OpenSearch support on the long run

[spapadop]

Firstly, a big thanks to the maintainers of this repo and JustWatch as I'm reading that they did all the heavy lifting for this exporter few years back.

I have a question regarding your stand on supporting OpenSearch. I know that currently APIs are fairly the same and unless a breaking change comes from Elasticsearch or OpenSearch side the exporter should continue to work fine with newer versions of both. I also tested it against OpenSearch v2.15 and things work as expected. Naturally --es.slm fails as this is an Elasticsearch feature, but that's basically it.

So, is it more like as long as OpenSearch doesn't break compatibility it's happily supported but if they go down that path you have no interest in supporting it? Or there is a commitment to keep supporting both?

And one last question, would you be open to contributions like adding new metrics for OpenSearch ISM statistics (--os.ism) targeting the index lifecycle management plugin on the OpenSearch world?

Thanks a lot in advance for your input.

[spapadop]

pinging the maintainers @sysadmind @SuperQ, if you could please have a look on this.

[sysadmind]

I would like to try to support both as much as possible. It seems that for the foreseeable future, they're similar enough where I think it makes sense to keep them under the same exporter. I'm happy to accept PRs that add collectors that are opensearch specific. I think it would also be a good idea for us to add tests for opensearch as we go along where possible. I'll add something to the README about opensearch.