Slight hack of the QuerySenderListener that fixes a bug in Solr 3.5.0 where spellcheck components that use collation/onlyMorePopular with query components get stuck on Thread.wait(). Plus, it's faster.

MultithreadedQuerySenderListener.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.solr.core;

import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.apache.solr.search.SolrIndexSearcher;
import org.apache.solr.search.DocList;
import org.apache.solr.search.DocIterator;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.LocalSolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;

/**
 * Same as org.apache.solr.core, but splits up the LocalSolrQueryRequests into separate threads, for two
 * purposes:
 * 
 * 1) It's way faster when it's parallelized.
 * 
 * 2) There's a bug in the original QuerySenderListener (as of 3.5.0) that causes spellcheck components
 * that use collation (with an attached query component) to hang forever, because the thread gets stuck
 * in SolrCore at searcherLock.wait().
 * 
 * modified by Nolan Lawson
 * 
 * @version $Id: QuerySenderListener.java 1137045 2011-06-17 21:49:38Z erick $
 */
class MultithreadedQuerySenderListener extends AbstractSolrEventListener {
	
	private static final int NUM_THREADS = 8;
	
  public MultithreadedQuerySenderListener(SolrCore core) {
    super(core);
  }

  @Override
  public void newSearcher(final SolrIndexSearcher newSearcher, final SolrIndexSearcher currentSearcher) {
    final SolrIndexSearcher searcher = newSearcher;
    
    // use a fixed thread pool to avoid overhead of thread creation
    ExecutorService executorService = Executors.newFixedThreadPool(NUM_THREADS);
    
    log.info("QuerySenderListener sending requests to " + newSearcher);
    List<NamedList> allLists = (List<NamedList>)args.get("queries");
    if (allLists == null) return;
    for (final NamedList nlst : allLists) {
    	Runnable runnable = new Runnable() { 
    		public void run() {
	        	try {
	                // bind the request to a particular searcher (the newSearcher)
	                NamedList params = addEventParms(currentSearcher, nlst);
	                LocalSolrQueryRequest req = new LocalSolrQueryRequest(core,params) {
	                  @Override public SolrIndexSearcher getSearcher() { return searcher; }
	                  @Override public void close() { }
	                };
	
	                SolrQueryResponse rsp = new SolrQueryResponse();
	                core.execute(core.getRequestHandler(req.getParams().get(CommonParams.QT)), req, rsp);
	
	                // Retrieve the Document instances (not just the ids) to warm
	                // the OS disk cache, and any Solr document cache.  Only the top
	                // level values in the NamedList are checked for DocLists.
	                NamedList values = rsp.getValues();
	                for (int i=0; i<values.size(); i++) {
	                  Object o = values.getVal(i);
	                  if (o instanceof DocList) {
	                    DocList docs = (DocList)o;
	                    for (DocIterator iter = docs.iterator(); iter.hasNext();) {
	                      newSearcher.doc(iter.nextDoc());
	                    }
	                  }
	                }
	
	                req.close();
	
	              } catch (Exception e) {
	                // do nothing... we want to continue with the other requests.
	                // the failure should have already been logged.
	            	  e.printStackTrace();
	              }
              }
    	};
    	executorService.submit(runnable);
    }
    executorService.shutdown();
    log.info("QuerySenderListener done.");
  }


}