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ConnectToRandomCoreServerStrategy.java
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ConnectToRandomCoreServerStrategy.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.Iterator;
import java.util.Optional;
import java.util.Random;
import org.neo4j.causalclustering.discovery.CoreTopology;
import org.neo4j.causalclustering.identity.MemberId;
import org.neo4j.helpers.Service;
@Service.Implementation( UpstreamDatabaseSelectionStrategy.class )
public class ConnectToRandomCoreServerStrategy extends UpstreamDatabaseSelectionStrategy
{
private final Random random = new Random();
public ConnectToRandomCoreServerStrategy()
{
super( "connect-to-random-core-server" );
}
@Override
public Optional<MemberId> upstreamDatabase() throws UpstreamDatabaseSelectionException
{
final CoreTopology coreTopology = topologyService.coreServers();
if ( coreTopology.members().size() == 0 )
{
throw new UpstreamDatabaseSelectionException( "No core servers available" );
}
int skippedServers = random.nextInt( coreTopology.members().size() );
final Iterator<MemberId> iterator = coreTopology.members().keySet().iterator();
MemberId member;
do
{
member = iterator.next();
}
while ( skippedServers-- > 0 );
return Optional.ofNullable( member );
}
}