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MessageGate.java
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MessageGate.java
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/*
* Copyright (c) 2002-2018 "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.messaging;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
import org.neo4j.causalclustering.protocol.handshake.GateEvent;
/**
* Gates messages and keeps them on a queue until the gate is either
* opened successfully or closed forever.
*/
@ChannelHandler.Sharable
public class MessageGate extends ChannelDuplexHandler
{
private final Predicate<Object> gated;
private List<GatedWrite> pending = new ArrayList<>();
public MessageGate( Predicate<Object> gated )
{
this.gated = gated;
}
@Override
public void userEventTriggered( ChannelHandlerContext ctx, Object evt ) throws Exception
{
if ( evt instanceof GateEvent )
{
if ( GateEvent.getSuccess().equals( evt ) )
{
for ( GatedWrite write : pending )
{
ctx.write( write.msg, write.promise );
}
ctx.channel().pipeline().remove( this );
}
pending.clear();
pending = null;
}
else
{
super.userEventTriggered( ctx, evt );
}
}
@Override
public void write( ChannelHandlerContext ctx, Object msg, ChannelPromise promise )
{
if ( !gated.test( msg ) )
{
ctx.write( msg, promise );
}
else if ( pending != null )
{
pending.add( new GatedWrite( msg, promise ) );
}
else
{
promise.setFailure( new RuntimeException( "Gate failed and has been permanently closed." ) );
}
}
static class GatedWrite
{
final Object msg;
final ChannelPromise promise;
GatedWrite( Object msg, ChannelPromise promise )
{
this.msg = msg;
this.promise = promise;
}
}
}