Neo4j service not starting - neo4j

Question

I have been using Neo4j for more than 3 months on this server. Not sure what changed, but today morning I am unable to start Neo4j server.
Till today everything was fine and there were not changes that I know of were made to Neo4j or anything else.
I am currently using neo4j 3.1.0.
The following is the error log.
xxx#dataserver:~$ sudo neo4j console
Starting Neo4j.
WARNING: Max 1024 open files allowed, minimum of 40000 recommended. See the Neo4j manual.
2017-05-01 03:09:17.948+0000 INFO Starting...
2017-05-01 03:09:18.616+0000 INFO Bolt enabled on 0.0.0.0:7687.
2017-05-01 03:09:20.766+0000 ERROR Failed to start Neo4j: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2241b683' was successfully initialized, but failed to start. Please see attached cause exception. Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2241b683' was successfully initialized, but failed to start. Please see attached cause exception.
org.neo4j.server.ServerStartupException: Starting Neo4j failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2241b683' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.server.exception.ServerStartupErrors.translateToServerStartupError(ServerStartupErrors.java:68)
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:227)
at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:91)
at org.neo4j.server.ServerBootstrapper.start(ServerBootstrapper.java:68)
at org.neo4j.server.CommunityEntryPoint.main(CommunityEntryPoint.java:28)
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2241b683' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:443)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:107)
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:199)
... 3 more
Caused by: java.lang.RuntimeException: Error starting org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory, /var/lib/neo4j/data/databases/default.graphdb
at org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory.initFacade(GraphDatabaseFacadeFactory.java:193)
at org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory.newFacade(GraphDatabaseFacadeFactory.java:124)
at org.neo4j.server.CommunityNeoServer.lambda$static$0(CommunityNeoServer.java:57)
at org.neo4j.server.database.LifecycleManagingDatabase.start(LifecycleManagingDatabase.java:89)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:433)
... 5 more
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.kernel.recovery.Recovery#4b1ec7fa' failed to initialize. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.init(LifeSupport.java:415)
at org.neo4j.kernel.lifecycle.LifeSupport.init(LifeSupport.java:62)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:98)
at org.neo4j.kernel.NeoStoreDataSource.start(NeoStoreDataSource.java:517)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:433)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:107)
at org.neo4j.kernel.impl.transaction.state.DataSourceManager.start(DataSourceManager.java:100)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:433)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:107)
at org.neo4j.kernel.impl.factory.GraphDatabaseFacadeFactory.initFacade(GraphDatabaseFacadeFactory.java:189)
... 9 more
Caused by: java.lang.IllegalArgumentException: Unknown entry type -1 for version -1. At position LogPosition{logVersion=94, byteOffset=157773910} and entry version V2_1
at org.neo4j.kernel.impl.transaction.log.entry.LogEntryVersion.entryParser(LogEntryVersion.java:141)
at org.neo4j.kernel.impl.transaction.log.entry.VersionAwareLogEntryReader.readLogEntry(VersionAwareLogEntryReader.java:84)
at org.neo4j.kernel.impl.transaction.log.LogEntryCursor.next(LogEntryCursor.java:54)
at org.neo4j.kernel.recovery.LatestCheckPointFinder.find(LatestCheckPointFinder.java:78)
at org.neo4j.kernel.recovery.PositionToRecoverFrom.apply(PositionToRecoverFrom.java:53)
at org.neo4j.kernel.recovery.DefaultRecoverySPI.getPositionToRecoverFrom(DefaultRecoverySPI.java:80)
at org.neo4j.kernel.recovery.Recovery.init(Recovery.java:80)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.init(LifeSupport.java:405)
... 18 more

Answer 1

Stop service
Change dbms.allow_upgrade to true in neo4j config file
Start service again
I had the same problem, and upgrading the db fixed it. I would also suggest changing the password if you are still using default password. Once you start the service it should upgrade the database, once upgraded, you can change the dbms.allow_upgrade to false again if you dont want neo4j to update automatically.