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RaftMembershipState.java
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RaftMembershipState.java
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/*
* 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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.coreedge.raft.state.membership;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import org.neo4j.coreedge.raft.membership.RaftMembership;
import org.neo4j.coreedge.raft.state.ChannelMarshal;
import org.neo4j.coreedge.raft.state.EndOfStreamException;
import org.neo4j.coreedge.raft.state.SafeStateMarshal;
import org.neo4j.coreedge.server.CoreMember;
import org.neo4j.storageengine.api.ReadableChannel;
import org.neo4j.storageengine.api.WritableChannel;
public class RaftMembershipState implements RaftMembership
{
private Set<CoreMember> additionalReplicationMembers = new HashSet<>();
private volatile Set<CoreMember> votingMembers = new HashSet<>();
private volatile Set<CoreMember> replicationMembers = new HashSet<>(); // votingMembers + additionalReplicationMembers
private final Set<Listener> listeners;
private long logIndex = -1; // First log index is 0, so -1 is used here as "unknown" value
private RaftMembershipState( Set<CoreMember> members, long logIndex )
{
this.votingMembers = members;
this.logIndex = logIndex;
this.listeners = new HashSet<>( );
updateReplicationMembers();
}
public RaftMembershipState()
{
this.listeners = new HashSet<>();
}
public synchronized void setVotingMembers( Set<CoreMember> newVotingMembers )
{
this.votingMembers = new HashSet<>( newVotingMembers );
updateReplicationMembers();
notifyListeners();
}
/**
* Adds an additional member to replicate to. Members that are joining need to
* catch up sufficiently before they become part of the voting group.
*
* @param member The member which will be added to the replication group.
*/
public synchronized void addAdditionalReplicationMember( CoreMember member )
{
additionalReplicationMembers.add( member );
updateReplicationMembers();
notifyListeners();
}
/**
* Removes a member previously part of the additional replication member group.
*
* This either happens because they caught up sufficiently and became part of the
* voting group or because they failed to catch up in time.
*
* @param member The member to remove from the replication group.
*/
public synchronized void removeAdditionalReplicationMember( CoreMember member )
{
additionalReplicationMembers.remove( member );
updateReplicationMembers();
notifyListeners();
}
public void logIndex( long logIndex )
{
this.logIndex = logIndex;
}
private void updateReplicationMembers()
{
HashSet<CoreMember> newReplicationMembers = new HashSet<>( votingMembers );
newReplicationMembers.addAll( additionalReplicationMembers );
this.replicationMembers = newReplicationMembers;
}
@Override
public Set<CoreMember> votingMembers()
{
return new HashSet<>( votingMembers );
}
@Override
public Set<CoreMember> replicationMembers()
{
return new HashSet<>( replicationMembers );
}
@Override
public long logIndex()
{
return logIndex;
}
@Override
public synchronized void registerListener( Listener listener )
{
listeners.add( listener );
}
@Override
public synchronized void deregisterListener( Listener listener )
{
listeners.remove( listener );
}
private void notifyListeners()
{
listeners.forEach( Listener::onMembershipChanged );
}
public static class Marshal extends SafeStateMarshal<RaftMembershipState>
{
private final ChannelMarshal<CoreMember> memberMarshal;
public Marshal( ChannelMarshal<CoreMember> marshal )
{
this.memberMarshal = marshal;
}
@Override
public void marshal( RaftMembershipState state, WritableChannel channel ) throws IOException
{
channel.putLong( state.logIndex );
channel.putInt( state.votingMembers.size() );
for ( CoreMember votingMember : state.votingMembers )
{
memberMarshal.marshal( votingMember, channel );
}
}
@Override
public RaftMembershipState unmarshal0( ReadableChannel channel ) throws IOException, EndOfStreamException
{
long logIndex = channel.getLong();
int memberCount = channel.getInt();
Set<CoreMember> members = new HashSet<>();
for ( int i = 0; i < memberCount; i++ )
{
members.add( memberMarshal.unmarshal( channel ) );
}
return new RaftMembershipState( members, logIndex );
}
@Override
public RaftMembershipState startState()
{
return new RaftMembershipState();
}
@Override
public long ordinal( RaftMembershipState state )
{
return state.logIndex();
}
}
}