/* * 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.controller.md.sal.common.api.data; import org.opendaylight.yangtools.concepts.Path; /** * Transaction enabling a client to have a combined read/write capabilities. * *
* The initial state of the write transaction is stable snapshot of current data tree * state captured when transaction was created and it's 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 represents only a proposal of state * change for data tree and it is not visible to any other concurrently running * transactions. * *
* Applications publish the changes proposed in the transaction by calling {@link #commit} * 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 #commit()} 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. * *
PATH
is A
* .
*
* * txWrite = broker.newReadWriteTransaction(); // concurrent write transaction * * txWrite.read(OPERATIONAL,PATH).get() // will return Optional containing A * txWrite.put(OPERATIONAL,PATH,B); // writes B to PATH * txWrite.read(OPERATIONAL,PATH).get() // will return Optional Containing B * * txWrite.commit().get(); // data tree is updated, PATH contains B * * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B ** * As you could see read-write transaction provides capabilities as * {@link AsyncWriteTransaction} but also allows for reading proposed changes as * if they already happened. * *
PATH
is A
.
*
* * txRead = broker.newReadOnlyTransaction(); // read Transaction is snapshot of data * txWrite = broker.newReadWriteTransaction(); // concurrent write transaction * * txRead.read(OPERATIONAL,PATH).get(); // will return Optional containing A * txWrite.read(OPERATIONAL,PATH).get() // will return Optional containing A * * txWrite.put(OPERATIONAL,PATH,B); // writes B to PATH * txWrite.read(OPERATIONAL,PATH).get() // will return Optional Containing B * * txRead.read(OPERATIONAL,PATH).get(); // concurrent read transaction still returns * // Optional containing A * * txWrite.commit().get(); // data tree is updated, PATH contains B * txRead.read(OPERATIONAL,PATH).get(); // still returns Optional containing A * * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B ** *
PATH
is A
.
*
* * tx1 = broker.newReadWriteTransaction(); // read Transaction is snapshot of data * tx2 = broker.newReadWriteTransaction(); // concurrent write transaction * * tx1.read(OPERATIONAL,PATH).get(); // will return Optional containing A * tx2.read(OPERATIONAL,PATH).get() // will return Optional containing A * * tx2.put(OPERATIONAL,PATH,B); // writes B to PATH * tx2.read(OPERATIONAL,PATH).get() // will return Optional Containing B * * tx1.read(OPERATIONAL,PATH).get(); // tx1 read-write transaction still sees Optional * // containing A since is isolated from tx2 * tx1.put(OPERATIONAL,PATH,C); // writes C to PATH * tx1.read(OPERATIONAL,PATH).get() // will return Optional Containing C * * tx2.read(OPERATIONAL,PATH).get() // tx2 read-write transaction still sees Optional * // containing B since is isolated from tx1 * * tx2.commit().get(); // data tree is updated, PATH contains B * tx1.read(OPERATIONAL,PATH).get(); // still returns Optional containing C since is isolated from tx2 * * tx1afterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state * tx1afterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B * * tx1.commit() // Will fail with OptimisticLockFailedException * // which means concurrent transaction changed the same PATH * ** *
* Note: examples contains blocking calls on future only to illustrate * that action happened after other asynchronous action. Use of blocking call * {@link com.google.common.util.concurrent.ListenableFuture#get()} is discouraged for most uses and you should * use * {@link com.google.common.util.concurrent.Futures#addCallback(com.google.common.util.concurrent.ListenableFuture, com.google.common.util.concurrent.FutureCallback)} * or other functions from {@link com.google.common.util.concurrent.Futures} to * register more specific listeners. * * @see AsyncReadTransaction * @see AsyncWriteTransaction * * @param
* Type of path (subtree identifier), which represents location in
* tree
* @param , D> extends AsyncReadTransaction ,
AsyncWriteTransaction {
}