Clarify whether the supported Solr versions includes Solr 10

[plumdog]

Solr 10 has been released. https://solr.apache.org/downloads.html#solr-1000

https://github.com/apache/solr-operator/blob/main/docs/upgrade-notes.md#solr-versions just shows "9.4+" and it isn't clear to me whether this just means ">=9.4, <10" or ">=9.4".

[janhoy]

Feel free to test whether 10.0 works already. It may work partially, but obviously not support any new features. So perhaps some disclaimer about what works and not would be good to add. I have no idea as I have not tested it yet.

[HoustonPutman]

Yeah, I tried testing before the release but got caught and didn't have time to deep dive. We should probably put <10 until we can figure it out...

[HoustonPutman]

Ok, I've gotten the E2E tests to work on my laptop again, and it's not looking good for Solr 10 or 9.10 even...

I'll do some more work to isolate working versions and update our docs. Then we can start to fix things.

[HoustonPutman]

Ok from my findings:

• Solr 9.8 - 0 failures
• Solr 9.9 - 2 flaky tests: (both failed 2 out of 3 runs)
  • Scale Up with replica migration using an ingress for node addresses
  • Scale Down without replica migration
• Solr 9.10 - 0 failures
• Solr 10.0 - No tests pass

So I think we are good for the 9.x line at least for the things that are tested. Solr 10 does not work at all, and we need to fix the operator and/or solr. In the meantime, I'll make a PR for the docs.

[epugh]

Let me know if some of the CLI changes made life hard... I'm having a small bit of regret on some changes, like eliminating the -c option in Solr 10 versus just making it a no-op when I run bin/solr start -c.....

[janhoy]

Yea, making -c a no-op would be smoother. But too late for 10.0.0.

[HoustonPutman]

We could just support 10.1.0, and have that fixed there. I'm not sure how we would support 9.x and 10.x at the same time if we can't pass -c to both.