/*
* 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.policies;
import com.datastax.driver.core.Host;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableSet;
import java.net.InetSocketAddress;
import java.util.Collection;
/**
* A load balancing policy wrapper that ensure that only hosts from a provided
* white list will ever be returned.
* <p/>
* This policy wraps another load balancing policy and will delegate the choice
* of hosts to the wrapped policy with the exception that only hosts contained
* in the white list provided when constructing this policy will ever be
* returned. Any host not in the while list will be considered {@code IGNORED}
* and thus will not be connected to.
* <p/>
* This policy can be useful to ensure that the driver only connects to a
* predefined set of hosts. Keep in mind however that this policy defeats
* somewhat the host auto-detection of the driver. As such, this policy is only
* useful in a few special cases or for testing, but is not optimal in general.
* If all you want to do is limiting connections to hosts of the local
* data-center then you should use DCAwareRoundRobinPolicy and *not* this policy
* in particular.
*
* @see HostFilterPolicy
*/
public class WhiteListPolicy extends HostFilterPolicy {
/**
* Creates a new policy that wraps the provided child policy but only "allows" hosts
* from the provided while list.
*
* @param childPolicy the wrapped policy.
* @param whiteList the white listed hosts. Only hosts from this list may get connected
* to (whether they will get connected to or not depends on the child policy).
*/
public WhiteListPolicy(LoadBalancingPolicy childPolicy, Collection<InetSocketAddress> whiteList) {
super(childPolicy, buildPredicate(whiteList));
}
private static Predicate<Host> buildPredicate(Collection<InetSocketAddress> whiteList) {
final ImmutableSet<InetSocketAddress> hosts = ImmutableSet.copyOf(whiteList);
return new Predicate<Host>() {
@Override
public boolean apply(Host host) {
return hosts.contains(host.getSocketAddress());
}
};
}
}