Hello,

I am using Janus 0.4.0 with Cassandra DB 3.11.4 (data getting replicated within 2 nodes) as backend storage.

While executing some queries I am getting following exception:

Caused by: java.lang.NullPointerException: Could not find type for id: 784405

at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:923) ~[guava-28.2-jre.jar:?]

at org.janusgraph.graphdb.types.vertices.JanusGraphSchemaVertex.name(JanusGraphSchemaVertex.java:57) ~[janusgraph-core-0.4.0.jar:?]

at org.janusgraph.graphdb.query.vertex.BasicVertexCentricQueryBuilder.constructQueryWithoutProfile(BasicVertexCentricQueryBuilder.java:497) ~[janusgraph-core-0.4.0.jar:?]

at org.janusgraph.graphdb.query.vertex.BasicVertexCentricQueryBuilder.constructQuery(BasicVertexCentricQueryBuilder.java:411) ~[janusgraph-core-0.4.0.jar:?]

at org.janusgraph.graphdb.query.vertex.VertexCentricQueryBuilder.execute(VertexCentricQueryBuilder.java:68) ~[janusgraph-core-0.4.0.jar:?]

at org.janusgraph.graphdb.query.vertex.VertexCentricQueryBuilder.vertices(VertexCentricQueryBuilder.java:114) ~[janusgraph-core-0.4.0.jar:?]

at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphVertexStep.flatMap(JanusGraphVertexStep.java:197) ~[janusgraph-core-0.4.0.jar:?]

at org.apache.tinkerpop.gremlin.process.traversal.step.map.FlatMapStep.processNextStart(FlatMapStep.java:49) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.janusgraph.graphdb.tinkerpop.optimize.JanusGraphVertexStep.processNextStart(JanusGraphVertexStep.java:182) ~[janusgraph-core-0.4.0.jar:?]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.next(ExpandableStepIterator.java:50) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.filter.FilterStep.processNextStart(FilterStep.java:37) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:143) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator.hasNext(ExpandableStepIterator.java:42) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep.processAllStarts(ReducingBarrierStep.java:82) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep.processNextStart(ReducingBarrierStep.java:112) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:128) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:38) ~[gremlin-core-3.4.1.jar:3.4.1]

at org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.next(DefaultTraversal.java:200) ~[gremlin-core-3.4.1.jar:3.4.1]

The queries are for which this issue  exception is reported are simple queries-

e.g. 

g.V().has("type", "employee").out("worksfor", "reportsto").has("deptName", P.within("HR", "IT"))

I  am suspecting this is something internal to JanusGraph or Cassandra.  But not getting exact reason behind this. 

After restarting services accessing JanusGraph this issue disappears. Tried to reproduce this issue again but no luck. I didn't found any help on above exception.

Any idea on what kind of exception is this ? What can be possible reasons for it ?

Thanks,

Sushant