com.datastax.oss.driver.internal.core.loadbalancing.helper.LocalDcHelper Maven / Gradle / Ivy
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* 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.
*/
package com.datastax.oss.driver.internal.core.loadbalancing.helper;
import com.datastax.oss.driver.api.core.loadbalancing.LoadBalancingPolicy;
import com.datastax.oss.driver.api.core.metadata.Node;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.Map;
import java.util.Optional;
import java.util.UUID;
import net.jcip.annotations.ThreadSafe;
@FunctionalInterface
@ThreadSafe
public interface LocalDcHelper {
/**
* Returns the local datacenter, if it can be discovered, or returns {@link Optional#empty empty}
* otherwise.
*
* Implementors may choose to throw {@link IllegalStateException} instead of returning {@link
* Optional#empty empty}, if they require a local datacenter to be defined in order to operate
* properly.
*
* @param nodes All the nodes that were known to exist in the cluster (regardless of their state)
* when the load balancing policy was {@linkplain LoadBalancingPolicy#init(Map,
* LoadBalancingPolicy.DistanceReporter) initialized}. This argument is provided in case
* implementors need to inspect the cluster topology to discover the local datacenter.
* @return The local datacenter, or {@link Optional#empty empty} if none found.
* @throws IllegalStateException if the local datacenter could not be discovered, and this policy
* cannot operate without it.
*/
@NonNull
Optional discoverLocalDc(@NonNull Map nodes);
}