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Remake LazyComposer interface and implementations slightly
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Replace null usages with Optional and add a bit more semantics.
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@martinfurmanski
martinfurmanski committed Jun 11, 2018
1 parent 72d46d1 commit f2e53fa
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Showing 3 changed files with 58 additions and 54 deletions.
11 changes: 6 additions & 5 deletions ...ava/org/neo4j/causalclustering/messaging/marshalling/v2/decoding/RaftMessageComposer.java
View file
Expand Up @@ -29,6 +29,7 @@
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Optional;
import java.util.Queue;

import org.neo4j.causalclustering.core.consensus.RaftMessages;
Expand Down Expand Up @@ -74,12 +75,12 @@ else if ( msg instanceof RaftMessageDecoder.ClusterIdAwareMessageComposer )
}
if ( messageComposer != null )
{
RaftMessages.ClusterIdAwareMessage clusterIdAwareMessage = messageComposer.maybeCompose( clock, raftLogEntryTerms, replicatedContents );
if ( clusterIdAwareMessage != null )
Optional<RaftMessages.ClusterIdAwareMessage> clusterIdAwareMessage = messageComposer.maybeCompose( clock, raftLogEntryTerms, replicatedContents );
clusterIdAwareMessage.ifPresent( message ->
{
clear( clusterIdAwareMessage );
out.add( clusterIdAwareMessage );
}
clear( message );
out.add( message );
} );
}
}

Expand Down
87 changes: 45 additions & 42 deletions ...java/org/neo4j/causalclustering/messaging/marshalling/v2/decoding/RaftMessageDecoder.java
View file
Expand Up @@ -29,11 +29,12 @@
import java.io.IOException;
import java.time.Clock;
import java.util.List;
import java.util.Optional;
import java.util.Queue;
import java.util.function.BiFunction;

import org.neo4j.causalclustering.catchup.Protocol;
import org.neo4j.causalclustering.core.consensus.RaftMessages;
import org.neo4j.causalclustering.core.consensus.RaftMessages.ReceivedInstantClusterIdAwareMessage;
import org.neo4j.causalclustering.core.consensus.log.RaftLogEntry;
import org.neo4j.causalclustering.core.replication.ReplicatedContent;
import org.neo4j.causalclustering.identity.ClusterId;
Expand Down Expand Up @@ -84,14 +85,14 @@ public void decode( ChannelHandlerContext ctx, ByteBuf buffer, List<Object> list
long lastLogIndex = channel.getLong();
long lastLogTerm = channel.getLong();

composer = simpleMessageComposer( new RaftMessages.Vote.Request( from, term, candidate, lastLogIndex, lastLogTerm ) );
composer = new SimpleMessageComposer( new RaftMessages.Vote.Request( from, term, candidate, lastLogIndex, lastLogTerm ) );
}
else if ( messageType.equals( VOTE_RESPONSE ) )
{
long term = channel.getLong();
boolean voteGranted = channel.get() == 1;

composer = simpleMessageComposer( new RaftMessages.Vote.Response( from, term, voteGranted ) );
composer = new SimpleMessageComposer( new RaftMessages.Vote.Response( from, term, voteGranted ) );
}
else if ( messageType.equals( PRE_VOTE_REQUEST ) )
{
Expand All @@ -101,14 +102,14 @@ else if ( messageType.equals( PRE_VOTE_REQUEST ) )
long lastLogIndex = channel.getLong();
long lastLogTerm = channel.getLong();

composer = simpleMessageComposer( new RaftMessages.PreVote.Request( from, term, candidate, lastLogIndex, lastLogTerm ) );
composer = new SimpleMessageComposer( new RaftMessages.PreVote.Request( from, term, candidate, lastLogIndex, lastLogTerm ) );
}
else if ( messageType.equals( PRE_VOTE_RESPONSE ) )
{
long term = channel.getLong();
boolean voteGranted = channel.get() == 1;

composer = simpleMessageComposer( new RaftMessages.PreVote.Response( from, term, voteGranted ) );
composer = new SimpleMessageComposer( new RaftMessages.PreVote.Response( from, term, voteGranted ) );
}
else if ( messageType.equals( APPEND_ENTRIES_REQUEST ) )
{
Expand All @@ -128,7 +129,7 @@ else if ( messageType.equals( APPEND_ENTRIES_RESPONSE ) )
long matchIndex = channel.getLong();
long appendIndex = channel.getLong();

