Java tutorial
/* * 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 static org.eclipse.jgit.internal.ketch.Proposal.State.ABORTED; import static org.eclipse.jgit.internal.ketch.Proposal.State.EXECUTED; import static org.eclipse.jgit.internal.ketch.Proposal.State.NEW; import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED; import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK; import java.io.IOException; import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.concurrent.CopyOnWriteArrayList; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicReference; import org.eclipse.jgit.annotations.Nullable; import org.eclipse.jgit.errors.MissingObjectException; import org.eclipse.jgit.internal.storage.reftree.Command; import org.eclipse.jgit.lib.ObjectId; import org.eclipse.jgit.lib.PersonIdent; import org.eclipse.jgit.lib.Ref; import org.eclipse.jgit.revwalk.RevWalk; import org.eclipse.jgit.transport.PushCertificate; import org.eclipse.jgit.transport.ReceiveCommand; import org.eclipse.jgit.util.time.ProposedTimestamp; /** * A proposal to be applied in a Ketch system. * <p> * Pushing to a Ketch leader results in the leader making a proposal. The * proposal includes the list of reference updates. The leader attempts to send * the proposal to a quorum of replicas by pushing the proposal to a "staging" * area under the {@code refs/txn/stage/} namespace. If the proposal succeeds * then the changes are durable and the leader can commit the proposal. * <p> * Proposals are executed by * {@link org.eclipse.jgit.internal.ketch.KetchLeader#queueProposal(Proposal)}, * which runs them asynchronously in the background. Proposals are thread-safe * futures allowing callers to {@link #await()} for results or be notified by * callback using {@link #addListener(Runnable)}. */ public class Proposal { /** Current state of the proposal. */ public enum State { /** Proposal has not yet been given to a {@link KetchLeader}. */ NEW(false), /** * Proposal was validated and has entered the queue, but a round * containing this proposal has not started yet. */ QUEUED(false), /** Round containing the proposal has begun and is in progress. */ RUNNING(false), /** * Proposal was executed through a round. Individual results from * {@link Proposal#getCommands()}, {@link Command#getResult()} explain * the success or failure outcome. */ EXECUTED(true), /** Proposal was aborted and did not reach consensus. */ ABORTED(true); private final boolean done; private State(boolean done) { this.done = done; } /** @return true if this is a terminal state. */ public boolean isDone() { return done; } } private final List<Command> commands; private PersonIdent author; private String message; private PushCertificate pushCert; private List<ProposedTimestamp> timestamps; private final List<Runnable> listeners = new CopyOnWriteArrayList<>(); private final AtomicReference<State> state = new AtomicReference<>(NEW); /** * Create a proposal from a list of Ketch commands. * * @param cmds * prepared list of commands. */ public Proposal(List<Command> cmds) { commands = Collections.unmodifiableList(new ArrayList<>(cmds)); } /** * Create a proposal from a collection of received commands. * * @param rw * walker to assist in preparing commands. * @param cmds * list of pending commands. * @throws org.eclipse.jgit.errors.MissingObjectException * newId of a command is not found locally. * @throws java.io.IOException * local objects cannot be accessed. */ public Proposal(RevWalk rw, Collection<ReceiveCommand> cmds) throws MissingObjectException, IOException { commands = asCommandList(rw, cmds); } private static List<Command> asCommandList(RevWalk rw, Collection<ReceiveCommand> cmds) throws MissingObjectException, IOException { List<Command> commands = new ArrayList<>(cmds.size()); for (ReceiveCommand cmd : cmds) { commands.add(new Command(rw, cmd)); } return Collections.unmodifiableList(commands); } /** * Get commands from this proposal. * * @return commands from this proposal. */ public Collection<Command> getCommands() { return commands; } /** * Get optional author of the proposal. * * @return optional author of the proposal. */ @Nullable public PersonIdent getAuthor() { return author; } /** * Set the author for the proposal. * * @param who * optional identity of the author of the proposal. * @return {@code this} */ public Proposal setAuthor(@Nullable PersonIdent who) { author = who; return this; } /** * Get optional message for the commit log of the RefTree. * * @return optional message for the commit log of the RefTree. */ @Nullable public String getMessage() { return message; } /** * Set the message to appear in the commit log of the RefTree. * * @param msg * message text for the commit. * @return {@code this} */ public Proposal setMessage(@Nullable String msg) { message = msg != null && !msg.isEmpty() ? msg : null; return this; } /** * Get optional certificate signing the references. * * @return optional certificate signing the references. */ @Nullable public PushCertificate