SOLR-16687: Add a SolrClassLoader to SolrZkClient

[laminelam]

https://issues.apache.org/jira/browse/SOLR-16687

Description

A Solr class loader is needed in SolrZKClient to instantiate classes part of modules.

This is part of a bigger PR to add support of AWS Secret Manager to store Zookeeper credentials.

Tests

Local integration tests.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide

[gerlowskija]

This looks 👍 so far. Given a bit more time for other folks to review and some automated tests, I'd be happy to merge!

[HoustonPutman]

I think the classloader needs to be used in both createZkCredentialsToAddAutomatically and createZkACLProvider as well.

[laminelam]

This looks 👍 so far. Given a bit more time for other folks to review and some automated tests, I'd be happy to merge!

Hi @gerlowskija
Added a test case to test SCL based instantiation, will add more tests (SC vs DCL scenarios) as part of the main PR to add support of AWS Secret Manager.

I have also changed the behavior in case of an Exception is raised when instantiating ZkACLProvider or ZkCredentialsInjector, it should fail-fast rather then ignoring it and go with the default ZkACLProvider/ZkCredentialsInjector which sets znodes permissions to OPEN_ACL_UNSAFE.

[laminelam]

I think the classloader needs to be used in both createZkCredentialsToAddAutomatically and createZkACLProvider as well.

Hi @HoustonPutman

I think a solrClassLoader is not needed for ZkACLProvider and ZkCredentialsProvider except if we add in the future custom implementations part of another contrib/module, but it doesn't hurt to add it now. I have added it to both methods.

[gerlowskija]

This LGTM from a testing perspective; it's not ideal but I've wracked my brain trying to come up with a more comprehensive way to do this, without much luck.

It'd be good to give Houston another few days to chime in though, since he had other concerns to speak to.

[HoustonPutman]

My concerns have been addressed!