org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader Maven / Gradle / Ivy
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
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.core.Nullable;
import org.elasticsearch.core.SuppressForbidden;
import org.elasticsearch.index.shard.ShardId;
import org.elasticsearch.indices.ESCacheHelper;
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;
@Nullable
private final ESCacheHelper esCacheHelper;
private ElasticsearchDirectoryReader(
DirectoryReader in,
FilterDirectoryReader.SubReaderWrapper wrapper,
ShardId shardId,
@Nullable ESCacheHelper esCacheHelper
) throws IOException {
super(in, wrapper);
this.wrapper = wrapper;
this.shardId = shardId;
this.esCacheHelper = esCacheHelper;
}
/**
* 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, esCacheHelper);
}
/**
* Wraps the given reader in a {@link ElasticsearchDirectoryReader} as
* well as all it's sub-readers in {@link 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 wrap(reader, shardId, null);
}
/**
* Wraps the given reader in a {@link ElasticsearchDirectoryReader} as
* well as all it's sub-readers in {@link 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.
* @param esCacheHelper the custom {@link ESCacheHelper} implementation that doesn't tie
* its lifecycle to that of the underlying reader
*/
public static ElasticsearchDirectoryReader wrap(DirectoryReader reader, ShardId shardId, @Nullable ESCacheHelper esCacheHelper)
throws IOException {
return new ElasticsearchDirectoryReader(reader, new SubReaderWrapper(shardId), shardId, esCacheHelper);
}
/**
* Retrieves Elasticsearch's version of the reader cache helper (see {@link ESCacheHelper})
*/
public static ESCacheHelper getESReaderCacheHelper(DirectoryReader reader) {
ElasticsearchDirectoryReader esReader = getElasticsearchDirectoryReader(reader);
assert esReader != null;
// even though we assert that the reader is non-null, we are a bit lenient here,
// as falling back to the underlying cache helper does not affect correctness
if (esReader == null || esReader.esCacheHelper == null) {
return new ESCacheHelper.Wrapper(reader.getReaderCacheHelper());
}
return esReader.esCacheHelper;
}
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}
* 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;
}
}