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PersistentSnapshotDownloader.java
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PersistentSnapshotDownloader.java
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/*
* Copyright (c) 2002-2017 "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.core.state.snapshot;
import java.util.concurrent.TimeUnit;
import org.neo4j.causalclustering.catchup.storecopy.StoreCopyFailedException;
import org.neo4j.causalclustering.core.consensus.LeaderLocator;
import org.neo4j.causalclustering.core.consensus.NoLeaderFoundException;
import org.neo4j.causalclustering.core.state.CommandApplicationProcess;
import org.neo4j.causalclustering.helper.ExponentialBackoffStrategy;
import org.neo4j.causalclustering.helper.TimeoutStrategy;
import org.neo4j.logging.Log;
class PersistentSnapshotDownloader implements Runnable
{
static final String OPERATION_NAME = "download of snapshot";
private final CommandApplicationProcess applicationProcess;
private final LeaderLocator leaderLocator;
private final CoreStateDownloader downloader;
private final Log log;
private final TimeoutStrategy.Timeout timeout;
private State state;
PersistentSnapshotDownloader( LeaderLocator leaderLocator,
CommandApplicationProcess applicationProcess, CoreStateDownloader downloader, Log log,
TimeoutStrategy.Timeout timeout )
{
this.applicationProcess = applicationProcess;
this.leaderLocator = leaderLocator;
this.downloader = downloader;
this.log = log;
this.timeout = timeout;
this.state = State.INITIATED;
}
PersistentSnapshotDownloader( LeaderLocator leaderLocator,
CommandApplicationProcess applicationProcess, CoreStateDownloader downloader, Log log )
{
this( leaderLocator, applicationProcess, downloader, log,
new ExponentialBackoffStrategy( 1, 30, TimeUnit.SECONDS ).newTimeout() );
}
private enum State
{
INITIATED,
RUNNING,
STOPPED,
COMPLETED
}
@Override
public void run()
{
if ( !initialStateOk() )
{
return;
}
try
{
state = State.RUNNING;
applicationProcess.pauseApplier( OPERATION_NAME );
while ( state == State.RUNNING )
{
try
{
downloader.downloadSnapshot( leaderLocator.getLeader() );
break;
}
catch ( StoreCopyFailedException e )
{
log.error( "Failed to download snapshot. Retrying in {} ms.", timeout.getMillis(), e );
}
catch ( NoLeaderFoundException e )
{
log.warn( "No leader found. Retrying in {} ms.", timeout.getMillis() );
}
Thread.sleep( timeout.getMillis() );
timeout.increment();
}
}
catch ( InterruptedException e )
{
log.error( "Persistent snapshot downloader was interrupted" );
}
finally
{
applicationProcess.resumeApplier( OPERATION_NAME );
state = State.COMPLETED;
}
}
private boolean initialStateOk()
{
switch ( state )
{
case INITIATED:
return true;
case RUNNING:
log.error( "Persistent snapshot downloader is already running. " +
"Illegal state '{}'. Expected '{}'", state, State.INITIATED );
return false;
case STOPPED:
log.info( "Persistent snapshot downloader was stopped before starting" );
return false;
case COMPLETED:
log.error( "Persistent snapshot downloader has already completed. " +
"Illegal state '{}'. Expected '{}'", state, State.INITIATED );
return false;
default:
log.error( "Not a recognised state. " +
"Illegal state '{}'. Expected '{}'", state, State.INITIATED );
return false;
}
}
void stop()
{
if ( state == State.RUNNING )
{
state = State.STOPPED;
}
else if ( state == State.INITIATED )
{
state = State.COMPLETED;
}
}
boolean isRunning()
{
return state == State.RUNNING;
}
boolean hasCompleted()
{
return state == State.COMPLETED;
}
}