2 * Copyright (c) 2017 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.binding.javav2.api;
10 import com.google.common.annotations.Beta;
13 * A factory which allocates new transactions to operate on the data tree.
16 * <b>Note:</b> This interface is not intended to be used directly, but rather via subinterfaces
17 * which introduces additional semantics to allocated transactions.
19 * <li> {@link DataBroker}
20 * <li> {@link TransactionChain}
24 * All operations on the data tree are performed via one of the transactions:
26 * <li>Read-Only - allocated using {@link #newReadOnlyTransaction()}
27 * <li>Write-Only - allocated using {@link #newWriteOnlyTransaction()}
31 * These transactions provides a stable isolated view of the data tree, which is guaranteed to be
32 * not affected by other concurrent transactions, until transaction is committed.
35 * For a detailed explanation of how transaction are isolated and how transaction-local changes are
36 * committed to global data tree, see {@link ReadTransaction}, {@link WriteTransaction}
37 * and {@link WriteTransaction#commit()}.
40 * It is strongly recommended to use the type of transaction, which provides only the minimal
41 * capabilities you need. This allows for optimizations at the data broker / data store level. For
42 * example, implementations may optimize the transaction for reading if they know ahead of time that
43 * you only need to read data - such as not keeping additional meta-data, which may be required for
47 * <b>Implementation Note:</b> This interface is not intended to be implemented by users of MD-SAL,
48 * but only to be consumed by them.
53 public interface TransactionFactory {
55 * Allocates a new read-only transaction which provides an immutable snapshot of the data tree. The view of data
56 * tree is an immutable snapshot of current data tree state when transaction was allocated.
58 * @return A new read-only transaction
60 ReadTransaction newReadOnlyTransaction();
63 * Allocates new write-only transaction based on latest state of data tree.
66 * Preconditions for mutation of data tree are captured from the snapshot of data tree state, when the transaction
67 * is allocated. If data was changed during transaction in an incompatible way then the commit of this transaction
68 * will fail. See {@link WriteTransaction#commit()} for more details about conflicting and not-conflicting changes
69 * and failure scenarios.
72 * Since this transaction does not provide a view of the data it SHOULD BE used only by callers who are exclusive
73 * writers (exporters of data) to the subtree they modify. This prevents optimistic lock failures as described in
74 * {@link WriteTransaction#commit()}.
77 * Exclusivity of writers to particular subtree SHOULD BE enforced by external locking mechanism.
79 * @return new write-only transaction
81 WriteTransaction newWriteOnlyTransaction();