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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.actions.cache;
import com.google.common.collect.MapMaker;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ConditionallyThreadSafe;
import com.google.devtools.build.lib.util.CanonicalStringIndexer;
import com.google.devtools.build.lib.util.Clock;
import com.google.devtools.build.lib.util.PersistentMap;
import com.google.devtools.build.lib.util.StringCanonicalizer;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentMap;
/**
* Persistent version of the CanonicalStringIndexer.
*
* <p>This class is backed by a PersistentMap that holds one direction of the
* canonicalization mapping. The other direction is handled purely in memory
* and reconstituted at load-time.
*
* <p>Thread-safety is ensured by locking on all mutating operations from the
* superclass. Read-only operations are not locked, but rather backed by
* ConcurrentMaps.
*/
@ConditionallyThreadSafe // condition: each instance must instantiated with
// different dataFile.
final class PersistentStringIndexer extends CanonicalStringIndexer {
/**
* Persistent metadata map. Used as a backing map to provide a persistent
* implementation of the metadata cache.
*/
private static final class PersistentIndexMap extends PersistentMap<String, Integer> {
private static final int VERSION = 0x01;
private static final long SAVE_INTERVAL_NS = 3L * 1000 * 1000 * 1000;
private final Clock clock;
private long nextUpdate;
public PersistentIndexMap(Path mapFile, Path journalFile, Clock clock) throws IOException {
super(VERSION, PersistentStringIndexer.<String, Integer>newConcurrentMap(INITIAL_ENTRIES),
mapFile, journalFile);
this.clock = clock;
nextUpdate = clock.nanoTime();
load(/*throwOnLoadFailure=*/true);
}
@Override
protected boolean updateJournal() {
long time = clock.nanoTime();
if (SAVE_INTERVAL_NS == 0 || time > nextUpdate) {
nextUpdate = time + SAVE_INTERVAL_NS;
return true;
}
return false;
}
@Override
public Integer remove(Object object) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
public void flush() {
super.forceFlush();
}
@Override
protected String readKey(DataInputStream in) throws IOException {
int length = in.readInt();
if (length < 0) {
throw new IOException("corrupt key length: " + length);
}
byte[] content = new byte[length];
in.readFully(content);
return StringCanonicalizer.intern(bytes2string(content));
}
@Override
protected Integer readValue(DataInputStream in) throws IOException {
return in.readInt();
}
@Override
protected void writeKey(String key, DataOutputStream out) throws IOException {
byte[] content = string2bytes(key);
out.writeInt(content.length);
out.write(content);
}
@Override
protected void writeValue(Integer value, DataOutputStream out) throws IOException {
out.writeInt(value);
}
}
private final PersistentIndexMap persistentIndexMap;
private static final int INITIAL_ENTRIES = 10000;
/**
* Instantiates and loads instance of the persistent string indexer.
*/
static PersistentStringIndexer newPersistentStringIndexer(Path dataPath,
Clock clock) throws IOException {
PersistentIndexMap persistentIndexMap = new PersistentIndexMap(dataPath,
FileSystemUtils.replaceExtension(dataPath, ".journal"), clock);
Map<Integer, String> reverseMapping = newConcurrentMap(INITIAL_ENTRIES);
for (Map.Entry<String, Integer> entry : persistentIndexMap.entrySet()) {
if (reverseMapping.put(entry.getValue(), entry.getKey()) != null) {
throw new IOException("Corrupted filename index has duplicate entry: " + entry.getKey());
}
}
return new PersistentStringIndexer(persistentIndexMap, reverseMapping);
}
private PersistentStringIndexer(PersistentIndexMap stringToInt,
Map<Integer, String> intToString) {
super(stringToInt, intToString);
this.persistentIndexMap = stringToInt;
}
/**
* Saves index data to the file.
*/
synchronized long save() throws IOException {
return persistentIndexMap.save();
}
/**
* Flushes the journal.
*/
synchronized void flush() {
persistentIndexMap.flush();
}
private static <K, V> ConcurrentMap<K, V> newConcurrentMap(int expectedCapacity) {
return new MapMaker().initialCapacity(expectedCapacity).makeMap();
}
}
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