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This component provides the means to set up a cluster of Neo4j instances that act together
as a cluster, providing Master-Slave replication and other features.
/*
* Copyright (c) 2002-2016 "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 conversationManagerFactory;
BiFunction masterFactory;
BiFunction masterServerFactory;
private Log userLog;
private HaIdGeneratorFactory idGeneratorFactory;
private Config config;
private Supplier slaveFactorySupplier;
private DelegateInvocationHandler masterDelegateHandler;
private ClusterMemberAvailability clusterMemberAvailability;
private Supplier dataSourceSupplier;
public SwitchToMaster( LogService logService,
HaIdGeneratorFactory idGeneratorFactory, Config config, Supplier slaveFactorySupplier,
Factory conversationManagerFactory,
BiFunction masterFactory,
BiFunction masterServerFactory,
DelegateInvocationHandler masterDelegateHandler, ClusterMemberAvailability clusterMemberAvailability,
Supplier dataSourceSupplier )
{
this.conversationManagerFactory = conversationManagerFactory;
this.masterFactory = masterFactory;
this.masterServerFactory = masterServerFactory;
this.userLog = logService.getUserLog( getClass() );
this.idGeneratorFactory = idGeneratorFactory;
this.config = config;
this.slaveFactorySupplier = slaveFactorySupplier;
this.masterDelegateHandler = masterDelegateHandler;
this.clusterMemberAvailability = clusterMemberAvailability;
this.dataSourceSupplier = dataSourceSupplier;
}
/**
* Performs a switch to the master state. Starts communication endpoints, switches components to the master state
* and broadcasts the appropriate Master Is Available event.
* @param haCommunicationLife The LifeSupport instance to register communication endpoints.
* @param me The URI that the communication endpoints should bind to
* @return The URI at which the master communication was bound.
*/
public URI switchToMaster( LifeSupport haCommunicationLife, URI me )
{
userLog.info( "I am %s, moving to master", myId( config ) );
// Do not wait for currently active transactions to complete before continuing switching.
// - A master in a cluster is very important, without it the cluster cannot process any write requests
// - Awaiting open transactions to complete assumes that this instance just now was a slave that is
// switching to master, which means the previous master where these active transactions were hosted
// is no longer available so these open transactions cannot continue and complete anyway,
// so what's the point waiting for them?
// - Read transactions may still be able to complete, but the correct response to failures in those
// is to have them throw transient error exceptions hinting that they should be retried,
// at which point they may get redirected to another instance, or to this instance if it has completed
// the switch until then.
idGeneratorFactory.switchToMaster();
NeoStoreDataSource neoStoreXaDataSource = dataSourceSupplier.get();
neoStoreXaDataSource.afterModeSwitch();
ConversationManager conversationManager = conversationManagerFactory.newInstance();
Master master = masterFactory.apply( conversationManager, haCommunicationLife );
MasterServer masterServer = masterServerFactory.apply( master, conversationManager );
haCommunicationLife.add( masterServer );
masterDelegateHandler.setDelegate( master );
haCommunicationLife.start();
URI masterHaURI = getMasterUri( me, masterServer, config );
clusterMemberAvailability.memberIsAvailable( MASTER, masterHaURI, neoStoreXaDataSource.getStoreId() );
userLog.info( "I am %s, successfully moved to master", myId( config ) );
slaveFactorySupplier.get().setStoreId( neoStoreXaDataSource.getStoreId() );
return masterHaURI;
}
static URI getMasterUri( URI me, MasterServer masterServer, Config config )
{
String hostname = config.get( HaSettings.ha_server ).getHost();
if ( hostname == null || hostname.contains( "0.0.0.0" ) )
{
String masterAddress = ServerUtil.getHostString( masterServer.getSocketAddress() );
hostname = masterAddress.contains( "0.0.0.0" ) ? me.getHost() : masterAddress;
}
int port = masterServer.getSocketAddress().getPort();
return URI.create( "ha://" + hostname + ":" + port + "?serverId=" + myId( config ) );
}
private static InstanceId myId( Config config )
{
return config.get( ClusterSettings.server_id );
}
@Override
public void close() throws Exception
{
userLog = null;
conversationManagerFactory = null;
masterFactory = null;
masterServerFactory = null;
idGeneratorFactory = null;
config = null;
slaveFactorySupplier = null;
masterDelegateHandler = null;
clusterMemberAvailability = null;
dataSourceSupplier = null;
}
}
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