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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.index.shard;
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.apache.lucene.search.IndexSearcher;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
import org.elasticsearch.index.engine.Engine;
import java.io.IOException;
/**
* Extension point to add custom functionality at request time to the {@link DirectoryReader}
* and {@link IndexSearcher} managed by the {@link IndexShard}.
*/
public class IndexSearcherWrapper {
/**
* Wraps the given {@link DirectoryReader}. The wrapped reader can filter out document just like delete documents etc. but
* must not change any term or document content.
* <p>
* NOTE: The wrapper has a per-request lifecycle, must delegate {@link IndexReader#getReaderCacheHelper()},
* {@link LeafReader#getCoreCacheHelper()} and must be an instance of {@link FilterDirectoryReader} that
* eventually exposes the original reader via {@link FilterDirectoryReader#getDelegate()}.
* The returned reader is closed once it goes out of scope.
* </p>
* @param reader The provided directory reader to be wrapped to add custom functionality
* @return a new directory reader wrapping the provided directory reader or if no wrapping was performed
* the provided directory reader
*/
protected DirectoryReader wrap(DirectoryReader reader) throws IOException {
return reader;
}
/**
* @param searcher The provided index searcher to be wrapped to add custom functionality
* @return a new index searcher wrapping the provided index searcher or if no wrapping was performed
* the provided index searcher
*/
protected IndexSearcher wrap(IndexSearcher searcher) throws IOException {
return searcher;
}
/**
* If there are configured {@link IndexSearcherWrapper} instances, the {@link IndexSearcher} of the provided engine searcher
* gets wrapped and a new {@link Engine.Searcher} instances is returned, otherwise the provided {@link Engine.Searcher} is returned.
*
* This is invoked each time a {@link Engine.Searcher} is requested to do an operation. (for example search)
*/
public final Engine.Searcher wrap(Engine.Searcher engineSearcher) throws IOException {
final ElasticsearchDirectoryReader elasticsearchDirectoryReader = ElasticsearchDirectoryReader.getElasticsearchDirectoryReader(engineSearcher.getDirectoryReader());
if (elasticsearchDirectoryReader == null) {
throw new IllegalStateException("Can't wrap non elasticsearch directory reader");
}
NonClosingReaderWrapper nonClosingReaderWrapper = new NonClosingReaderWrapper(engineSearcher.getDirectoryReader());
DirectoryReader reader = wrap(nonClosingReaderWrapper);
if (reader != nonClosingReaderWrapper) {
if (reader.getReaderCacheHelper() != elasticsearchDirectoryReader.getReaderCacheHelper()) {
throw new IllegalStateException("wrapped directory reader doesn't delegate IndexReader#getCoreCacheKey, wrappers must override this method and delegate" +
" to the original readers core cache key. Wrapped readers can't be used as cache keys since their are used only per request which would lead to subtle bugs");
}
if (ElasticsearchDirectoryReader.getElasticsearchDirectoryReader(reader) != elasticsearchDirectoryReader) {
// prevent that somebody wraps with a non-filter reader
throw new IllegalStateException("wrapped directory reader hides actual ElasticsearchDirectoryReader but shouldn't");
}
}
final IndexSearcher origIndexSearcher = engineSearcher.searcher();
final IndexSearcher innerIndexSearcher = new IndexSearcher(reader);
innerIndexSearcher.setQueryCache(origIndexSearcher.getQueryCache());
innerIndexSearcher.setQueryCachingPolicy(origIndexSearcher.getQueryCachingPolicy());
innerIndexSearcher.setSimilarity(origIndexSearcher.getSimilarity(true));
// TODO: Right now IndexSearcher isn't wrapper friendly, when it becomes wrapper friendly we should revise this extension point
// For example if IndexSearcher#rewrite() is overwritten than also IndexSearcher#createNormalizedWeight needs to be overwritten
// This needs to be fixed before we can allow the IndexSearcher from Engine to be wrapped multiple times
final IndexSearcher indexSearcher = wrap(innerIndexSearcher);
if (reader == nonClosingReaderWrapper && indexSearcher == innerIndexSearcher) {
return engineSearcher;
} else {
return new Engine.Searcher(engineSearcher.source(), indexSearcher) {
@Override
public void close() throws ElasticsearchException {
try {
reader().close();
// we close the reader to make sure wrappers can release resources if needed....
// our NonClosingReaderWrapper makes sure that our reader is not closed
} catch (IOException e) {
throw new ElasticsearchException("failed to close reader", e);
} finally {
engineSearcher.close();
}
}
};
}
}
private static final class NonClosingReaderWrapper extends FilterDirectoryReader {
private NonClosingReaderWrapper(DirectoryReader in) throws IOException {
super(in, new SubReaderWrapper() {
@Override
public LeafReader wrap(LeafReader reader) {
return reader;
}
});
}
@Override
protected DirectoryReader doWrapDirectoryReader(DirectoryReader in) throws IOException {
return new NonClosingReaderWrapper(in);
}
@Override
protected void doClose() throws IOException {
// don't close here - mimic the MultiReader#doClose = false behavior that FilterDirectoryReader doesn't have
}
@Override
public CacheHelper getReaderCacheHelper() {
return in.getReaderCacheHelper();
}
}
}