1 /*
2 * Copyright (C) 2016, Google Inc.
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.internal.ketch;
45
46 import java.io.IOException;
47 import java.util.List;
48
49 import org.eclipse.jgit.lib.AnyObjectId;
50 import org.eclipse.jgit.transport.ReceiveCommand;
51
52 /**
53 * One round-trip to all replicas proposing a log entry.
54 * <p>
55 * In Raft a log entry represents a state transition at a specific index in the
56 * replicated log. The leader can only append log entries to the log.
57 * <p>
58 * In Ketch a log entry is recorded under the {@code refs/txn} namespace. This
59 * occurs when:
60 * <ul>
61 * <li>a replica wants to establish itself as a new leader by proposing a new
62 * term (see {@link ElectionRound})
63 * <li>an established leader wants to gain consensus on new {@link Proposal}s
64 * (see {@link ProposalRound})
65 * </ul>
66 */
67 abstract class Round {
68 final KetchLeader leader;
69 final LogIndex acceptedOldIndex;
70 LogIndex acceptedNewIndex;
71 List<ReceiveCommand> stageCommands;
72
73 Round(KetchLeader leader, LogIndex head) {
74 this.leader = leader;
75 this.acceptedOldIndex = head;
76 }
77
78 /**
79 * Creates a commit for {@code refs/txn/accepted} and calls
80 * {@link #runAsync(AnyObjectId)} to begin execution of the round across
81 * the system.
82 * <p>
83 * If references are being updated (such as in a {@link ProposalRound}) the
84 * RefTree may be modified.
85 * <p>
86 * Invoked without {@link KetchLeader#lock} to build objects.
87 *
88 * @throws IOException
89 * the round cannot build new objects within the leader's
90 * repository. The leader may be unable to execute.
91 */
92 abstract void start() throws IOException;
93
94 /**
95 * Asynchronously distribute the round's new value for
96 * {@code refs/txn/accepted} to all replicas.
97 * <p>
98 * Invoked by {@link #start()} after new commits have been created for the
99 * log. The method passes {@code newId} to {@link KetchLeader} to be
100 * distributed to all known replicas.
101 *
102 * @param newId
103 * new value for {@code refs/txn/accepted}.
104 */
105 void runAsync(AnyObjectId newId) {
106 acceptedNewIndex = acceptedOldIndex.nextIndex(newId);
107 leader.runAsync(this);
108 }
109
110 /**
111 * Notify the round it was accepted by a majority of the system.
112 * <p>
113 * Invoked by the leader with {@link KetchLeader#lock} held by the caller.
114 */
115 abstract void success();
116 }