/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* 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.datastax.driver.core;
import com.datastax.driver.core.policies.LoadBalancingPolicy;
import com.google.common.primitives.UnsignedBytes;
import java.util.Collection;
import java.util.Comparator;
import java.util.Iterator;
import java.util.SortedSet;
import java.util.concurrent.ConcurrentSkipListSet;
/**
* A load balancing policy that sorts hosts on the last byte of the address,
* so that the query plan is always [host1, host2, host3].
*/
public class SortingLoadBalancingPolicy implements LoadBalancingPolicy {
final SortedSet<Host> hosts = new ConcurrentSkipListSet<Host>(new Comparator<Host>() {
@Override
public int compare(Host host1, Host host2) {
byte[] address1 = host1.getAddress().getAddress();
byte[] address2 = host2.getAddress().getAddress();
return UnsignedBytes.compare(
address1[address1.length - 1],
address2[address2.length - 1]);
}
});
@Override
public void init(Cluster cluster, Collection<Host> hosts) {
this.hosts.addAll(hosts);
}
@Override
public HostDistance distance(Host host) {
return HostDistance.LOCAL;
}
@Override
public Iterator<Host> newQueryPlan(String loggedKeyspace, Statement statement) {
return hosts.iterator();
}
@Override
public void onAdd(Host host) {
onUp(host);
}
@Override
public void onUp(Host host) {
hosts.add(host);
}
@Override
public void onDown(Host host) {
hosts.remove(host);
}
@Override
public void onRemove(Host host) {
onDown(host);
}
@Override
public void close() {/*nothing to do*/}
}