com.google.gerrit.server.patch.AutoMerger Maven / Gradle / Ivy
// Copyright (C) 2016 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.patch;
import static com.google.common.base.Preconditions.checkArgument;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.UsedAt;
import com.google.gerrit.entities.RefNames;
import com.google.gerrit.metrics.Counter1;
import com.google.gerrit.metrics.Description;
import com.google.gerrit.metrics.Field;
import com.google.gerrit.metrics.MetricMaker;
import com.google.gerrit.metrics.Timer1;
import com.google.gerrit.server.GerritPersonIdent;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.git.InMemoryInserter;
import com.google.gerrit.server.git.MergeUtil;
import com.google.gerrit.server.logging.Metadata;
import com.google.gerrit.server.update.RepoView;
import com.google.inject.Inject;
import java.io.IOException;
import java.util.Optional;
import org.eclipse.jgit.dircache.DirCache;
import org.eclipse.jgit.lib.CommitBuilder;
import org.eclipse.jgit.lib.Config;
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.Repository;
import org.eclipse.jgit.merge.ResolveMerger;
import org.eclipse.jgit.merge.ThreeWayMergeStrategy;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevObject;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.transport.ReceiveCommand;
/**
* Utility class for creating an auto-merge commit of a merge commit.
*
* An auto-merge commit is the result of merging the 2 parents of a merge commit automatically.
* If there are conflicts the auto-merge commit contains Git conflict markers that indicate these
* conflicts.
*
*
Creating auto-merge commits for octopus merges (merge commits with more than 2 parents) is not
* supported. In this case the auto-merge is created between the first 2 parent commits.
*
*
All created auto-merge commits are stored in the repository of their merge commit as {@code
* refs/cache-automerge/} branches. These branches serve:
*
*
* - as a cache so that the each auto-merge gets computed only once
*
- as base for merge commits on which users can comment
*
*
* The second point means that these commits are referenced from NoteDb. The consequence of this
* is that these refs should never be deleted.
*/
public class AutoMerger {
private static final FluentLogger logger = FluentLogger.forEnclosingClass();
public static final String AUTO_MERGE_MSG_PREFIX = "Auto-merge of ";
@UsedAt(UsedAt.Project.GOOGLE)
public static boolean cacheAutomerge(Config cfg) {
return cfg.getBoolean("change", null, "cacheAutomerge", true);
}
private enum OperationType {
CACHE_LOAD,
IN_MEMORY_WRITE,
ON_DISK_WRITE
}
private final Counter1 counter;
private final Timer1 latency;
private final PersonIdent gerritIdent;
private final boolean save;
private final ThreeWayMergeStrategy configuredMergeStrategy;
@Inject
AutoMerger(
MetricMaker metricMaker,
@GerritServerConfig Config cfg,
@GerritPersonIdent PersonIdent gerritIdent) {
this.counter =
metricMaker.newCounter(
"git/auto-merge/num_operations",
new Description("AutoMerge computations").setRate().setUnit("auto merge computations"),
Field.ofEnum(OperationType.class, "type", Metadata.Builder::operationName).build());
this.latency =
metricMaker.newTimer(
"git/auto-merge/latency",
new Description("AutoMerge computation latency")
.setCumulative()
.setUnit("milliseconds"),
Field.ofEnum(OperationType.class, "type", Metadata.Builder::operationName).build());
this.save = cacheAutomerge(cfg);
this.gerritIdent = gerritIdent;
this.configuredMergeStrategy = MergeUtil.getMergeStrategy(cfg);
}
/**
* Reads or creates an auto-merge commit of the parents of the given merge commit.
*
* The result is read from Git or computed in-memory and not written back to Git. This method
* exists for backwards compatibility only. All new changes have their auto-merge commits written
* transactionally when the change or patch set is created.
*
* @return auto-merge commit. Headers of the returned RevCommit are parsed.
*/
public RevCommit lookupFromGitOrMergeInMemory(
Repository repo,
RevWalk rw,
InMemoryInserter ins,
RevCommit merge,
ThreeWayMergeStrategy mergeStrategy)
throws IOException {
checkArgument(rw.getObjectReader().getCreatedFromInserter() == ins);
Optional existingCommit =
lookupCommit(repo, rw, RefNames.refsCacheAutomerge(merge.name()));
if (existingCommit.isPresent()) {
counter.increment(OperationType.CACHE_LOAD);
return existingCommit.get();
}
counter.increment(OperationType.IN_MEMORY_WRITE);
logger.atInfo().log("Computing in-memory AutoMerge for " + merge.name());
try (Timer1.Context ignored = latency.start(OperationType.IN_MEMORY_WRITE)) {
return rw.parseCommit(createAutoMergeCommit(repo.getConfig(), rw, ins, merge, mergeStrategy));
}
}
/**
* Creates an auto merge commit for the provided commit in case it is a merge commit. To be used
* whenever Gerrit creates new patch sets.