composer = simpleMessageComposer( new RaftMessages.AppendEntries.Response( from, term, success, matchIndex, appendIndex ) );
composer = new SimpleMessageComposer( new RaftMessages.AppendEntries.Response( from, term, success, matchIndex, appendIndex ) );
}
else if ( messageType.equals( NEW_ENTRY_REQUEST ) )
{
Expand All @@ -140,18 +141,18 @@ else if ( messageType.equals( HEARTBEAT ) )
long commitIndexTerm = channel.getLong();
long commitIndex = channel.getLong();

composer = simpleMessageComposer( new RaftMessages.Heartbeat( from, leaderTerm, commitIndex, commitIndexTerm ) );
composer = new SimpleMessageComposer( new RaftMessages.Heartbeat( from, leaderTerm, commitIndex, commitIndexTerm ) );
}
else if ( messageType.equals( HEARTBEAT_RESPONSE ) )
{
composer = simpleMessageComposer( new RaftMessages.HeartbeatResponse( from ) );
composer = new SimpleMessageComposer( new RaftMessages.HeartbeatResponse( from ) );
}
else if ( messageType.equals( LOG_COMPACTION_INFO ) )
{
long leaderTerm = channel.getLong();
long prevIndex = channel.getLong();

composer = simpleMessageComposer( new RaftMessages.LogCompactionInfo( from, leaderTerm, prevIndex ) );
composer = new SimpleMessageComposer( new RaftMessages.LogCompactionInfo( from, leaderTerm, prevIndex ) );
}
else
{
Expand All @@ -173,18 +174,10 @@ static class ClusterIdAwareMessageComposer
this.clusterId = clusterId;
}

RaftMessages.ClusterIdAwareMessage maybeCompose( Clock clock, Queue<Long> logEntryTerms, Queue<ReplicatedContent> replicatedContents )
Optional<RaftMessages.ClusterIdAwareMessage> maybeCompose( Clock clock, Queue<Long> terms, Queue<ReplicatedContent> contents )
{
RaftMessages.RaftMessage composedMessage = composer.apply( logEntryTerms, replicatedContents );

if ( composedMessage != null )
{
return RaftMessages.ReceivedInstantClusterIdAwareMessage.of( clock.instant(), clusterId, composedMessage );
}
else
{
return null;
}
return composer.maybeComplete( terms, contents )
.map( m -> ReceivedInstantClusterIdAwareMessage.of( clock.instant(), clusterId, m ) );
}
}

Expand All @@ -194,19 +187,31 @@ private MemberId retrieveMember( ReadableChannel buffer ) throws IOException, En
return memberIdMarshal.unmarshal( buffer );
}

/**
* Builds the raft message. Should return {@code null} if provided collections does not contain enough data for building the message.
*/
interface LazyComposer extends BiFunction<Queue<Long>,Queue<ReplicatedContent>,RaftMessages.RaftMessage>
interface LazyComposer
{
/**
* Builds the complete raft message if provided collections contain enough data for building the complete message.
*/
Optional<RaftMessages.RaftMessage> maybeComplete( Queue<Long> terms, Queue<ReplicatedContent> contents );
}

/**
* A message without internal content components.
* A plain message without any more internal content.
*/
private static LazyComposer simpleMessageComposer( RaftMessages.RaftMessage message )
private static class SimpleMessageComposer implements LazyComposer
{
return ( terms, contents ) -> message;
private final RaftMessages.RaftMessage message;

private SimpleMessageComposer( RaftMessages.RaftMessage message )
{
this.message = message;
}

@Override
public Optional<RaftMessages.RaftMessage> maybeComplete( Queue<Long> terms, Queue<ReplicatedContent> contents )
{
return Optional.of( message );
}
}

private static class AppendEntriesComposer implements LazyComposer
Expand All @@ -229,26 +234,24 @@ private static class AppendEntriesComposer implements LazyComposer
}

@Override
public RaftMessages.BaseRaftMessage apply( Queue<Long> terms, Queue<ReplicatedContent> contents )
public Optional<RaftMessages.RaftMessage> maybeComplete( Queue<Long> terms, Queue<ReplicatedContent> contents )
{
if ( terms.size() < entryCount || contents.size() < entryCount )
{
return null;
return Optional.empty();
}
else

