J
JanusGraph•12mo ago
rpuga

Unable to use next() in gremlin-python

Hi, has anyone tried to use gremlin-python with janusgraph 1.0.0? It seems that there is a bug that makes next() unusable. Here is an example of how to reproduce the issue: 
# Python 3.10.12
# janusgraph 1.0.0
# gremlinpython==3.7.0

from gremlin_python.process.anonymous_traversal import traversal
from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection

connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g")
g = traversal().withRemote(connection)

g.V().drop().iterate()
g.E().drop().iterate()
v1 = g.addV('vertex').property('name', 'v1').next()
# Python 3.10.12
# janusgraph 1.0.0
# gremlinpython==3.7.0

from gremlin_python.process.anonymous_traversal import traversal
from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection

connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g")
g = traversal().withRemote(connection)

g.V().drop().iterate()
g.E().drop().iterate()
v1 = g.addV('vertex').property('name', 'v1').next()
This generates a KeyError: 
[...]

~/.local/lib/python3.10/site-packages/gremlin_python/structure/io/graphbinaryV1.py in read_object(self, b)
    192             return self.to_object(io.BytesIO(b))
    193         elif isinstance(b, io.BufferedIOBase):
--> 194             return self.to_object(b)
    195 
    196     def to_object(self, buff, data_type=None, nullable=True):

~/.local/lib/python3.10/site-packages/gremlin_python/structure/io/graphbinaryV1.py in to_object(self, buff, data_type, nullable)
    201                     buff.read(1)
    202                 return None
--> 203             return self.deserializers[DataType(bt)].objectify(buff, self, nullable)
    204         else:
    205             return self.deserializers[data_type].objectify(buff, self, nullable)

KeyError: <DataType.custom: 0>
[...]

~/.local/lib/python3.10/site-packages/gremlin_python/structure/io/graphbinaryV1.py in read_object(self, b)
    192             return self.to_object(io.BytesIO(b))
    193         elif isinstance(b, io.BufferedIOBase):
--> 194             return self.to_object(b)
    195 
    196     def to_object(self, buff, data_type=None, nullable=True):

~/.local/lib/python3.10/site-packages/gremlin_python/structure/io/graphbinaryV1.py in to_object(self, buff, data_type, nullable)
    201                     buff.read(1)
    202                 return None
--> 203             return self.deserializers[DataType(bt)].objectify(buff, self, nullable)
    204         else:
    205             return self.deserializers[data_type].objectify(buff, self, nullable)

KeyError: <DataType.custom: 0>
Using g.addV('vertex').property('name', 'v1').iterate() instead of next() works fine. Any thoughts?
Solution:
This is my config https://github.com/Citegraph/citegraph/blob/main/backend/src/main/resources/gremlin-server-cql.yaml. I just tested python driver and java driver and they both worked well.
Jump to solution
10 Replies
rpuga
rpuga•12mo ago
Also, g.V().count().next() works, but g.V().next() yields the same KeyError
Bo
Bo•12mo ago
Try using GraphSONMessageSerializerV3 in your server config, e.g. { className: org.apache.tinkerpop.gremlin.util.ser.GraphSONMessageSerializerV3, config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }}
rpuga
rpuga•12mo ago
Thanks for the suggestion. Unfortunately, after setting the serializer to GraphSONMessageSerializerV3 I get the following error 😦 
GremlinServerError: 599: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
GremlinServerError: 599: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
Bo
Bo•12mo ago
Did you include config: { ioRegistries: [org.janusgraph.graphdb.tinkerpop.JanusGraphIoRegistry] }? If you are still facing the error, could you please share your server config yaml file?
rpuga
rpuga•12mo ago
Hi, yes, here is the yaml file is attached. And here is the error: 
[...]
  File "/var/lib/janusgraph/.local/lib/python3.10/site-packages/gremlin_python/driver/connection.py", line 90, in _receive
    status_code = self._protocol.data_received(data, self._results)
  File "/var/lib/janusgraph/.local/lib/python3.10/site-packages/gremlin_python/driver/protocol.py", line 138, in data_received
    raise GremlinServerError(message['status'])
gremlin_python.driver.protocol.GremlinServerError: 599: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
[...]
  File "/var/lib/janusgraph/.local/lib/python3.10/site-packages/gremlin_python/driver/connection.py", line 90, in _receive
    status_code = self._protocol.data_received(data, self._results)
  File "/var/lib/janusgraph/.local/lib/python3.10/site-packages/gremlin_python/driver/protocol.py", line 138, in data_received
    raise GremlinServerError(message['status'])
gremlin_python.driver.protocol.GremlinServerError: 599: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
BTW: When I enable the GraphSONMessageSerializerV3 serializer in the yaml config file, I also get the same error from a Java app that connects to JanusGraph (my Java app works fine with the default serializer): 
java.util.concurrent.CompletionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
        at java.base/java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:412)
        at java.base/java.util.concurrent.CompletableFuture.join(CompletableFuture.java:2044)
        at org.apache.tinkerpop.gremlin.driver.ResultSet.one(ResultSet.java:123)
        at org.apache.tinkerpop.gremlin.driver.ResultSet$1.hasNext(ResultSet.java:175)
        at com.example.GremlinJavaExample.main(GremlinJavaExample.java:49) 
java.util.concurrent.CompletionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: Error during serialization: Serializer for type org.janusgraph.graphdb.relations.RelationIdentifier not found
        at java.base/java.util.concurrent.CompletableFuture.reportJoin(CompletableFuture.java:412)
        at java.base/java.util.concurrent.CompletableFuture.join(CompletableFuture.java:2044)
        at org.apache.tinkerpop.gremlin.driver.ResultSet.one(ResultSet.java:123)
        at org.apache.tinkerpop.gremlin.driver.ResultSet$1.hasNext(ResultSet.java:175)
        at com.example.GremlinJavaExample.main(GremlinJavaExample.java:49)

