2 * Copyright (c) 2018 Pantheon Technologies, s.r.o. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.mdsal.dom.api;
11 * A factory which allocates new transactions to operate on the data tree.
14 * <b>Note:</b> This interface is not intended to be used directly, but rather via subinterfaces
15 * which introduces additional semantics to allocated transactions.
17 * <li> {@link DOMDataBroker}
18 * <li> {@link DOMTransactionChain}
22 * All operations on the data tree are performed via one of the transactions:
24 * <li>Read-Only - allocated using {@link #newReadOnlyTransaction()}
25 * <li>Write-Only - allocated using {@link #newWriteOnlyTransaction()}
29 * These transactions provides a stable isolated view of the data tree, which is guaranteed to be
30 * not affected by other concurrent transactions, until transaction is committed.
33 * For a detailed explanation of how transaction are isolated and how transaction-local changes are
34 * committed to global data tree, see {@link DOMDataTreeReadTransaction}, {@link DOMDataTreeWriteTransaction}
35 * and {@link DOMDataTreeWriteTransaction#commit()}.
38 * It is strongly recommended to use the type of transaction, which provides only the minimal
39 * capabilities you need. This allows for optimizations at the data broker / data store level. For
40 * example, implementations may optimize the transaction for reading if they know ahead of time that
41 * you only need to read data - such as not keeping additional meta-data, which may be required for
45 * <b>Implementation Note:</b> This interface is not intended to be implemented by users of MD-SAL,
46 * but only to be consumed by them.
49 * @see DOMTransactionChain
51 public interface DOMTransactionFactory {
53 * Allocates a new read-only transaction which provides an immutable snapshot of the data tree. The view of data
54 * tree is an immutable snapshot of current data tree state when transaction was allocated.
56 * @return A new read-only transaction
58 DOMDataTreeReadTransaction newReadOnlyTransaction();
61 * Allocates new write-only transaction based on latest state of data tree.
64 * Preconditions for mutation of data tree are captured from the snapshot of data tree state, when the transaction
65 * is allocated. If data was changed during transaction in an incompatible way then the commit of this transaction
66 * will fail. See {@link DOMDataTreeWriteTransaction#commit()} for more details about conflicting and
67 * non-conflicting changes and failure scenarios.
70 * Since this transaction does not provide a view of the data it SHOULD BE used only by callers which are exclusive
71 * writers (exporters of data) to the subtree they modify. This prevents optimistic lock failures as described in
72 * {@link DOMDataTreeWriteTransaction#commit()}.
75 * Exclusivity of writers to particular subtree SHOULD BE enforced by external locking mechanism.
77 * @return new write-only transaction
79 DOMDataTreeWriteTransaction newWriteOnlyTransaction();
82 * Allocates new read-write transaction which provides a mutable view of the data tree.
85 * Preconditions for mutation of data tree are captured from the snapshot of data tree state, when the transaction
86 * is allocated. If data was changed during transaction in an incompatible way then the commit of this transaction
87 * will fail. See {@link DOMDataTreeReadWriteTransaction#commit()} for more details about conflicting and
88 * non-conflicting changes and failure scenarios.
90 * @return new read-write transaction
92 DOMDataTreeReadWriteTransaction newReadWriteTransaction();