/**
* Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
*
* 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.
*/
package com.linkedin.pinot.transport.common;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.http.annotation.ThreadSafe;
import com.linkedin.pinot.common.response.ServerInstance;
/**
* Maintains next pointer per segment basis. Expected to be thread-safe
*
*/
@ThreadSafe
public class RoundRobinReplicaSelection extends ReplicaSelection {
private final Map<SegmentId, AtomicInteger> _nextPositionMap;
public RoundRobinReplicaSelection() {
_nextPositionMap = new ConcurrentHashMap<SegmentId, AtomicInteger>();
}
@Override
public void reset(SegmentId p) {
_nextPositionMap.remove(p);
}
@Override
public void reset(SegmentIdSet pg) {
for (SegmentId p : pg.getSegments()) {
reset(p);
}
}
@Override
public ServerInstance selectServer(SegmentId p, List<ServerInstance> orderedServers, Object bucketKey) {
int size = orderedServers.size();
if (size <= 0) {
return null;
}
AtomicInteger a = _nextPositionMap.get(p);
// Create a new position tracker for the partition if it is not available
if (null == a) {
synchronized (this) {
a = _nextPositionMap.get(p);
if (null == a) {
a = new AtomicInteger(-1);
_nextPositionMap.put(p, a);
}
}
}
return orderedServers.get(Math.abs(a.incrementAndGet()) % size);
}
}