package org.apache.helix.tools;
/*
* 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.
*/
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.TreeMap;
import org.apache.helix.ZNRecord;
import org.apache.helix.model.IdealState.IdealStateProperty;
/*
* Ideal state calculator for the cluster manager V1. The ideal state is
* calculated by randomly assign master partitions to storage nodes.
*
* Note that the following code is a native strategy and is for cluster manager V1 only. We will
* use the other algorithm to calculate the ideal state in future milestones.
*
*
* */
public class IdealStateCalculatorByShuffling
{
/*
* Given the number of nodes, partitions and replica number, calculate the
* ideal state in the following manner: For the master partition assignment,
* 1. construct Arraylist partitionList, with partitionList[i] = i; 2. Shuffle
* the partitions array 3. Scan the shuffled array, then assign
* partitionList[i] to node (i % nodes)
*
* for the slave partitions, simply put them in the node after the node that
* contains the master partition.
*
* The result of the method is a ZNRecord, which contains a list of maps; each
* map is from the name of nodes to either "MASTER" or "SLAVE".
*/
public static ZNRecord calculateIdealState(List<String> instanceNames,
int partitions, int replicas, String dbName, long randomSeed)
{
return calculateIdealState(instanceNames, partitions, replicas, dbName, randomSeed, "MASTER", "SLAVE");
}
public static ZNRecord calculateIdealState(List<String> instanceNames,
int partitions, int replicas, String dbName, long randomSeed, String masterValue, String slaveValue)
{
if (instanceNames.size() <= replicas)
{
throw new IllegalArgumentException(
"Replicas must be less than number of storage nodes");
}
Collections.sort(instanceNames);
ZNRecord result = new ZNRecord(dbName);
List<Integer> partitionList = new ArrayList<Integer>(partitions);
for (int i = 0; i < partitions; i++)
{
partitionList.add(new Integer(i));
}
Random rand = new Random(randomSeed);
// Shuffle the partition list
Collections.shuffle(partitionList, rand);
for (int i = 0; i < partitionList.size(); i++)
{
int partitionId = partitionList.get(i);
Map<String, String> partitionAssignment = new TreeMap<String, String>();
int masterNode = i % instanceNames.size();
// the first in the list is the node that contains the master
partitionAssignment.put(instanceNames.get(masterNode), masterValue);
// for the jth replica, we put it on (masterNode + j) % nodes-th
// node
for (int j = 1; j <= replicas; j++)
{
int index = (masterNode + j * partitionList.size()) % instanceNames.size();
while(partitionAssignment.keySet().contains(instanceNames.get(index)))
{
index = (index +1) % instanceNames.size();
}
partitionAssignment
.put(instanceNames.get(index),
slaveValue);
}
String partitionName = dbName + "_" + partitionId;
result.setMapField(partitionName, partitionAssignment);
}
result.setSimpleField(IdealStateProperty.NUM_PARTITIONS.toString(), String.valueOf(partitions));
return result;
}
public static ZNRecord calculateIdealState(List<String> instanceNames,
int partitions, int replicas, String dbName)
{
long randomSeed = 888997632;
// seed is a constant, so that the shuffle always give same result
return calculateIdealState(instanceNames, partitions, replicas, dbName,
randomSeed);
}
}