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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.common.lucene.index;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.FilterDirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.LeafReader;
import org.elasticsearch.common.SuppressForbidden;
import org.elasticsearch.index.shard.ShardId;
import java.io.IOException;
/**
* A {@link org.apache.lucene.index.FilterDirectoryReader} that exposes
* Elasticsearch internal per shard / index information like the shard ID.
*/
public final class ElasticsearchDirectoryReader extends FilterDirectoryReader {
private final ShardId shardId;
private final FilterDirectoryReader.SubReaderWrapper wrapper;
private ElasticsearchDirectoryReader(DirectoryReader in, FilterDirectoryReader.SubReaderWrapper wrapper, ShardId shardId) throws IOException {
super(in, wrapper);
this.wrapper = wrapper;
this.shardId = shardId;
}
/**
* Returns the shard id this index belongs to.
*/
public ShardId shardId() {
return this.shardId;
}
@Override
public CacheHelper getReaderCacheHelper() {
// safe to delegate since this reader does not alter the index
return in.getReaderCacheHelper();
}
@Override
protected DirectoryReader doWrapDirectoryReader(DirectoryReader in) throws IOException {
return new ElasticsearchDirectoryReader(in, wrapper, shardId);
}
/**
* Wraps the given reader in a {@link org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader} as
* well as all it's sub-readers in {@link org.elasticsearch.common.lucene.index.ElasticsearchLeafReader} to
* expose the given shard Id.
*
* @param reader the reader to wrap
* @param shardId the shard ID to expose via the elasticsearch internal reader wrappers.
*/
public static ElasticsearchDirectoryReader wrap(DirectoryReader reader, ShardId shardId) throws IOException {
return new ElasticsearchDirectoryReader(reader, new SubReaderWrapper(shardId), shardId);
}
private static final class SubReaderWrapper extends FilterDirectoryReader.SubReaderWrapper {
private final ShardId shardId;
SubReaderWrapper(ShardId shardId) {
this.shardId = shardId;
}
@Override
public LeafReader wrap(LeafReader reader) {
return new ElasticsearchLeafReader(reader, shardId);
}
}
/**
* Adds the given listener to the provided directory reader. The reader must contain an {@link ElasticsearchDirectoryReader} in it's hierarchy
* otherwise we can't safely install the listener.
*
* @throws IllegalArgumentException if the reader doesn't contain an {@link ElasticsearchDirectoryReader} in it's hierarchy
*/
@SuppressForbidden(reason = "This is the only sane way to add a ReaderClosedListener")
public static void addReaderCloseListener(DirectoryReader reader, IndexReader.ClosedListener listener) {
ElasticsearchDirectoryReader elasticsearchDirectoryReader = getElasticsearchDirectoryReader(reader);
if (elasticsearchDirectoryReader == null) {
throw new IllegalArgumentException("Can't install close listener reader is not an ElasticsearchDirectoryReader/ElasticsearchLeafReader");
}
IndexReader.CacheHelper cacheHelper = elasticsearchDirectoryReader.getReaderCacheHelper();
if (cacheHelper == null) {
throw new IllegalArgumentException("Reader " + elasticsearchDirectoryReader + " does not support caching");
}
assert cacheHelper.getKey() == reader.getReaderCacheHelper().getKey();
cacheHelper.addClosedListener(listener);
}
/**
* Tries to unwrap the given reader until the first {@link ElasticsearchDirectoryReader} instance is found or <code>null</code> if no instance is found;
*/
public static ElasticsearchDirectoryReader getElasticsearchDirectoryReader(DirectoryReader reader) {
if (reader instanceof FilterDirectoryReader) {
if (reader instanceof ElasticsearchDirectoryReader) {
return (ElasticsearchDirectoryReader) reader;
} else {
// We need to use FilterDirectoryReader#getDelegate and not FilterDirectoryReader#unwrap, because
// If there are multiple levels of filtered leaf readers then with the unwrap() method it immediately
// returns the most inner leaf reader and thus skipping of over any other filtered leaf reader that
// may be instance of ElasticsearchLeafReader. This can cause us to miss the shardId.
return getElasticsearchDirectoryReader(((FilterDirectoryReader) reader).getDelegate());
}
}
return null;
}
}
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