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CoreState.java
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CoreState.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;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import org.neo4j.coreedge.SessionTracker;
import org.neo4j.coreedge.catchup.storecopy.StoreCopyFailedException;
import org.neo4j.coreedge.discovery.CoreServerSelectionException;
import org.neo4j.coreedge.raft.RaftStateMachine;
import org.neo4j.coreedge.raft.log.RaftLog;
import org.neo4j.coreedge.raft.log.RaftLogEntry;
import org.neo4j.coreedge.raft.log.monitoring.RaftLogCommitIndexMonitor;
import org.neo4j.coreedge.raft.log.pruning.LogPruner;
import org.neo4j.coreedge.raft.log.segmented.InFlightMap;
import org.neo4j.coreedge.raft.replication.DistributedOperation;
import org.neo4j.coreedge.raft.replication.ProgressTracker;
import org.neo4j.coreedge.raft.replication.tx.CoreReplicatedContent;
import org.neo4j.coreedge.server.CoreMember;
import org.neo4j.coreedge.server.edge.CoreServerSelectionStrategy;
import org.neo4j.kernel.internal.DatabaseHealth;
import org.neo4j.kernel.lifecycle.LifecycleAdapter;
import org.neo4j.kernel.monitoring.Monitors;
import org.neo4j.logging.Log;
import org.neo4j.logging.LogProvider;
import static java.lang.Math.max;
import static java.lang.String.format;
public class CoreState extends LifecycleAdapter implements RaftStateMachine, LogPruner
{
private static final long NOTHING = -1;
private final RaftLog raftLog;
private final StateStorage<Long> lastFlushedStorage;
private final int flushEvery;
private final ProgressTracker progressTracker;
private final SessionTracker sessionTracker;
private final Supplier<DatabaseHealth> dbHealth;
private final InFlightMap<Long,RaftLogEntry> inFlightMap;
private final Log log;
private final CoreStateApplier applier;
private final CoreServerSelectionStrategy someoneElse;
private final CoreStateDownloader downloader;
private final RaftLogCommitIndexMonitor commitIndexMonitor;
private final OperationBatcher batcher;
private CoreStateMachines coreStateMachines;
private long lastApplied = NOTHING;
private long lastSeenCommitIndex = NOTHING;
private long lastFlushed = NOTHING;
public CoreState(
CoreStateMachines coreStateMachines, RaftLog raftLog,
int maxBatchSize,
int flushEvery,
Supplier<DatabaseHealth> dbHealth,
LogProvider logProvider,
ProgressTracker progressTracker,
StateStorage<Long> lastFlushedStorage,
SessionTracker sessionTracker,
CoreServerSelectionStrategy someoneElse,
CoreStateApplier applier,
CoreStateDownloader downloader,
InFlightMap<Long, RaftLogEntry> inFlightMap,
Monitors monitors )
{
this.coreStateMachines = coreStateMachines;
this.raftLog = raftLog;
this.lastFlushedStorage = lastFlushedStorage;
this.flushEvery = flushEvery;
this.progressTracker = progressTracker;
this.sessionTracker = sessionTracker;
this.someoneElse = someoneElse;
this.applier = applier;
this.downloader = downloader;
this.log = logProvider.getLog( getClass() );
this.dbHealth = dbHealth;
this.inFlightMap = inFlightMap;
this.commitIndexMonitor = monitors.newMonitor( RaftLogCommitIndexMonitor.class, getClass() );
this.batcher = new OperationBatcher( maxBatchSize );
}
@Override
public synchronized void notifyCommitted( long commitIndex )
{
assert this.lastSeenCommitIndex <= commitIndex;
if ( this.lastSeenCommitIndex < commitIndex )
{
this.lastSeenCommitIndex = commitIndex;
submitApplyJob( commitIndex );
commitIndexMonitor.commitIndex( commitIndex );
}
}
private void submitApplyJob( long lastToApply )
{
applier.submit( ( status ) -> () -> {
try ( InFlightLogEntryReader logEntrySupplier = new InFlightLogEntryReader( raftLog, inFlightMap, true ) )
{
for ( long logIndex = lastApplied + 1; !status.isCancelled() && logIndex <= lastToApply; logIndex++ )
{
RaftLogEntry entry = logEntrySupplier.get( logIndex );
if ( entry == null )
{
throw new IllegalStateException( "Committed log entry must exist." );
}
if ( entry.content() instanceof DistributedOperation )
{
DistributedOperation distributedOperation = (DistributedOperation) entry.content();
progressTracker.trackReplication( distributedOperation );
batcher.add( logIndex, distributedOperation );
}
else
{
batcher.flush();
lastApplied = logIndex;
}
}
batcher.flush();
}
catch ( Throwable e )
{
log.error( "Failed to apply up to index " + lastToApply, e );
dbHealth.get().panic( e );
}
} );
}
public synchronized long lastApplied()
{
return lastApplied;
}
private class OperationBatcher
{
private List<DistributedOperation> batch;
private int maxBatchSize;
private long lastIndex;
OperationBatcher( int maxBatchSize )
{
this.batch = new ArrayList<>( maxBatchSize );
this.maxBatchSize = maxBatchSize;
}
private void add( long index, DistributedOperation operation ) throws Exception
{
if ( batch.size() > 0 )
{
assert index == (lastIndex + 1);
}
batch.add( operation );
lastIndex = index;
if ( batch.size() == maxBatchSize )
{
flush();
}
}
private void flush() throws Exception
{
if ( batch.size() == 0 )
{
return;
}
long startIndex = lastIndex - batch.size() + 1;
handleOperations( startIndex, batch );
lastApplied = lastIndex;
batch.clear();
maybeFlush();
}
}
@Override
public synchronized void notifyNeedFreshSnapshot()
{
try
{
downloadSnapshot( someoneElse.coreServer() );
}
catch ( CoreServerSelectionException e )
{
log.error( "Failed to select server", e );
}
}
public void compact() throws IOException
{
raftLog.prune( lastFlushed );
}
/**
* Attempts to download a fresh snapshot from another core instance.
