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UpstreamDatabaseStrategySelector.java
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UpstreamDatabaseStrategySelector.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.LinkedHashSet;
import java.util.NoSuchElementException;
import org.neo4j.causalclustering.identity.MemberId;
import static org.neo4j.helpers.collection.Iterables.empty;
public class UpstreamDatabaseStrategySelector
{
private LinkedHashSet<UpstreamDatabaseSelectionStrategy> strategies = new LinkedHashSet<>();
private MemberId myself;
UpstreamDatabaseStrategySelector( UpstreamDatabaseSelectionStrategy defaultStrategy )
{
this( defaultStrategy, empty(), null );
}
UpstreamDatabaseStrategySelector( UpstreamDatabaseSelectionStrategy defaultStrategy,
Iterable<UpstreamDatabaseSelectionStrategy> otherStrategies, MemberId myself )
{
this.myself = myself;
if ( otherStrategies != null )
{
for ( UpstreamDatabaseSelectionStrategy otherStrategy : otherStrategies )
{
strategies.add( otherStrategy );
}
}
strategies.add( defaultStrategy );
}
public MemberId bestUpstreamDatabase() throws UpstreamDatabaseSelectionException
{
MemberId result = null;
for ( UpstreamDatabaseSelectionStrategy strategy : this.strategies )
{
try
{
if ( strategy.upstreamDatabase().isPresent() )
{
result = strategy.upstreamDatabase().get();
break;
}
}
catch ( NoSuchElementException ex )
{
// Do nothing, this strategy failed
}
}
if ( result == null )
{
throw new UpstreamDatabaseSelectionException(
"Could not find an upstream database with which to connect." );
}
return result;
}
}