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DatabaseHealth.java
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DatabaseHealth.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 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.internal;
import org.neo4j.graphdb.event.ErrorState;
import org.neo4j.helpers.Exceptions;
import org.neo4j.kernel.impl.core.DatabasePanicEventGenerator;
import org.neo4j.logging.Log;
import static org.neo4j.helpers.Exceptions.withCause;
public class DatabaseHealth
{
private static final String panicMessage = "Database has encountered some problem, "
+ "please perform necessary action (tx recovery/restart)";
private static final Class<?>[] CRITICAL_EXCEPTIONS = new Class[]{OutOfMemoryError.class};
private volatile boolean healthy = true;
private final DatabasePanicEventGenerator dbpe;
private final Log log;
private Throwable causeOfPanic;
public DatabaseHealth( DatabasePanicEventGenerator dbpe, Log log )
{
this.dbpe = dbpe;
this.log = log;
}
/**
* Asserts that the database is in good health. If that is not the case then the cause of the
* unhealthy state is wrapped in an exception of the given type, i.e. the panic disguise.
*
* @param panicDisguise the cause of the unhealthy state wrapped in an exception of this type.
* @throws EXCEPTION exception type to wrap cause in.
*/
public <EXCEPTION extends Throwable> void assertHealthy( Class<EXCEPTION> panicDisguise ) throws EXCEPTION
{
if ( !healthy )
{
EXCEPTION exception;
try
{
try
{
exception = panicDisguise.getConstructor( String.class, Throwable.class )
.newInstance( panicMessage, causeOfPanic );
}
catch ( NoSuchMethodException e )
{
exception = withCause( panicDisguise.getConstructor( String.class )
.newInstance( panicMessage ), causeOfPanic );
}
}
catch ( Exception e )
{
throw new Error( panicMessage + ". An exception of type " + panicDisguise.getName() +
" was requested to be thrown but that proved impossible", e );
}
throw exception;
}
}
public void panic( Throwable cause )
{
if ( !healthy )
{
return;
}
if ( cause == null )
{
throw new IllegalArgumentException( "Must provide a cause for the database panic" );
}
this.causeOfPanic = cause;
this.healthy = false;
log.error( "Database panic: " + panicMessage, cause );
dbpe.generateEvent( ErrorState.TX_MANAGER_NOT_OK, causeOfPanic );
}
public boolean isHealthy()
{
return healthy;
}
public boolean healed()
{
if ( hasCriticalFailure() )
{
log.error( "Database encountered a critical error and can't be healed. Restart required." );
return false;
}
else
{
healthy = true;
causeOfPanic = null;
log.info( "Database health set to OK" );
return true;
}
}
private boolean hasCriticalFailure()
{
return !isHealthy() && Exceptions.contains( causeOfPanic, CRITICAL_EXCEPTIONS );
}
public Throwable cause()
{
return causeOfPanic;
}
}