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ConnectWithinDataCenterStrategy.java
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ConnectWithinDataCenterStrategy.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.causalclustering.readreplica;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Random;
import java.util.stream.Collectors;
import org.neo4j.causalclustering.core.CausalClusteringSettings;
import org.neo4j.causalclustering.discovery.ReadReplicaInfo;
import org.neo4j.causalclustering.identity.MemberId;
import org.neo4j.helpers.Service;
@Service.Implementation(UpstreamDatabaseSelectionStrategy.class)
public class ConnectWithinDataCenterStrategy extends UpstreamDatabaseSelectionStrategy
{
private Random random = new Random();
public ConnectWithinDataCenterStrategy()
{
super( "connect-within-data-center" );
}
@Override
public Optional<MemberId> upstreamDatabase() throws UpstreamDatabaseSelectionException
{
Map<MemberId, ReadReplicaInfo> replicas = topologyService.readReplicas().members();
List<String> tags = config.get( CausalClusteringSettings.server_tags );
if ( tags.isEmpty() )
{
return Optional.empty();
}
String myTag = tags.get( 0 );
List<Map.Entry<MemberId, ReadReplicaInfo>> choices = replicas.entrySet().stream()
.filter( entry -> entry.getValue().tags().contains( myTag ) && !entry.getKey().equals( myself ) )
.collect( Collectors.toList() );
if ( choices.isEmpty() )
{
return Optional.empty();
}
else
{
return Optional.of( choices.get( random.nextInt( choices.size() ) ).getKey() );
}
}
}