| /* |
| * Copyright (C) 2016, Google Inc. |
| * and other copyright owners as documented in the project's IP log. |
| * |
| * This program and the accompanying materials are made available |
| * under the terms of the Eclipse Distribution License v1.0 which |
| * accompanies this distribution, is reproduced below, and is |
| * available at http://www.eclipse.org/org/documents/edl-v10.php |
| * |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or |
| * without modification, are permitted provided that the following |
| * conditions are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * - Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following |
| * disclaimer in the documentation and/or other materials provided |
| * with the distribution. |
| * |
| * - Neither the name of the Eclipse Foundation, Inc. nor the |
| * names of its contributors may be used to endorse or promote |
| * products derived from this software without specific prior |
| * written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND |
| * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, |
| * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package org.eclipse.jgit.internal.ketch; |
| |
| import org.eclipse.jgit.lib.AnyObjectId; |
| import org.eclipse.jgit.lib.ObjectId; |
| |
| /** |
| * An ObjectId for a commit extended with incrementing log index. |
| * <p> |
| * For any two LogIndex instances, {@code A} is an ancestor of {@code C} |
| * reachable through parent edges in the graph if {@code A.index < C.index}. |
| * LogIndex provides a performance optimization for Ketch, the same information |
| * can be obtained from {@link org.eclipse.jgit.revwalk.RevWalk}. |
| * <p> |
| * Index values are only valid within a single |
| * {@link org.eclipse.jgit.internal.ketch.KetchLeader} instance after it has won |
| * an election. By restricting scope to a single leader new leaders do not need |
| * to traverse the entire history to determine the next {@code index} for new |
| * proposals. This differs from Raft, where leader election uses the log index |
| * and the term number to determine which replica holds a sufficiently |
| * up-to-date log. Since Ketch uses Git objects for storage of its replicated |
| * log, it keeps the term number as Raft does but uses standard Git operations |
| * to imply the log index. |
| * <p> |
| * {@link org.eclipse.jgit.internal.ketch.Round#runAsync(AnyObjectId)} bumps the |
| * index as each new round is constructed. |
| */ |
| public class LogIndex extends ObjectId { |
| static LogIndex unknown(AnyObjectId id) { |
| return new LogIndex(id, 0); |
| } |
| |
| private final long index; |
| |
| private LogIndex(AnyObjectId id, long index) { |
| super(id); |
| this.index = index; |
| } |
| |
| LogIndex nextIndex(AnyObjectId id) { |
| return new LogIndex(id, index + 1); |
| } |
| |
| /** |
| * Get index provided by the current leader instance. |
| * |
| * @return index provided by the current leader instance. |
| */ |
| public long getIndex() { |
| return index; |
| } |
| |
| /** |
| * Check if this log position committed before another log position. |
| * <p> |
| * Only valid for log positions in memory for the current leader. |
| * |
| * @param c |
| * other (more recent) log position. |
| * @return true if this log position was before {@code c} or equal to c and |
| * therefore any agreement of {@code c} implies agreement on this |
| * log position. |
| */ |
| boolean isBefore(LogIndex c) { |
| return index <= c.index; |
| } |
| |
| /** |
| * Create string suitable for debug logging containing the log index and |
| * abbreviated ObjectId. |
| * |
| * @return string suitable for debug logging containing the log index and |
| * abbreviated ObjectId. |
| */ |
| @SuppressWarnings("boxing") |
| public String describeForLog() { |
| return String.format("%5d/%s", index, abbreviate(6).name()); //$NON-NLS-1$ |
| } |
| |
| /** {@inheritDoc} */ |
| @SuppressWarnings("boxing") |
| @Override |
| public String toString() { |
| return String.format("LogId[%5d/%s]", index, name()); //$NON-NLS-1$ |
| } |
| } |