Questions about implementing and deploying custom traversal extensions
Hello,
I’m currently working on a project that has been using Neo4j, and we’re exploring migrating to JanusGraph (which uses tinkerpop). The main challenge we’re facing relates to how we currently use Neo4j: we’ve developed several stored procedures, including a custom traversal procedure (a recursive function that decides which path to traverse based on edge properties).
From what I’ve gathered so far, it seems that a similar feature could be implemented in Tinkerpop by extending the DSL and deploying it as a JAR into the extensions directory. However, I’m not completely sure if this is the best approach.
Our key requirements are performance-related — this traversal processes a large number of nodes and edges, and it should return complete paths. Therefore, it’s important for us to execute it server-side rather than client-side.
I created a proof of concept for the extension, but I’ve encountered issues during deployment. I placed the JAR file in the /opt/janusgraph/ext directory and added it to plugins.txt. However, when running the Gremlin console, I get the following error:
Could you please help clarify the following points?
Is extending the DSL the recommended approach for implementing a custom traversal?
If so, is the deployment method I described (placing the JAR in /opt/janusgraph/ext and declaring it in plugins.txt) correct?
How can I debug the above error? Could it be related to an incomplete plugin JAR? If possible, could you share an example of a working extension that I could use as a reference?
Thank you in advance for your help and any insights you can provide.
Best regards,
Michael
I’m currently working on a project that has been using Neo4j, and we’re exploring migrating to JanusGraph (which uses tinkerpop). The main challenge we’re facing relates to how we currently use Neo4j: we’ve developed several stored procedures, including a custom traversal procedure (a recursive function that decides which path to traverse based on edge properties).
From what I’ve gathered so far, it seems that a similar feature could be implemented in Tinkerpop by extending the DSL and deploying it as a JAR into the extensions directory. However, I’m not completely sure if this is the best approach.
Our key requirements are performance-related — this traversal processes a large number of nodes and edges, and it should return complete paths. Therefore, it’s important for us to execute it server-side rather than client-side.
I created a proof of concept for the extension, but I’ve encountered issues during deployment. I placed the JAR file in the /opt/janusgraph/ext directory and added it to plugins.txt. However, when running the Gremlin console, I get the following error:
Exception in thread "main" java.lang.NullPointerException: Cannot invoke method activate() on null object
at org.codehaus.groovy.runtime.NullObject.invokeMethod(NullObject.java:113)Could you please help clarify the following points?
Is extending the DSL the recommended approach for implementing a custom traversal?
If so, is the deployment method I described (placing the JAR in /opt/janusgraph/ext and declaring it in plugins.txt) correct?
How can I debug the above error? Could it be related to an incomplete plugin JAR? If possible, could you share an example of a working extension that I could use as a reference?
Thank you in advance for your help and any insights you can provide.
Best regards,
Michael
Apache TinkerPop is an open source graph computing framework and the home of the Gremlin graph query language.
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