// Copyright (C) 2012 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.server.git;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.server.GerritPersonIdent;
import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
import com.google.inject.Inject;
import com.google.inject.assistedinject.Assisted;
import org.eclipse.jgit.api.errors.ConcurrentRefUpdateException;
import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.CommitBuilder;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.RefUpdate.Result;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.merge.MergeStrategy;
import org.eclipse.jgit.notes.Note;
import org.eclipse.jgit.notes.NoteMap;
import org.eclipse.jgit.notes.NoteMapMerger;
import org.eclipse.jgit.notes.NoteMerger;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import java.io.IOException;
/**
* A utility class for updating a notes branch with automatic merge of note
* trees.
*/
public class NotesBranchUtil {
public interface Factory {
NotesBranchUtil create(Project.NameKey project, Repository db,
ObjectInserter inserter);
}
private static final int MAX_LOCK_FAILURE_CALLS = 10;
private static final int SLEEP_ON_LOCK_FAILURE_MS = 25;
private final PersonIdent gerritIdent;
private final GitReferenceUpdated gitRefUpdated;
private final Project.NameKey project;
private final Repository db;
private final ObjectInserter inserter;
private RevCommit baseCommit;
private NoteMap base;
private RevCommit oursCommit;
private NoteMap ours;
private RevWalk revWalk;
private ObjectReader reader;
private boolean overwrite;
private ReviewNoteMerger noteMerger;
@Inject
public NotesBranchUtil(@GerritPersonIdent final PersonIdent gerritIdent,
final GitReferenceUpdated gitRefUpdated,
@Assisted Project.NameKey project,
@Assisted Repository db,
@Assisted ObjectInserter inserter) {
this.gerritIdent = gerritIdent;
this.gitRefUpdated = gitRefUpdated;
this.project = project;
this.db = db;
this.inserter = inserter;
}
/**
* Create a new commit in the {@code notesBranch} by updating existing
* or creating new notes from the {@code notes} map.
*
* @param notes map of notes
* @param notesBranch notes branch to update
* @param commitAuthor author of the commit in the notes branch
* @param commitMessage for the commit in the notes branch
* @throws IOException
* @throws ConcurrentRefUpdateException
*/
public final void commitAllNotes(NoteMap notes, String notesBranch,
PersonIdent commitAuthor, String commitMessage) throws IOException,
ConcurrentRefUpdateException {
this.overwrite = true;
commitNotes(notes, notesBranch, commitAuthor, commitMessage);
}
/**
* Create a new commit in the {@code notesBranch} by creating not yet
* existing notes from the {@code notes} map. The notes from the
* {@code notes} map which already exist in the note-tree of the
* tip of the {@code notesBranch} will not be updated.
*
* @param notes map of notes
* @param notesBranch notes branch to update
* @param commitAuthor author of the commit in the notes branch
* @param commitMessage for the commit in the notes branch
* @return map with those notes from the {@code notes} that were newly
* created
* @throws IOException
* @throws ConcurrentRefUpdateException
*/
public final NoteMap commitNewNotes(NoteMap notes, String notesBranch,
PersonIdent commitAuthor, String commitMessage) throws IOException,
ConcurrentRefUpdateException {
this.overwrite = false;
commitNotes(notes, notesBranch, commitAuthor, commitMessage);
NoteMap newlyCreated = NoteMap.newEmptyMap();
for (Note n : notes) {
if (base == null || !base.contains(n)) {
newlyCreated.set(n, n.getData());
}
}
return newlyCreated;
}
private void commitNotes(NoteMap notes, String notesBranch,
PersonIdent commitAuthor, String commitMessage) throws IOException,
ConcurrentRefUpdateException {
try {
revWalk = new RevWalk(db);
reader = db.newObjectReader();