RaftLogEntry[] entries = new RaftLogEntry[entryCount];
for ( int i = 0; i < entryCount; i++ )
{
RaftLogEntry[] entries = new RaftLogEntry[entryCount];
for ( int i = 0; i < entryCount; i++ )
Long term = terms.poll();
if ( term == null )
{
Long term = terms.poll();
if ( term == null )
{
throw new IllegalArgumentException( "Term cannot be null" );
}
entries[i] = new RaftLogEntry( term, contents.poll() );
throw new IllegalArgumentException( "Term cannot be null" );
}
return new RaftMessages.AppendEntries.Request( from, term, prevLogIndex, prevLogTerm, entries, leaderCommit );
entries[i] = new RaftLogEntry( term, contents.poll() );
}
return Optional.of( new RaftMessages.AppendEntries.Request( from, term, prevLogIndex, prevLogTerm, entries, leaderCommit ) );
}
}

Expand All @@ -262,15 +265,15 @@ private static class NewEntryRequestComposer implements LazyComposer
}

@Override
public RaftMessages.BaseRaftMessage apply( Queue<Long> terms, Queue<ReplicatedContent> contents )
public Optional<RaftMessages.RaftMessage> maybeComplete( Queue<Long> terms, Queue<ReplicatedContent> contents )
{
if ( contents.isEmpty() )
{
return null;
return Optional.empty();
}
else
{
return new RaftMessages.NewEntry.Request( from, contents.poll() );
return Optional.of( new RaftMessages.NewEntry.Request( from, contents.poll() ) );
}
}
}
Expand Down
14 changes: 7 additions & 7 deletions ...causalclustering/messaging/marshalling/v2/decoding/ClusterIdAwareMessageComposerTest.java
View file
Expand Up @@ -27,6 +27,7 @@
import java.time.Clock;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.UUID;

import org.neo4j.causalclustering.core.consensus.RaftMessages;
Expand All @@ -40,16 +41,15 @@

public class ClusterIdAwareMessageComposerTest
{

@Test
public void shouldThrowExceptionOnConflictingMessageHeaders()
{
try
{
RaftMessageComposer raftMessageComposer = new RaftMessageComposer( Clock.systemUTC() );

raftMessageComposer.decode( null, messageCreator( ( a, b ) -> null ), null );
raftMessageComposer.decode( null, messageCreator( ( a, b ) -> null ), null );
raftMessageComposer.decode( null, messageCreator( ( a, b ) -> Optional.empty() ), null );
raftMessageComposer.decode( null, messageCreator( ( a, b ) -> Optional.empty() ), null );
}
catch ( IllegalStateException e )
{
Expand All @@ -60,7 +60,7 @@ public void shouldThrowExceptionOnConflictingMessageHeaders()
}

@Test
public void shouldThrowExceptionIfNotAllResoucesAreUsed()
public void shouldThrowExceptionIfNotAllResourcesAreUsed()
{
try
{
Expand All @@ -69,7 +69,7 @@ public void shouldThrowExceptionIfNotAllResoucesAreUsed()
ReplicatedTransaction replicatedTransaction = new ReplicatedTransaction( new byte[0] );
raftMessageComposer.decode( null, replicatedTransaction, null );
List<Object> out = new ArrayList<>();
raftMessageComposer.decode( null, messageCreator( ( a, b ) -> dummyRequest() ), out );
raftMessageComposer.decode( null, messageCreator( ( a, b ) -> Optional.of( dummyRequest() ) ), out );
}
catch ( IllegalStateException e )
{
Expand Down Expand Up @@ -102,8 +102,8 @@ private RaftMessages.PruneRequest dummyRequest()
return new RaftMessages.PruneRequest( 1 );
}

private RaftMessageDecoder.ClusterIdAwareMessageComposer messageCreator( RaftMessageDecoder.LazyComposer biFunction )
private RaftMessageDecoder.ClusterIdAwareMessageComposer messageCreator( RaftMessageDecoder.LazyComposer composer )
{
return new RaftMessageDecoder.ClusterIdAwareMessageComposer( biFunction, new ClusterId( UUID.randomUUID() ) );
return new RaftMessageDecoder.ClusterIdAwareMessageComposer( composer, new ClusterId( UUID.randomUUID() ) );
}
}

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