/*
* 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
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* - Redistributions of source code must retain the above copyright
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* - Redistributions in binary form must reproduce the above
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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 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 MissingObjectException
* newId of a command is not found locally.
* @throws 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);
}
/** @return commands from this proposal. */
public Collection<Command> getCommands() {
return commands;
}
/** @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;
}
/** @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;
}
/** @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;
}
/**
* @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
* @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 State#EXECUTED} or
* {@link 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);
}
/** @return read the current state of the proposal. */
public State getState() {
return state.get();
}
/**
* @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 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 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 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();
}
}
@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());
}
}
}
}