com.google.gerrit.server.notedb.ChangeNotesCache.java Source code

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Here is the source code for com.google.gerrit.server.notedb.ChangeNotesCache.java

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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.notedb;

import com.google.auto.value.AutoValue;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.cache.Cache;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.client.RefNames;
import com.google.gerrit.server.cache.CacheModule;
import com.google.gerrit.server.notedb.AbstractChangeNotes.Args;
import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
import com.google.inject.Inject;
import com.google.inject.Module;
import com.google.inject.Singleton;
import com.google.inject.name.Named;

import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.lib.ObjectId;

import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;

@Singleton
public class ChangeNotesCache {
    @VisibleForTesting
    static final String CACHE_NAME = "change_notes";

    public static Module module() {
        return new CacheModule() {
            @Override
            protected void configure() {
                bind(ChangeNotesCache.class);
                cache(CACHE_NAME, Key.class, ChangeNotesState.class).maximumWeight(1000);
            }
        };
    }

    @AutoValue
    public abstract static class Key {
        abstract Project.NameKey project();

        abstract Change.Id changeId();

        abstract ObjectId id();
    }

    @AutoValue
    abstract static class Value {
        abstract ChangeNotesState state();

        /**
         * The {@link RevisionNoteMap} produced while parsing this change.
         * <p>
         * These instances are mutable and non-threadsafe, so it is only safe to
         * return it to the caller that actually incurred the cache miss. It is only
         * used as an optimization; {@link ChangeNotes} is capable of lazily loading
         * it as necessary.
         */
        @Nullable
        abstract RevisionNoteMap revisionNoteMap();
    }

    private class Loader implements Callable<ChangeNotesState> {
        private final Key key;
        private final ChangeNotesRevWalk rw;

        private RevisionNoteMap revisionNoteMap;

        private Loader(Key key, ChangeNotesRevWalk rw) {
            this.key = key;
            this.rw = rw;
        }

        @Override
        public ChangeNotesState call() throws ConfigInvalidException, IOException {
            ChangeNotesParser parser = new ChangeNotesParser(key.changeId(), key.id(), rw, args.noteUtil,
                    args.metrics);
            ChangeNotesState result = parser.parseAll();
            // This assignment only happens if call() was actually called, which only
            // happens when Cache#get(K, Callable<V>) incurs a cache miss.
            revisionNoteMap = parser.getRevisionNoteMap();
            return result;
        }
    }

    private final Cache<Key, ChangeNotesState> cache;
    private final Args args;

    @Inject
    ChangeNotesCache(@Named(CACHE_NAME) Cache<Key, ChangeNotesState> cache, Args args) {
        this.cache = cache;
        this.args = args;
    }

    Value get(Project.NameKey project, Change.Id changeId, ObjectId metaId, ChangeNotesRevWalk rw)
            throws IOException {
        try {
            Key key = new AutoValue_ChangeNotesCache_Key(project, changeId, metaId.copy());
            Loader loader = new Loader(key, rw);
            ChangeNotesState s = cache.get(key, loader);
            return new AutoValue_ChangeNotesCache_Value(s, loader.revisionNoteMap);
        } catch (ExecutionException e) {
            throw new IOException(String.format("Error loading %s in %s at %s", RefNames.changeMetaRef(changeId),
                    project, metaId.name()), e);
        }
    }
}