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Gremlin giving stale response

Aman <amandeep.srivastava1996@...>
 

Hi,

I've built a service around JanusGraph to ingest/retrieve data. When I ingest a new edge, the same is not reflected on the gremlin endpoint of JG. However, ingested vertices count is updated correctly.

Here's what I'm doing:
1. Use API to create 2 new vertices
2. Use API to create a new edge
3. Hit gremlin API to get vertex count -> shows 2 correctly
4. Hit gremlin API to get edge count -> shows 0

When I restart gremlin server, I'm able to see correct edge count via gremlin API (i.e. 1 in above example). My hunch is that gremlin API is using a stale transaction somewhere, hence returning incorrect data.

I tried setting 2 values of g in empty-sample.groovy:
1. globals << [g: graph.traversal()] -> This seems to give the correct number of vertices and edges always, so no issues with this one.
2. globals << [g: graph.buildTransaction().readOnly().start().traversal()] -> This seems to be having the above mentioned inconsistency issue.

I want the gremlin API to be read-only so all ingestions happen via my custom built APIs (I validate a few things before persisting data). Had following questions:

1. Why does the second value of g cause inconsistent results only for edges? If it's continuing on the same transaction, shouldn't staleness disrupt vertex count results too?
2. How can I set g value such that traversals are always readOnly and every request starts a new transaction, ending it after response has been returned to the clients.

Would appreciate it if the group can provide inputs.

Regards,
Aman
hadoopmarc@...
 

Hi Aman,

Without saying that I understand everything of the JanusGraph behaviour that you describe, I can add the following:
  • when accessing the graph via JanusGraph server (what you call the gremlin API) every request is a transaction already (unless you use sessions). So, using buildTransaction for defining g in JanusGraph Server is counterintuitive and possibly enters untested territory.
  • Apache TinkerPop has the so-called ReadOnlyStrategy to realize the behaviour you want. Can you try that instead?
Best wishes,    Marc
Aman <amandeep.srivastava1996@...>
 

Hi Marc,

Using read-only strategy is a really good suggesion. Let me try that, thanks!

Regards,
Aman


On Tue, 15 Mar, 2022, 12:45 pm , <hadoopmarc@...> wrote:
Hi Aman,

Without saying that I understand everything of the JanusGraph behaviour that you describe, I can add the following:
  • when accessing the graph via JanusGraph server (what you call the gremlin API) every request is a transaction already (unless you use sessions). So, using buildTransaction for defining g in JanusGraph Server is counterintuitive and possibly enters untested territory.
  • Apache TinkerPop has the so-called ReadOnlyStrategy to realize the behaviour you want. Can you try that instead?
Best wishes,    Marc

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