getPushCertificate() { return pushCert; } /** * Set the push certificate signing the references. * * @param cert * certificate, may be null. * @return {@code this} */ public Proposal setPushCertificate(@Nullable PushCertificate cert) { pushCert = cert; return this; } /** * Get timestamps that Ketch must block for. * * @return timestamps that Ketch must block for. These may have been used as * commit times inside the objects involved in the proposal. */ public List<ProposedTimestamp> getProposedTimestamps() { if (timestamps != null) { return timestamps; } return Collections.emptyList(); } /** * Request the proposal to wait for the affected timestamps to resolve. * * @param ts * a {@link org.eclipse.jgit.util.time.ProposedTimestamp} object. * @return {@code this}. */ public Proposal addProposedTimestamp(ProposedTimestamp ts) { if (timestamps == null) { timestamps = new ArrayList<>(4); } timestamps.add(ts); return this; } /** * Add a callback to be invoked when the proposal is done. * <p> * A proposal is done when it has entered either * {@link org.eclipse.jgit.internal.ketch.Proposal.State#EXECUTED} or * {@link org.eclipse.jgit.internal.ketch.Proposal.State#ABORTED} state. If * the proposal is already done {@code callback.run()} is immediately * invoked on the caller's thread. * * @param callback * method to run after the proposal is done. The callback may be * run on a Ketch system thread and should be completed quickly. */ public void addListener(Runnable callback) { boolean runNow = false; synchronized (state) { if (state.get().isDone()) { runNow = true; } else { listeners.add(callback); } } if (runNow) { callback.run(); } } /** Set command result as OK. */ void success() { for (Command c : commands) { if (c.getResult() == NOT_ATTEMPTED) { c.setResult(OK); } } notifyState(EXECUTED); } /** Mark commands as "transaction aborted". */ void abort() { Command.abort(commands, null); notifyState(ABORTED); } /** * Read the current state of the proposal. * * @return read the current state of the proposal. */ public State getState() { return state.get(); } /** * Whether the proposal was attempted * * @return {@code true} if the proposal was attempted. A true value does not * mean consensus was reached, only that the proposal was considered * and will not be making any more progress beyond its current * state. */ public boolean isDone() { return state.get().isDone(); } /** * Wait for the proposal to be attempted and {@link #isDone()} to be true. * * @throws java.lang.InterruptedException * caller was interrupted before proposal executed. */ public void await() throws InterruptedException { synchronized (state) { while (!state.get().isDone()) { state.wait(); } } } /** * Wait for the proposal to be attempted and {@link #isDone()} to be true. * * @param wait * how long to wait. * @param unit * unit describing the wait time. * @return true if the proposal is done; false if the method timed out. * @throws java.lang.InterruptedException * caller was interrupted before proposal executed. */ public boolean await(long wait, TimeUnit unit) throws InterruptedException { synchronized (state) { if (state.get().isDone()) { return true; } state.wait(unit.toMillis(wait)); return state.get().isDone(); } } /** * Wait for the proposal to exit a state. * * @param notIn * state the proposal should not be in to return. * @param wait * how long to wait. * @param unit * unit describing the wait time. * @return true if the proposal exited the state; false on time out. * @throws java.lang.InterruptedException * caller was interrupted before proposal executed. */ public boolean awaitStateChange(State notIn, long wait, TimeUnit unit) throws InterruptedException { synchronized (state) { if (state.get() != notIn) { return true; } state.wait(unit.toMillis(wait)); return state.get() != notIn; } } void notifyState(State s) { synchronized (state) { state.set(s); state.notifyAll(); } if (s.isDone()) { for (Runnable callback : listeners) { callback.run(); } listeners.clear(); } } /** {@inheritDoc} */ @Override public String toString() { StringBuilder s = new StringBuilder(); s.append("Ketch Proposal {\n"); //$NON-NLS-1$ s.append(" ").append(state.get()).append('\n'); //$NON-NLS-1$ if (author != null) { s.append(" author ").append(author).append('\n'); //$NON-NLS-1$ } if (message != null) { s.append(" message ").append(message).append('\n'); //$NON-NLS-1$ } for (Command c : commands) { s.append(" "); //$NON-NLS-1$ format(s, c.getOldRef(), "CREATE"); //$NON-NLS-1$ s.append(' '); format(s, c.getNewRef(), "DELETE"); //$NON-NLS-1$ s.append(' ').append(c.getRefName()); if (c.getResult() != ReceiveCommand.Result.NOT_ATTEMPTED) { s.append(' ').append(c.getResult()); // $NON-NLS-1$ } s.append('\n'); } s.append('}'); return s.toString(); } private static void format(StringBuilder s, @Nullable Ref r, String n) { if (r == null) { s.append(n); } else if (r.isSymbolic()) { s.append(r.getTarget().getName()); } else { ObjectId id = r.getObjectId(); if (id != null) { s.append(id.abbreviate(8).name()); } } } }