/**
 * ============LICENSE_START=======================================================
 * org.onap.aai
 * ================================================================================
 * Copyright © 2017 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * Licensed 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.
 * ============LICENSE_END=========================================================
 *
 * ECOMP is a trademark and service mark of AT&T Intellectual Property.
 */
package org.onap.aai.util;

/*
 * logging to hbase encountered hotspotting issues, so per
 * http://archive.cloudera.com/cdh5/cdh/5/hbase-0.98.6-cdh5.3.8/book/rowkey.design.html
 * we decided to salt the rowkeys
 * as these keys are generated in a couple places, I made a class to contain that logic
 */
public class HbaseSaltPrefixer {
	private int NUM_REGION_BUCKETS = 3; //the number of hbase region servers per cluster

	private static class SingletonHolder{
		private static final HbaseSaltPrefixer INSTANCE = new HbaseSaltPrefixer();
	}
	
	/**
	 * Instantiates a new hbase salt prefixer.
	 */
	private HbaseSaltPrefixer(){}
	
	/**
	 * Gets the single instance of HbaseSaltPrefixer.
	 *
	 * @return single instance of HbaseSaltPrefixer
	 */
	public static HbaseSaltPrefixer getInstance() {
		return SingletonHolder.INSTANCE;
	}
	
	/**
	 * Prepend salt.
	 *
	 * @param key the key
	 * @return the string
	 */
	public String prependSalt(String key) {
		int salt = Math.abs(key.hashCode()) % NUM_REGION_BUCKETS;
		return salt + "-" + key;
	}
}