*
* @param source The source address to attempt a download of a snapshot from.
*/
public synchronized void downloadSnapshot( CoreMember source )
{
try
{
applier.sync( true );
downloader.downloadSnapshot( source, this );
}
catch ( InterruptedException | StoreCopyFailedException e )
{
log.error( "Failed to download snapshot", e );
}
}
private void handleOperations( long commandIndex, List<DistributedOperation> operations )
{
try ( CommandDispatcher dispatcher = coreStateMachines.commandDispatcher() )
{
for ( DistributedOperation operation : operations )
{
if ( !sessionTracker.validateOperation( operation.globalSession(), operation.operationId() ) )
{
commandIndex++;
continue;
}
CoreReplicatedContent command = (CoreReplicatedContent) operation.content();
command.dispatch( dispatcher, commandIndex,
result -> progressTracker.trackResult( operation, result ) );
sessionTracker.update( operation.globalSession(), operation.operationId(), commandIndex );
commandIndex++;
}
}
}
private void maybeFlush() throws IOException
{
if ( (lastApplied - lastFlushed) > flushEvery )
{
flush();
}
}
private void flush() throws IOException
{
coreStateMachines.flush();
sessionTracker.flush();
lastFlushedStorage.persistStoreData( lastApplied );
lastFlushed = lastApplied;
}
@Override
public synchronized void start() throws IOException, InterruptedException
{
lastFlushed = lastApplied = lastFlushedStorage.getInitialState();
log.info( format( "Restoring last applied index to %d", lastApplied ) );
sessionTracker.start();
/* Considering the order in which state is flushed, the state machines will
* always be furthest ahead and indicate the furthest possible state to
* which we must replay to reach a consistent state. */
long lastPossiblyApplying = max( coreStateMachines.getLastAppliedIndex(), sessionTracker.getLastAppliedIndex() );
if ( lastPossiblyApplying > lastApplied )
{
log.info( "Recovering up to: " + lastPossiblyApplying );
submitApplyJob( lastPossiblyApplying );
applier.sync( false );
}
}
@Override
public synchronized void stop() throws Throwable
{
applier.sync( true );
flush();
}
public synchronized CoreSnapshot snapshot() throws IOException, InterruptedException
{
applier.sync( false );
long prevIndex = lastApplied;
long prevTerm = raftLog.readEntryTerm( prevIndex );
CoreSnapshot coreSnapshot = new CoreSnapshot( prevIndex, prevTerm );
coreStateMachines.addSnapshots( coreSnapshot );
sessionTracker.addSnapshots( coreSnapshot );
return coreSnapshot;
}
synchronized void installSnapshot( CoreSnapshot coreSnapshot )
{
coreStateMachines.installSnapshots( coreSnapshot );
long snapshotPrevIndex = coreSnapshot.prevIndex();
try
{
if ( snapshotPrevIndex > 1 )
{
raftLog.skip( snapshotPrevIndex, coreSnapshot.prevTerm() );
}
}
catch ( IOException e )
{
throw new RuntimeException( e );
}
this.lastApplied = this.lastFlushed = snapshotPrevIndex;
log.info( format( "Skipping lastApplied index forward to %d", snapshotPrevIndex ) );
sessionTracker.installSnapshots( coreSnapshot );
}
@Override
public void prune() throws IOException
{
compact();
}
}