janusgraph-server.ya...

Solution
Bo
Bo•12mo ago
This is my config https://github.com/Citegraph/citegraph/blob/main/backend/src/main/resources/gremlin-server-cql.yaml. I just tested python driver and java driver and they both worked well.
Bo
Bo•12mo ago
In your java driver case, when you built 
Cluster cluster = Cluster.build("localhost")
  .port(8182)
  .serializer(createGraphBinaryMessageSerializerV1())
  .create();

private MessageSerializer createGraphBinaryMessageSerializerV1() {
  final GraphBinaryMessageSerializerV1 serializer = new GraphBinaryMessageSerializerV1();
  final Map<String, Object> config = new HashMap<>();
  config.put(TOKEN_IO_REGISTRIES, Collections.singletonList(JanusGraphIoRegistry.class.getName()));
  serializer.configure(config, Collections.emptyMap());
  return serializer;
}
Cluster cluster = Cluster.build("localhost")
  .port(8182)
  .serializer(createGraphBinaryMessageSerializerV1())
  .create();

private MessageSerializer createGraphBinaryMessageSerializerV1() {
  final GraphBinaryMessageSerializerV1 serializer = new GraphBinaryMessageSerializerV1();
  final Map<String, Object> config = new HashMap<>();
  config.put(TOKEN_IO_REGISTRIES, Collections.singletonList(JanusGraphIoRegistry.class.getName()));
  serializer.configure(config, Collections.emptyMap());
  return serializer;
}
Make sure it includes the serializer that your server is using. In the above example, it would only work if your server enables GraphBinaryMessageSerializerV1
rpuga
rpuga•12mo ago
Thank you for the examples, they are very useful! I used your .yaml file, and now gremlin-python works. Earlier, I forgot to specify the serializer. I added the following and now it works OK: 
message_serializer = serializer.GraphSONSerializersV3d0()
connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g", message_serializer=message_serializer)
message_serializer = serializer.GraphSONSerializersV3d0()
connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g", message_serializer=message_serializer)
I'll try your solution for the Java code as well. Thanks! Update: the Java solution also worked, thank you very much!
Bo
Bo•12mo ago
message_serializer = serializer.GraphSONSerializersV3d0()
connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g", message_serializer=message_serializer)
message_serializer = serializer.GraphSONSerializersV3d0()
connection = DriverRemoteConnection("ws://jgserver:8182/gremlin", "g", message_serializer=message_serializer)
Interesting though, coz I didn't have to specify the message serializer when using python. I thought the python driver would somehow figure it out by itself.
cdegroc
cdegroc•12mo ago
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