ReferenceEdge Serialization error using JanusGraph

Question

I'm getting serialization errors when retrieving a list of edges from a remote JanusGraph server using Gremlin in a Java application (error message and configurations bellow).

This is the traversal that raises the error:

List<Edge> eList = g.E().toList();

Trying to get only one edge also raises an error:

Edge edge= g.E().next();

Nevertheless, when retrieving a vertex or a list of vertices, it works perfectly:

List<Vertex> vList = g.V().toList();

This is my remote-objects.yaml file:

hosts: [localhost]
port: 8182
serializer: { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0,
              config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}

This is the code to get the remote traversal:

PropertiesConfiguration conf = new PropertiesConfiguration(remote-objects.yaml);
cluster = Cluster.open(conf.getString("gremlin.remote.driver.clusterFile"));
client = cluster.connect();
g = AnonymousTraversalSource.traversal().withRemote(propFileName);

This is the serializers in my server configuration:

serializers:
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV3d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0, config: { serializeResultToString: true }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV3d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV3d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  # Older serialization versions for backwards compatibility:
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV1d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoLiteMessageSerializerV1d0, config: {ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV1d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { serializeResultToString: true }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerGremlinV2d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV2d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerGremlinV1d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV1d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistryV1d0] }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GraphSONMessageSerializerV1d0, config: { ioRegistries: [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV1d0, org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistryV1d0] }}

And this the error message:

java.util.concurrent.CompletionException: io.netty.handler.codec.DecoderException: org.apache.tinkerpop.gremlin.driver.ser.SerializationException: org.apache.tinkerpop.shaded.kryo.KryoException: java.lang.NegativeArraySizeException
Serialization trace:
id (org.apache.tinkerpop.gremlin.structure.util.reference.ReferenceEdge)
    at java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:375)
CompletableFuture.java:375
    at java.util.concurrent.CompletableFuture.join(CompletableFuture.java:1934)
CompletableFuture.java:1934
    at org.apache.tinkerpop.gremlin.driver.ResultSet.one(ResultSet.java:119)
ResultSet.java:119
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.hasNext(ResultSet.java:171)
ResultSet.java:171
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:178)
ResultSet.java:178
    at org.apache.tinkerpop.gremlin.driver.ResultSet$1.next(ResultSet.java:165)
ResultSet.java:165
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:140)
DriverRemoteTraversal.java:140
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal$TraverserIterator.next(DriverRemoteTraversal.java:125)
DriverRemoteTraversal.java:125
    at org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteTraversal.nextTraverser(DriverRemoteTraversal.java:106)
DriverRemoteTraversal.java:106
    at org.apache.tinkerpop.gremlin.process.remote.traversal.step.map.RemoteStep.processNextStart(RemoteStep.java:80)
RemoteStep.java:80
    at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:128)
AbstractStep.java:128
    at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:38)
AbstractStep.java:38
    at org.apache.tinkerpop.gremlin.process.traversal.Traversal.fill(Traversal.java:179)
Traversal.java:179
    at org.apache.tinkerpop.gremlin.process.traversal.Traversal.toList(Traversal.java:117)
Traversal.java:117
    at com.ibm.graph.App.main(App.java:25)
App.java:25
Caused by: io.netty.handler.codec.DecoderException: org.apache.tinkerpop.gremlin.driver.ser.SerializationException: org.apache.tinkerpop.shaded.kryo.KryoException: java.lang.NegativeArraySizeException

Answer 1

I believe that your problem is in a mismatch of serializer configuration between driver and server. For the driver you do:

serializer: { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0,
              config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}

but for the server you have:

- { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV3d0, 
    config: { ioRegistries [org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerIoRegistryV3d0, 
                            org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}

You've omitted TinkerIoRegistryV3d0 on the driver side. With ioRegistries the order in which the registries are added matters. So, you might have gotten lucky if you'd added JanusGraphIoRegistry first on the server and then accidentally omitted TinkerIoRegistryV3d0 on the driver because the serializer registration identifiers would have aligned for JansuGraph.

Anyway, add TinkerIoRegistryV3d0 to the driver configuration OR remove it from the server configuration and things should work. As a side note, you typically only need the TinkerIoRegistryV3d0 if you're serializing TinkerGraph instances over the wire (e.g. using subgraph() step).