*
* Callers need to include the returned {@link ReceiveCommand} in their ref transaction.
*
* @return A {@link ReceiveCommand} wrapped in an {@link Optional} to be used in a {@link
* org.eclipse.jgit.lib.BatchRefUpdate}. {@link Optional#empty()} in case we don't need an
* auto merge commit.
*/
public Optional createAutoMergeCommitIfNecessary(
RepoView repoView, RevWalk rw, ObjectInserter ins, RevCommit maybeMergeCommit)
throws IOException {
if (maybeMergeCommit.getParentCount() != 2 || !save) {
logger.atFine().log("AutoMerge not required");
return Optional.empty();
}
ObjectId autoMerge;
try (Timer1.Context ignored = latency.start(OperationType.ON_DISK_WRITE)) {
autoMerge =
createAutoMergeCommit(
repoView.getConfig(), rw, ins, maybeMergeCommit, configuredMergeStrategy);
}
counter.increment(OperationType.ON_DISK_WRITE);
logger.atFine().log("Added %s AutoMerge ref update for commit", autoMerge.name());
return Optional.of(
new ReceiveCommand(
ObjectId.zeroId(), autoMerge, RefNames.refsCacheAutomerge(maybeMergeCommit.name())));
}
/**
* Creates an auto-merge commit of the parents of the given merge commit.
*
* @return auto-merge commit. Headers of the returned RevCommit are parsed.
*/
private ObjectId createAutoMergeCommit(
Config repoConfig,
RevWalk rw,
ObjectInserter ins,
RevCommit merge,
ThreeWayMergeStrategy mergeStrategy)
throws IOException {
rw.parseHeaders(merge);
ResolveMerger m = (ResolveMerger) mergeStrategy.newMerger(ins, repoConfig);
DirCache dc = DirCache.newInCore();
m.setDirCache(dc);
// If we don't plan on saving results, use a fully in-memory inserter.
// Using just a non-flushing wrapper is not sufficient, since in particular DfsInserter might
// try to write to storage after exceeding an internal buffer size.
m.setObjectInserter(ins instanceof InMemoryInserter ? new NonFlushingWrapper(ins) : ins);
boolean couldMerge = m.merge(merge.getParents());
ObjectId treeId;
if (couldMerge) {
treeId = m.getResultTreeId();
} else {
treeId =
MergeUtil.mergeWithConflicts(
rw,
ins,
dc,
"HEAD",
merge.getParent(0),
"BRANCH",
merge.getParent(1),
m.getMergeResults());
}
rw.parseHeaders(merge);
// For maximum stability, choose a single ident using the committer time of
// the input commit, using the server name and timezone.
PersonIdent ident =
new PersonIdent(
gerritIdent, merge.getCommitterIdent().getWhen(), gerritIdent.getTimeZone());
CommitBuilder cb = new CommitBuilder();
cb.setAuthor(ident);
cb.setCommitter(ident);
cb.setTreeId(treeId);
cb.setMessage(AUTO_MERGE_MSG_PREFIX + merge.name() + '\n');
for (RevCommit p : merge.getParents()) {
cb.addParentId(p);
}
if (ins instanceof InMemoryInserter) {
// When using an InMemoryInserter we need to read back the values from that inserter because
// they are not available.
try (ObjectReader tmpReader = ins.newReader();
RevWalk tmpRw = new RevWalk(tmpReader)) {
return tmpRw.parseCommit(ins.insert(cb));
}
}
return rw.parseCommit(ins.insert(cb));
}
private Optional lookupCommit(Repository repo, RevWalk rw, String refName)
throws IOException {
Ref ref = repo.getRefDatabase().exactRef(refName);
if (ref != null && ref.getObjectId() != null) {
RevObject obj = rw.parseAny(ref.getObjectId());
if (obj instanceof RevCommit) {
return Optional.of((RevCommit) obj);
}
}
return Optional.empty();
}
private static class NonFlushingWrapper extends ObjectInserter.Filter {
private final ObjectInserter ins;
private NonFlushingWrapper(ObjectInserter ins) {
this.ins = ins;
}
@Override
protected ObjectInserter delegate() {
return ins;
}
@Override
public void flush() {}
@Override
public void close() {}
}
}