janusgraph-users@lists.lfaidata.foundation | Error when trying to read ElementMap from Edge in Gremlin.Net: The given key 'janusgraph.RelationIdentifier' was not present in the dictionary

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Error when trying to read ElementMap from Edge in Gremlin.Net: The given key 'janusgraph.RelationIdentifier' was not present in the dictionary

#gremlin-dotnet

Florian Hockmann

A better exception would really be a good idea. This is however an issue in TinkerPop and not JanusGraph as the Gremlin.Net driver belongs to TinkerPop.

I went ahead and created an issue for this in the TinkerPop project: https://issues.apache.org/jira/browse/TINKERPOP-2853

Registration for this Jira instance is closed unfortunately due to problems with spam so you would have to ask for an account to be created which is why I thought that it might be to easier if I just go ahead and create the issue myself.

But you can of course create a PR to improve this if you want. The repository is: https://github.com/apache/tinkerpop

Von: janusgraph-users@... <janusgraph-users@...> Im Auftrag von tormodhau@...
Gesendet: Dienstag, 10. Januar 2023 08:18
An: janusgraph-users@...
Betreff: Re: [janusgraph-users] Error when trying to read ElementMap from Edge in Gremlin.Net: The given key 'janusgraph.RelationIdentifier' was not present in the dictionary #gremlin-dotnet

Hi, Florian!

Thank you so much! I have found this repository during my research, but I didn't understand why it was needed at the time. It makes total sense now.

Now, the exception thrown might seem a little confusing. Do you think it would be viable to catch the KeyNotFoundException inside. TypeSerializerRegistry (or similar), and then give a better explanation? An exception saying e.g "Serializer for type ''janusgraph..xx' was not found. See documentation on custom serializers [...]" would be much more telling on where to look.

Would you like me to add this as an issue in the Janusgraph repo?

tormodhau@...

#6675

Would you like me to add this as an issue in the Janusgraph repo?

Florian Hockmann

#6674

Hi,

`RelationIdentifier` is a type specific to JanusGraph which is why Gremlin.Net cannot know how to deserialize it. We have built a library that extends Gremlin.Net with JanusGraph specific types to solve this: https://github.com/JanusGraph/janusgraph-dotnet/

You can simply create a JanusGraphGraphSONMessageSerializer or a GraphBinaryMessageSerializer with the JanusGraphTypeSerializerRegistry.Instance and provide that to the constructor of GremlinClient.

Von: janusgraph-users@... <janusgraph-users@...> Im Auftrag von tormodhau@...
Gesendet: Montag, 9. Januar 2023 10:25
An: janusgraph-users@...
Betreff: [janusgraph-users] Error when trying to read ElementMap from Edge in Gremlin.Net: The given key 'janusgraph.RelationIdentifier' was not present in the dictionary #gremlin-dotnet

Hi!

When I try to read the ElementMap of an edge in Gremlin.Net:

var edgeValues = g.E()

.Has("Mrid", "..guid..")

.ElementMap<object>()

.Next(); // <---- Throws here

I get the following error:

System.Collections.Generic.KeyNotFoundException : The given key 'janusgraph.RelationIdentifier' was not present in the dictionary.

Environment:

JanusGraph, ElasticSearch, Cassandra (the official docker-compose running locally)
Gremlin.Net 3.6.1
Dotnet Core 6.4.0

Full example (unit test with xUnit):

[Fact]

public void AddingEdgeBetweenTwoVertexes()

{

// Start a Janusgraph + Cassandra + ElasticSearch environment with docker compose:

// https://github.com/JanusGraph/janusgraph-docker/blob/master/docker-compose-cql-es.yml

var gremlinServer = new GremlinServer("localhost", 8182);

var gremlinClient = new GremlinClient(gremlinServer);

var remoteConnection = new DriverRemoteConnection(gremlinClient, "g");

var g = AnonymousTraversalSource.Traversal().WithRemote(remoteConnection);

g.V().Drop().Iterate();

g.E().Drop().Iterate();

var firstMrid = Guid.NewGuid();

g.AddV("V1")

.Property("Mrid", firstMrid)

.Iterate();

var secondMrid = Guid.NewGuid();

g.AddV("V2")

.Property("Mrid", secondMrid)

