Neo4j群集-Neo4j节点启动时“ UnableToSampleException”，该节点在崩溃之前是主节点

Question

I have cluster of 3 neo4j databases. Node1 - master. Node2 - slave. Node3 - slave.

Node1 crashes for some reason. After short time cluster detects that and elect new master. So, now we have: Node1 - ? Node2 - master Node3 - slave

When I boot up Node1, it:

• Joins cluster
• Then gets new database version from master (store, than log files)
• Then it stucks at org.neo4j.server.rrd.UnableToSampleException error.

Stacktrace:

org.neo4j.server.rrd.UnableToSampleException
    at org.neo4j.server.rrd.sampler.NodeIdsInUseSampleable.getValue(NodeIdsInUseSampleable.java:47)
    at org.neo4j.server.rrd.RrdSamplerImpl.updateSample(RrdSamplerImpl.java:59)
    at org.neo4j.server.rrd.RrdJob.run(RrdJob.java:43)
    at org.neo4j.server.rrd.ScheduledJob$1.run(ScheduledJob.java:41)
    at java.util.TimerThread.mainLoop(Timer.java:555)
    at java.util.TimerThread.run(Timer.java:505)

Logs:

2014-11-13 12:11:50.147+0000 INFO  [Cluster] Checking store consistency with master
2014-11-13 12:11:50.853+0000 INFO  [Cluster] The store is inconsistent. Will treat it as branched and fetch a new one from the master
2014-11-13 12:11:52.030+0000 INFO  [Cluster] Copying store from master
... copying store
... copying schema
... copying logs
2014-11-13 12:13:57.768+0000 INFO  [API] Server started on: http://0.0.0.0:7474/
// it starts server, while logs download is in progress
... org.neo4j.server.rrd.UnableToSampleException error loop

---

• Sometimes error loop stops after some time (10-15 min) and server starts normally.
• If I restart neo4j again, everything works normally.

Any ideas, what this can be?

Answer 1

The root exception is not being logged. You have to debug the NodeIdsInUseSampleable class. In my case i got the following exception:

java.lang.IllegalStateException: XaDataSourceManager has been shut down.
    at org.neo4j.kernel.impl.transaction.XaDataSourceManager.getXaDataSource(XaDataSourceManager.java:211)
    at org.neo4j.kernel.impl.transaction.XaDataSourceManager.getNeoStoreDataSource(XaDataSourceManager.java:225)
    at org.neo4j.kernel.impl.nioneo.xa.NioNeoDbPersistenceSource.getNumberOfIdsInUse(NioNeoDbPersistenceSource.java:72)
    at org.neo4j.kernel.impl.core.NodeManager.getNumberOfIdsInUse(NodeManager.java:689)
    at org.neo4j.server.rrd.sampler.NodeIdsInUseSampleable.getValue(NodeIdsInUseSampleable.java:43)
    at org.neo4j.server.rrd.RrdSamplerImpl.updateSample(RrdSamplerImpl.java:59)
    at org.neo4j.server.rrd.RrdJob.run(RrdJob.java:43)
    at org.neo4j.server.rrd.ScheduledJob$1.run(ScheduledJob.java:41)
    at java.util.TimerThread.mainLoop(Timer.java:555)
    at java.util.TimerThread.run(Timer.java:505)

In my case the exception occurred since shutdown was invoked. I assume this might be the same for you. You just have to determine who is calling shutdown.