prevents the client from further changing
+ * data tree using this transaction. Any subsequent calls to
+ * <code>put(LogicalDatastoreType, Path, Object)</code>,
+ * <code>merge(LogicalDatastoreType, Path, Object)</code>,
+ * <code>delete(LogicalDatastoreType, Path)</code> will fail with {@link IllegalStateException}.
+ *
+ * The transaction is marked as submitted and enqueued into the data store back-end for
+ * processing.
+ *
+ * <p>
+ * Whether or not the commit is successful is determined by versioning of the data tree and
+ * validation of registered commit participants if the transaction changes the data tree.
+ * <p>
+ * The effects of a successful commit of data depends on data change listeners (
+ * {@link AsyncDataChangeListener}) and commit participants that are registered with the data
+ * broker.
+ * <p>
+ * <h3>Example usage:</h3>
+ *
+ * <pre>
+ * 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 );
+ * </pre>
+ *
+ * <h2>Failure scenarios</h2>
+ * <p>
+ * Transaction may fail because of multiple reasons, such as
+ * <ul>
+ * <li>Another transaction finished earlier and modified the same node in a non-compatible way
+ * (see below). In this case the returned future will fail with an
+ * {@link OptimisticLockFailedException}. It is the responsibility of the caller to create a new
+ * transaction and submit the same modification again in order to update data tree.
+ * <i><b>Warning</b>: In most cases, retrying after an OptimisticLockFailedException will result
+ * in a high probability of success. However, there are scenarios, albeit unusual, where any
+ * number of retries will not succeed. Therefore it is strongly recommended to limit the number
+ * of retries (2 or 3) to avoid an endless loop.</i></li>
+ * <li>Data change introduced by this transaction did not pass validation by commit handlers or
+ * data was incorrectly structured. Returned future will fail with a
+ * {@link DataValidationFailedException}. User should not retry to create new transaction with
+ * same data, since it probably will fail again.</li>
+ * </ul>
+ *
+ * <h3>Change compatibility</h3>
+ *
+ * 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.
+ *
+ * <h4>Change compatibility of leafs, leaf-list items</h4>
+ *
+ * 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.
+ *
+ * <table summary="Change compatibility of leaf values">
+ * <tr>
+ * <th>Initial state</th>
+ * <th>Tx 1</th>
+ * <th>Tx 2</th>
+ * <th>Result</th>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(A,1)</td>
+ * <td>put(A,2)</td>
+ * <td>Tx 2 will fail, state is A=1</td>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(A,1)</td>
+ * <td>merge(A,2)</td>
+ * <td>A=2</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>Empty</td>
+ * <td>merge(A,1)</td>
+ * <td>put(A,2)</td>
+ * <td>Tx 2 will fail, state is A=1</td>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>merge(A,1)</td>
+ * <td>merge(A,2)</td>
+ * <td>A=2</td>
+ * </tr>
+ *
+ *
+ * <tr>
+ * <td>A=0</td>
+ * <td>put(A,1)</td>
+ * <td>put(A,2)</td>
+ * <td>Tx 2 will fail, A=1</td>
+ * </tr>
+ * <tr>
+ * <td>A=0</td>
+ * <td>put(A,1)</td>
+ * <td>merge(A,2)</td>
+ * <td>A=2</td>
+ * </tr>
+ * <tr>
+ * <td>A=0</td>
+ * <td>merge(A,1)</td>
+ * <td>put(A,2)</td>
+ * <td>Tx 2 will fail, A=1</td>
+ * </tr>
+ * <tr>
+ * <td>A=0</td>
+ * <td>merge(A,1)</td>
+ * <td>merge(A,2)</td>
+ * <td>A=2</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>A=0</td>
+ * <td>delete(A)</td>
+ * <td>put(A,2)</td>
+ * <td>Tx 2 will fail, A does not exists</td>
+ * </tr>
+ * <tr>
+ * <td>A=0</td>
+ * <td>delete(A)</td>
+ * <td>merge(A,2)</td>
+ * <td>A=2</td>
+ * </tr>
+ * </table>
+ *
+ * <h4>Change compatibility of subtrees</h4>
+ *
+ * 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.