.Iterate();

var edgeMrid = Guid.NewGuid();

g.AddE("E1")

.Property("Mrid", edgeMrid)

.Property("Name", "Hello Edge")

.From(__.V().Has("Mrid", firstMrid))

.To(__.V().Has("Mrid", secondMrid))

.Iterate();

// Verify that two vertices and one edge is added

Assert.Equal(1, g.E().Count().Next());

Assert.Equal(2, g.V().Count().Next());

var edgeValues = g.E()

.Has("Mrid", edgeMrid)

.ElementMap<object>()

.Next(); // <---- Throws here

Assert.Equal("Hello Edge", edgeValues["Name"]);

}

Full error:

[xUnit.net 00:00:02.06] tests.Graph.GremlinExplorationTest.AddingEdgeBetweenTwoVertexes_ [FAIL]

Failed tests.Graph.GremlinExplorationTest.AddingEdgeBetweenTwoVertexes_ [465 ms]

Error Message:

System.Collections.Generic.KeyNotFoundException : The given key 'janusgraph.RelationIdentifier' was not present in the dictionary.

Stack Trace:

at System.Collections.Generic.Dictionary`2.get_Item(TKey key)

at Gremlin.Net.Structure.IO.GraphBinary.TypeSerializerRegistry.GetSerializerForCustomType(String typeName)

at Gremlin.Net.Structure.IO.GraphBinary.GraphBinaryReader.ReadAsync(Stream stream)

at Gremlin.Net.Structure.IO.GraphBinary.Types.MapSerializer`2.ReadValueAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadValueAsync(Stream stream, GraphBinaryReader reader, Boolean nullable)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.GraphBinaryReader.ReadAsync(Stream stream)

at Gremlin.Net.Structure.IO.GraphBinary.Types.TraverserSerializer.ReadValueAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadValueAsync(Stream stream, GraphBinaryReader reader, Boolean nullable)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.GraphBinaryReader.ReadAsync(Stream stream)

at Gremlin.Net.Structure.IO.GraphBinary.Types.ListSerializer`1.ReadValueAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadValueAsync(Stream stream, GraphBinaryReader reader, Boolean nullable)

at Gremlin.Net.Structure.IO.GraphBinary.Types.SimpleTypeSerializer`1.ReadAsync(Stream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.GraphBinaryReader.ReadAsync(Stream stream)

at Gremlin.Net.Structure.IO.GraphBinary.ResponseMessageSerializer.ReadValueAsync(MemoryStream stream, GraphBinaryReader reader)

at Gremlin.Net.Structure.IO.GraphBinary.GraphBinaryMessageSerializer.DeserializeMessageAsync(Byte[] message)

at Gremlin.Net.Driver.Connection.HandleReceivedAsync(Byte[] received)

at Gremlin.Net.Driver.Connection.ReceiveMessagesAsync()

at Gremlin.Net.Driver.ProxyConnection.SubmitAsync[T](RequestMessage requestMessage)

at Gremlin.Net.Driver.GremlinClient.SubmitAsync[T](RequestMessage requestMessage)

at Gremlin.Net.Driver.Remote.DriverRemoteConnection.SubmitBytecodeAsync(Guid requestid, Bytecode bytecode)

at Gremlin.Net.Driver.Remote.DriverRemoteConnection.SubmitAsync[S,E](Bytecode bytecode)

at Gremlin.Net.Process.Remote.RemoteStrategy.ApplyAsync[S,E](ITraversal`2 traversal)

at Gremlin.Net.Process.Utils.WaitUnwrap(Task task)

at Gremlin.Net.Process.Remote.RemoteStrategy.Apply[S,E](ITraversal`2 traversal)

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.ApplyStrategies()

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.GetTraverserEnumerator()

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.get_TraverserEnumerator()

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.MoveNextInternal()

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.MoveNext()

at Gremlin.Net.Process.Traversal.DefaultTraversal`2.Next()

at tests.Graph.GremlinExplorationTest.AddingEdgeBetweenTwoVertexes_() in /Users/tormodhaugene/customers/volue/spark-grid/tests/Graph/GremlinExplorationTest.cs:line 130

at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)

at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)

Does anyone know what this error means or how to avoid it? I am at a loss on how to debug it.

- Tormod

tormodhau@...

#6673