Support for OpenSearch v3.

[tae898]

Hi,

I got OpenSearch v2.19.3 working (https://github.com/humemai/janusgraph/blob/40b5e0a808e6a62e85b379968d9470505f6bf588/janusgraph-dist/docker/examples/docker-compose-cql-es.yml) as a janusgraph.index.search.backend, but as you know since OpenSearch is not officially supported and also due to the nature of how OpenSearch initially started, currently we have to pretend that it's ElasticSearch by doing janusgraph.index.search.backend: elasticsearch.

AFAIK this hack doesn't work from OpenSearch v3. Do you think JanusGraph can "officially" support OS v3? Since ElasticSearch is not Apache 2.0 anymore, and OpenSearch currently is, I wanna move away from ES to OS. I'm more than happy help you, if anything is needed from my side.

Thank you.

[MattiJarvinen]

Just came to ask the same question. I'm trying to keep my stack as much as possible on the FOSS side. I've got burned so many times with corporate licensing hikes that I'd rather stay on the safe side.

Anyhow the Elastic Search code seems to be in https://github.com/JanusGraph/janusgraph/tree/master/janusgraph-es

From the looks of it there might be a lot that could be reused like the whole rest.util, es.compat, mapping... but even peeking into ElasticSearchIndex.java gives me the shivers 1512 lines of code.

Maybe all it would take would be (oh drak, why am I saying this like its an easy task):

• renaming from es to opensearch ( I hate abbreviations )
• check that it works with 2.x
• going through the OpenSearch changelog from 2 -> 3
• adjusting changes case by case
• check that it works with 3.x
• PR
• list all 3.x improvements in a feature improvement ticket

I wish we get lucky but given the state of JanusGraph development is almost at standstill I wouldn't hold my breath.

@porunov, as I've seen you've been active lately, has there been any plans for this and if anyone would start working with this how should they proceed?

[porunov]

I see there is a bit of confusion around ES licensing.
JanusGraph is using only permissive dependencies and doesn’t include any libraries with restrictive licenses.
What about ElasticSearch Java Client? - It’s Apache 2.0 - please, check here: https://github.com/elastic/elasticsearch-java

Meaning, we can safely use it as a dependency - that we do use.

Now, you may want to use janusgraph-es with ElasticSearch Server - and that’s the part where you will need to select ES license that is not Apache 2. You either use their Basic - Free ES distribution or Enterprise - Paid distribution. Both have some restrictions that I won’t go into details as I’m not a lawyer. However, for typical scenarios you should be able to run Basic Tier for your production use-cases just fine.

Regarding OpenSearch - absolutely, we should support it. However, it’s currently backward compatible with ES 7 I believe. Meaning, we can simply use our current janusgraph-es (fully Apache 2.0) with OpenSearch without any problems.
The only thing I heard is that people force-specify ES version “7” in JanusGraph properties to be able to work with OpenSearch. That’s because JanusGraph will use different features mode depending on ElasticSearch server runtime version that it fetched during the first connection, but OpenSearch had different versioning.

Of course, if there are some breaking changes we should adapt the code so that it’s compatible with both OpenSearch and ElasticSearch. As far as I remember some people used JanusGraph with OpenSearch 2 several years ago. I never used OpenSearch myself, so can’t comment on the compatibility, but I don’t think there will be too many breaking changes when using OpenSearch 3 (perhaps it just works already?).

Anyways, my vote is +1 for adding OpenSearch compatibility.
To do so, we would probably just need to extend our testing suite to include OpenSearch 2 and 3 (in addition to ES 6,7,8,9 tests). That probably will require several small configuration changes (to pin ES versions when running on top of OpenSearch) and add suites to our GitHub Actions.

If there are any volunteers - ping me in the PR and I will happily review it.