+ *
+ * <table summary="Change compatibility of containers">
+ * <tr>
+ * <th>Initial state</th>
+ * <th>Tx 1</th>
+ * <th>Tx 2</th>
+ * <th>Result</th>
+ * </tr>
+ *
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(TOP,[])</td>
+ * <td>put(TOP,[])</td>
+ * <td>Tx 2 will fail, state is TOP=[]</td>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(TOP,[])</td>
+ * <td>merge(TOP,[])</td>
+ * <td>TOP=[]</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(TOP,[FOO=1])</td>
+ * <td>put(TOP,[BAR=1])</td>
+ * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>put(TOP,[FOO=1])</td>
+ * <td>merge(TOP,[BAR=1])</td>
+ * <td>TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>Empty</td>
+ * <td>merge(TOP,[FOO=1])</td>
+ * <td>put(TOP,[BAR=1])</td>
+ * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
+ * </tr>
+ * <tr>
+ * <td>Empty</td>
+ * <td>merge(TOP,[FOO=1])</td>
+ * <td>merge(TOP,[BAR=1])</td>
+ * <td>TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>put(TOP,[FOO=1])</td>
+ * <td>put(TOP,[BAR=1])</td>
+ * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>put(TOP,[FOO=1])</td>
+ * <td>merge(TOP,[BAR=1])</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>merge(TOP,[FOO=1])</td>
+ * <td>put(TOP,[BAR=1])</td>
+ * <td>Tx 2 will fail, state is TOP=[FOO=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>merge(TOP,[FOO=1])</td>
+ * <td>merge(TOP,[BAR=1])</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>delete(TOP)</td>
+ * <td>put(TOP,[BAR=1])</td>
+ * <td>Tx 2 will fail, state is empty store</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>delete(TOP)</td>
+ * <td>merge(TOP,[BAR=1])</td>
+ * <td>state is TOP=[BAR=1]</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>put(TOP/FOO,1)</td>
+ * <td>put(TOP/BAR,1])</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>put(TOP/FOO,1)</td>
+ * <td>merge(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>merge(TOP/FOO,1)</td>
+ * <td>put(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>merge(TOP/FOO,1)</td>
+ * <td>merge(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=1,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>delete(TOP)</td>
+ * <td>put(TOP/BAR,1)</td>
+ * <td>Tx 2 will fail, state is empty store</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[]</td>
+ * <td>delete(TOP)</td>
+ * <td>merge(TOP/BAR,1]</td>
+ * <td>Tx 2 will fail, state is empty store</td>
+ * </tr>
+ *
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>put(TOP/FOO,2)</td>
+ * <td>put(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=2,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>put(TOP/FOO,2)</td>
+ * <td>merge(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=2,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>merge(TOP/FOO,2)</td>
+ * <td>put(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=2,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>merge(TOP/FOO,2)</td>
+ * <td>merge(TOP/BAR,1)</td>
+ * <td>state is TOP=[FOO=2,BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>delete(TOP/FOO)</td>
+ * <td>put(TOP/BAR,1)</td>
+ * <td>state is TOP=[BAR=1]</td>
+ * </tr>
+ * <tr>
+ * <td>TOP=[FOO=1]</td>
+ * <td>delete(TOP/FOO)</td>
+ * <td>merge(TOP/BAR,1]</td>
+ * <td>state is TOP=[BAR=1]</td>
+ * </tr>
+ * </table>
+ *
+ *
+ * <h3>Examples of failure scenarios</h3>
+ *
+ * <h4>Conflict of two transactions</h4>
+ *
+ * This example illustrates two concurrent transactions, which derived from same initial state
+ * of data tree and proposes conflicting modifications.
+ *
+ * <pre>
+ * 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
+ * </pre>
+ *
+ * Commit of transaction A will be processed asynchronously and data tree will be updated to
+ * contain value <code>A</code> for <code>PATH</code>. Returned {@link ListenableFuture} will
+ * successfully complete once state is applied to data tree.
+ *
+ * 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. <br>
+ *
+ * @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 already submitted or was canceled.
+ */
+ CheckedFuture<Void,TransactionCommitFailedException> submit();
+
+}
Code Review / mdsal.git / blobdiff