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// 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.git;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.server.cache.PerThreadCache;
import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Collectors;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.Repository;
/**
* {@link RefCache} backed directly by a repository. TODO: DO NOT MERGE
* PerThreadCache.CacheStalenessCheck into stable-3.2 onwards.
*/
public class RepoRefCache implements RefCache {
/**
* System property for enabling the check for stale cache entries. TODO: DO NOT MERGE into
* stable-3.2 onwards.
*/
public static final String REPO_REF_CACHE_CHECK_STALE_ENTRIES_PROPERTY =
"RepoRefCache_checkStaleEntries";
private static FluentLogger log = FluentLogger.forEnclosingClass();
private final RefDatabase refdb;
private final Map<String, Optional<ObjectId>> ids;
private final Repository repo;
private final boolean checkStaleEntries;
private final AtomicBoolean closed;
public static Optional<RefCache> getOptional(Repository repo) {
PerThreadCache cache = PerThreadCache.get();
if (cache != null && cache.allowRefCache()) {
return cache
.getWithLoader(
PerThreadCache.Key.create(RepoRefCache.class, repo),
() -> new RepoRefCache(repo),
RepoRefCache::close)
.map(c -> (RefCache) c);
}
return Optional.empty();
}
public RepoRefCache(Repository repo) {
checkStaleEntries =
Boolean.valueOf(System.getProperty(REPO_REF_CACHE_CHECK_STALE_ENTRIES_PROPERTY, "false"));
repo.incrementOpen();
this.repo = repo;
this.refdb = repo.getRefDatabase();
this.ids = new HashMap<>();
this.closed = new AtomicBoolean();
}
@Override
public Optional<ObjectId> get(String refName) throws IOException {
Optional<ObjectId> id = ids.get(refName);
if (id != null) {
return id;
}
Ref ref = refdb.exactRef(refName);
id = Optional.ofNullable(ref).map(Ref::getObjectId);
ids.put(refName, id);
return id;
}
/** @return an unmodifiable view of the refs that have been cached by this instance. */
public Map<String, Optional<ObjectId>> getCachedRefs() {
return Collections.unmodifiableMap(ids);
}
@Override
public void close() {
if (closed.getAndSet(true)) {
log.atWarning().log("RepoRefCache of {} closed more than once", repo.getDirectory());
return;
}
if (checkStaleEntries) {
checkStaleness();
}
repo.close();
}
/** TODO: DO NOT MERGE into stable-3.2 onwards. */
@VisibleForTesting
void checkStaleness() {
List<String> staleRefs = staleRefs();
if (staleRefs.size() > 0) {
throw new IllegalStateException(
"Repository "
+ repo
+ " had modifications on refs "
+ staleRefs
+ " during a readonly window");
}
}
private List<String> staleRefs() {
return ids.entrySet().stream()
.filter(this::isStale)
.map(Map.Entry::getKey)
.collect(Collectors.toList());
}
private boolean isStale(Map.Entry<String, Optional<ObjectId>> refEntry) {
String refName = refEntry.getKey();
Optional<ObjectId> id = ids.get(refName);
if (id == null) {
return false;
}
try {
ObjectId diskId = refdb.exactRef(refName).getObjectId();
boolean isStale = !Optional.ofNullable(diskId).equals(id);
if (isStale) {
log.atSevere().log(
"Repository "
+ repo
+ " has a stale ref "
+ refName
+ " (cache="
+ id
+ ", disk="
+ diskId
+ ")");
}
return isStale;
} catch (IOException e) {
log.atSevere().withCause(e).log(
"Unable to check if ref={} from repository={} is stale", refName, repo);
return true;
}
}
}
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