Neo4j embedded online backup from Java - scala

Question

I am using Neo4j(embedded) Enterprise edition 1.9.4 along with Scala-Neo4j wrapper in my project. I tried to backup the Neo4j data using Java like below
def backup_data()
{
val backupPath: File = new File("D:/neo4j-enterprise-1.9.4/data/backup/")
val backup = OnlineBackup.from( "127.0.0.1" )
if(backupPath.list().length > 0)
{
backup.incremental( backupPath.getPath() )
}
else
{
backup.full( backupPath.getPath() );
}
}
It is working fine for the full backup. But the incremental backup part is throwing the Null pointer exception.
Where did I go wrong?
EDIT
Building the GraphDatabase instance through Scala-Neo4j wrapper
class MyNeo4jClass extends SomethingClass with Neo4jWrapper with EmbeddedGraphDatabaseServiceProvider {
def neo4jStoreDir = "/tmp/temp-neo-test"
. . .
}
Stacktrace
Exception in thread "main" java.lang.NullPointerException
at org.neo4j.consistency.checking.OwnerChain$3.checkReference(OwnerChain.java:111)
at org.neo4j.consistency.checking.OwnerChain$3.checkReference(OwnerChain.java:106)
at org.neo4j.consistency.report.ConsistencyReporter$DiffReportHandler.checkReference(ConsistencyReporter.java:330)
at org.neo4j.consistency.report.ConsistencyReporter.dispatchReference(ConsistencyReporter.java:109)
at org.neo4j.consistency.report.PendingReferenceCheck.checkReference(PendingReferenceCheck.java:50)
at org.neo4j.consistency.store.DirectRecordReference.dispatch(DirectRecordReference.java:39)
at org.neo4j.consistency.report.ConsistencyReporter$ReportInvocationHandler.forReference(ConsistencyReporter.java:236)
at org.neo4j.consistency.report.ConsistencyReporter$ReportInvocationHandler.dispatchForReference(ConsistencyReporter.java:228)
at org.neo4j.consistency.report.ConsistencyReporter$ReportInvocationHandler.invoke(ConsistencyReporter.java:192)
at $Proxy17.forReference(Unknown Source)
at org.neo4j.consistency.checking.OwnerChain.check(OwnerChain.java:143)
at org.neo4j.consistency.checking.PropertyRecordCheck.checkChange(PropertyRecordCheck.java:57)
at org.neo4j.consistency.checking.PropertyRecordCheck.checkChange(PropertyRecordCheck.java:35)
at org.neo4j.consistency.report.ConsistencyReporter.dispatchChange(ConsistencyReporter.java:101)
at org.neo4j.consistency.report.ConsistencyReporter.forPropertyChange(ConsistencyReporter.java:382)
at org.neo4j.consistency.checking.incremental.StoreProcessor.checkProperty(StoreProcessor.java:61)
at org.neo4j.consistency.checking.AbstractStoreProcessor.processProperty(AbstractStoreProcessor.java:95)
at org.neo4j.consistency.store.DiffRecordStore$DispatchProcessor.processProperty(DiffRecordStore.java:207)
at org.neo4j.kernel.impl.nioneo.store.PropertyStore.accept(PropertyStore.java:83)
at org.neo4j.kernel.impl.nioneo.store.PropertyStore.accept(PropertyStore.java:43)
at org.neo4j.consistency.store.DiffRecordStore.accept(DiffRecordStore.java:159)
at org.neo4j.kernel.impl.nioneo.store.RecordStore$Processor.applyById(RecordStore.java:180)
at org.neo4j.consistency.store.DiffStore.apply(DiffStore.java:73)
at org.neo4j.kernel.impl.nioneo.store.StoreAccess.applyToAll(StoreAccess.java:174)
at org.neo4j.consistency.checking.incremental.IncrementalDiffCheck.execute(IncrementalDiffCheck.java:43)
at org.neo4j.consistency.checking.incremental.DiffCheck.check(DiffCheck.java:39)
at org.neo4j.consistency.checking.incremental.intercept.CheckingTransactionInterceptor.complete(CheckingTransactionInterceptor.java:160)
at org.neo4j.kernel.impl.transaction.xaframework.InterceptingXaLogicalLog$1.intercept(InterceptingXaLogicalLog.java:79)
at org.neo4j.kernel.impl.transaction.xaframework.XaLogicalLog$LogDeserializer.readAndWriteAndApplyEntry(XaLogicalLog.java:1120)
at org.neo4j.kernel.impl.transaction.xaframework.XaLogicalLog.applyTransaction(XaLogicalLog.java:1292)
at org.neo4j.kernel.impl.transaction.xaframework.XaResourceManager.applyCommittedTransaction(XaResourceManager.java:766)
at org.neo4j.kernel.impl.transaction.xaframework.XaDataSource.applyCommittedTransaction(XaDataSource.java:246)
at org.neo4j.com.ServerUtil.applyReceivedTransactions(ServerUtil.java:423)
at org.neo4j.backup.BackupService.unpackResponse(BackupService.java:453)
at org.neo4j.backup.BackupService.incrementalWithContext(BackupService.java:388)
at org.neo4j.backup.BackupService.doIncrementalBackup(BackupService.java:286)
at org.neo4j.backup.BackupService.doIncrementalBackup(BackupService.java:273)
at org.neo4j.backup.OnlineBackup.incremental(OnlineBackup.java:147)
at Saddahaq.User_node$.backup_data(User_node.scala:1637)
at Saddahaq.User_node$.main(User_node.scala:2461)
at Saddahaq.User_node.main(User_node.scala)

Answer 1

After the backup is taken, the backed target is checked for consistency. The incremental version of the consistency checker currently suffers from a bug leading to the observed NPE.
Workaround: either always take full backups with backup.full or prevent consistency checking on incremental backups by using
backup.incremental(backupPath.getPath(), false);