/*
 * Licensed to Elastic Search and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Elastic Search 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.merge.scheduler;

import org.apache.lucene.index.ConcurrentMergeScheduler;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.MergePolicy;
import org.apache.lucene.index.MergeScheduler;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.index.settings.IndexSettings;
import org.elasticsearch.index.shard.AbstractIndexShardComponent;
import org.elasticsearch.index.shard.ShardId;

import java.io.IOException;

/**
 * @author kimchy (shay.banon)
 */
public class ConcurrentMergeSchedulerProvider extends AbstractIndexShardComponent implements MergeSchedulerProvider {

    private final int maxThreadCount;

    @Inject public ConcurrentMergeSchedulerProvider(ShardId shardId, @IndexSettings Settings indexSettings) {
        super(shardId, indexSettings);

        // TODO LUCENE MONITOR this will change in Lucene 4.0
        this.maxThreadCount = componentSettings.getAsInt("max_thread_count", 1);
        logger.debug("using [concurrent] merge scheduler with max_thread_count[{}]", maxThreadCount);
    }

    @Override public MergeScheduler newMergeScheduler() {
        ConcurrentMergeScheduler concurrentMergeScheduler = new CustomConcurrentMergeScheduler();
        concurrentMergeScheduler.setMaxThreadCount(maxThreadCount);
        return concurrentMergeScheduler;
    }

    private class CustomConcurrentMergeScheduler extends ConcurrentMergeScheduler {

        @Override protected MergeThread getMergeThread(IndexWriter writer, MergePolicy.OneMerge merge) throws IOException {
            MergeThread thread = super.getMergeThread(writer, merge);
            thread.setName("[" + shardId.index().name() + "][" + shardId.id() + "]: " + thread.getName());
            return thread;
        }
    }
}

@@ -1829,9 +1829,80 @@
 t%22, 
-1
+Math.max(1, Math.min(3, Runtime.getRuntime().availableProcessors() / 2))
 );%0A 

Index Merge: Change default `index.merge.scheduler.max_thread_count` from ` to be adaptive based on processor count, closes #469.