loadBase(notesBranch);
if (overwrite) {
addAllNotes(notes);
} else {
addNewNotes(notes);
}
if (base != null) {
oursCommit = createCommit(ours, commitAuthor, commitMessage, baseCommit);
} else {
oursCommit = createCommit(ours, commitAuthor, commitMessage);
}
updateRef(notesBranch);
} finally {
revWalk.release();
reader.release();
}
}
private void addNewNotes(NoteMap notes) throws IOException {
for (Note n : notes) {
if (! ours.contains(n)) {
ours.set(n, n.getData());
}
}
}
private void addAllNotes(NoteMap notes) throws IOException {
for (Note n : notes) {
if (ours.contains(n)) {
// Merge the existing and the new note as if they are both new,
// means: base == null
// There is no really a common ancestry for these two note revisions
ObjectId noteContent = getNoteMerger().merge(null, n, ours.getNote(n),
reader, inserter).getData();
ours.set(n, noteContent);
} else {
ours.set(n, n.getData());
}
}
}
private NoteMerger getNoteMerger() {
if (noteMerger == null) {
noteMerger = new ReviewNoteMerger();
}
return noteMerger;
}
private void loadBase(String notesBranch) throws IOException {
Ref branch = db.getRef(notesBranch);
if (branch != null) {
baseCommit = revWalk.parseCommit(branch.getObjectId());
base = NoteMap.read(revWalk.getObjectReader(), baseCommit);
}
if (baseCommit != null) {
ours = NoteMap.read(revWalk.getObjectReader(), baseCommit);
} else {
ours = NoteMap.newEmptyMap();
}
}
private RevCommit createCommit(NoteMap map, PersonIdent author,
String message, RevCommit... parents) throws IOException {
CommitBuilder b = new CommitBuilder();
b.setTreeId(map.writeTree(inserter));
b.setAuthor(author != null ? author : gerritIdent);
b.setCommitter(gerritIdent);
if (parents.length > 0) {
b.setParentIds(parents);
}
b.setMessage(message);
ObjectId commitId = inserter.insert(b);
inserter.flush();
return revWalk.parseCommit(commitId);
}
private void updateRef(String notesBranch) throws IOException,
MissingObjectException, IncorrectObjectTypeException,
CorruptObjectException, ConcurrentRefUpdateException {
if (baseCommit != null && oursCommit.getTree().equals(baseCommit.getTree())) {
// If the trees are identical, there is no change in the notes.
// Avoid saving this commit as it has no new information.
return;
}
int remainingLockFailureCalls = MAX_LOCK_FAILURE_CALLS;
RefUpdate refUpdate = createRefUpdate(notesBranch, oursCommit, baseCommit);
for (;;) {
Result result = refUpdate.update();
if (result == Result.LOCK_FAILURE) {
if (--remainingLockFailureCalls > 0) {
try {
Thread.sleep(SLEEP_ON_LOCK_FAILURE_MS);
} catch (InterruptedException e) {
// ignore
}
} else {
throw new ConcurrentRefUpdateException("Failed to lock the ref: "
+ notesBranch, db.getRef(notesBranch), result);
}
} else if (result == Result.REJECTED) {
RevCommit theirsCommit =
revWalk.parseCommit(refUpdate.getOldObjectId());
NoteMap theirs =
NoteMap.read(revWalk.getObjectReader(), theirsCommit);
NoteMapMerger merger =
new NoteMapMerger(db, getNoteMerger(), MergeStrategy.RESOLVE);
NoteMap merged = merger.merge(base, ours, theirs);
RevCommit mergeCommit =
createCommit(merged, gerritIdent, "Merged note commits\n",
theirsCommit, oursCommit);
refUpdate = createRefUpdate(notesBranch, mergeCommit, theirsCommit);
remainingLockFailureCalls = MAX_LOCK_FAILURE_CALLS;
} else if (result == Result.IO_FAILURE) {
throw new IOException("Couldn't update " + notesBranch + ". "
+ result.name());
} else {
gitRefUpdated.fire(project, refUpdate);
break;
}
}
}
private RefUpdate createRefUpdate(String notesBranch, ObjectId newObjectId,
ObjectId expectedOldObjectId) throws IOException {
RefUpdate refUpdate = db.updateRef(notesBranch);
refUpdate.setNewObjectId(newObjectId);
if (expectedOldObjectId == null) {
refUpdate.setExpectedOldObjectId(ObjectId.zeroId());
} else {
refUpdate.setExpectedOldObjectId(expectedOldObjectId);
}
return refUpdate;
}
}