Feature Request: OpenSearch v2 and v3 Support #4887
Description
Describe the feature
Add support for OpenSearch v2 and v3 as a mixed index backend.
Describe a specific use case for the feature
Use Case
JanusGraph currently supports Elasticsearch v7. OpenSearch v2 and v3 are API-compatible with ES v7, but JanusGraph's version check code rejects these OpenSearch versions.
Technical Context
JanusGraph's ES compatibility classes for v6, v7, v8, and v9 are essentially identical, indicating that JanusGraph doesn't rely on version-specific Elasticsearch features. See the compatibility layer implementation:
https://github.com/janusgraph/janusgraph/tree/master/janusgraph-es/src/main/java/org/janusgraph/diskstorage/es/compat
Related Discussion
There is an ongoing discussion about Vector Search support (#4839). Note that OpenSearch ML-Commons and Elasticsearch have different vector search implementations, which may require separate consideration.
Proposed Solution
Modify the version validation logic to accept OpenSearch v2.x and v3.x versions, leveraging the existing ES v7 compatibility layer.