neo4j - UnexpectedUpgradingStoreVersionException. File is version 'NodeStore v0.A.4' - neo4j

Question

Our neo4j server just crashed, and when I tried to call bin/neo4j start, I'm getting this error:
2015-04-21 07:50:49.529 ERROR Failed to start Neo Server on port [unknown port] Starting Neo4j Server failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2c651755' was successfully initialized, but failed to start. Please see attached cause exception.
org.neo4j.server.ServerStartupException: Starting Neo4j Server failed: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2c651755' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:244)
at org.neo4j.server.Bootstrapper.start(Bootstrapper.java:125)
at org.neo4j.server.Bootstrapper.main(Bootstrapper.java:68)
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.server.database.LifecycleManagingDatabase#2c651755' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:499)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:108)
at org.neo4j.server.AbstractNeoServer.start(AbstractNeoServer.java:192)
... 2 more
Caused by: java.lang.RuntimeException: Error starting org.neo4j.kernel.EmbeddedGraphDatabase, /var/lib/neo4j/hangwith.db
at org.neo4j.kernel.InternalAbstractGraphDatabase.run(InternalAbstractGraphDatabase.java:314)
at org.neo4j.kernel.EmbeddedGraphDatabase.<init>(EmbeddedGraphDatabase.java:59)
at org.neo4j.server.database.LifecycleManagingDatabase$1.newGraphDatabase(LifecycleManagingDatabase.java:43)
at org.neo4j.server.database.LifecycleManagingDatabase.start(LifecycleManagingDatabase.java:103)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:493)
... 4 more
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.kernel.impl.transaction.state.DataSourceManager#10c9f7b4' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:499)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:108)
at org.neo4j.kernel.InternalAbstractGraphDatabase.run(InternalAbstractGraphDatabase.java:309)
... 8 more
Caused by: org.neo4j.kernel.lifecycle.LifecycleException: Component 'org.neo4j.kernel.NeoStoreDataSource#138924b9' was successfully initialized, but failed to start. Please see attached cause exception.
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:499)
at org.neo4j.kernel.lifecycle.LifeSupport.start(LifeSupport.java:108)
at org.neo4j.kernel.impl.transaction.state.DataSourceManager.start(DataSourceManager.java:117)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:493)
... 10 more
Caused by: org.neo4j.kernel.impl.storemigration.StoreUpgrader$UnexpectedUpgradingStoreVersionException: 'neostore.nodestore.db' has a store version number that we cannot upgrade from. Expected 'v0.A.3' but file is version 'NodeStore v0.A.4'.
at org.neo4j.kernel.impl.storemigration.UpgradableDatabase.checkUpgradeable(UpgradableDatabase.java:88)
at org.neo4j.kernel.impl.storemigration.StoreMigrator.needsMigration(StoreMigrator.java:158)
at org.neo4j.kernel.impl.storemigration.StoreUpgrader.getParticipantsEagerToMigrate(StoreUpgrader.java:259)
at org.neo4j.kernel.impl.storemigration.StoreUpgrader.migrateIfNeeded(StoreUpgrader.java:134)
at org.neo4j.kernel.NeoStoreDataSource.upgradeStore(NeoStoreDataSource.java:532)
at org.neo4j.kernel.NeoStoreDataSource.start(NeoStoreDataSource.java:434)
at org.neo4j.kernel.lifecycle.LifeSupport$LifecycleInstance.start(LifeSupport.java:493)
... 13 more
The server lib were magically updated to 2.3.0-M01.
How do I fix this problem? Would downgrade to the older binary help me? If so, which binary supports NodeStore v0.A.4?

Answer 1

Seems like you have upgraded your Neo4j instance but it will not start since the database store files have not been upgraded. These require an explicit upgrade. What was the version of Neo4j you were running previously?
To upgrade your graph database explicitly you need to set
allow_store_upgrade=true
in \conf\neo4j.properties. Note that this line should be present in the file already but commented out with a #.
Bear in mind that 2.3.0-M1 is a milestone release and may not be stable. The latest stable version is 2.2.1.