SOLR-17531: Use new unified GC log options

[malliaridis]

https://issues.apache.org/jira/browse/SOLR-17531

Description

This is a follow-up to #2792 for fixing issues and cleaning up GC_LOG_OPTS configurations.

Solution

Use the new unified GC logging configuration.

Tests

No tests were added due to it's complexity. If you have any recommendations for how to test GC configurations, please let me know.

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, not available for branches on forks living under an organisation)
• 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

[epugh]

LGTM. I love that it feels like a lot of "weight" has been taken out of these scripts. Having said that, I wonder if you should drop a note to [email protected] asking for another set of eyes? Since GC is a dark art! With no tests!

[gerlowskija]

Is this PR mostly about removing redundancy, or is it changing the effective defaults to be more in line with best-practices?

e.g. G1GC - are we moving away from it towards something else, or is it merely disappearing from our scripts because the JVM itself uses it as a default, etc.

[malliaridis]

I tried to keep the settings the same and remove redundancy / update to new notation. G1GC is the default GC since Java 9. With Java 21 we also have Generational ZGC which could be a nice feature to enable, but I am not familiar enough to tune the configuration. This is also why I was looking for GC experts to improve the existing configuration and make sure the config I "migrated" is free of bugs.

In JDK 17 support for some JDK 8 log-related configs has been dropped. See https://confluence.atlassian.com/confkb/unrecognized-jvm-gc-options-when-using-jdk-11-17-1002472841.html for details.

[risdenk]

I think I prefer the GC being explicit instead of relying on whatever JDK value is the default. The logging cleanup configs look good, but I would keep the G1GC configs.

[malliaridis]

I think I prefer the GC being explicit instead of relying on whatever JDK value is the default. The logging cleanup configs look good, but I would keep the G1GC configs.

I was thinking the same when I was editing it, thinking that if the defaults may change under certain circumstances, then we will not have a "reproducible" state. But for the same reason we would have to include all other defaults as well.

I tried to understand why this was added in the first place, and it seemed to be some pre JDK 9 stuff, where G1GC was not the default GC and had to be configured explicitly. Since we had a lot of legacy JDK configuration, I decided to remove it during the cleanup. Not sure if there were other reasons though, as I never had to configure the JDK before (besides memory).

[risdenk]

I think I prefer the GC being explicit instead of relying on whatever JDK value is the default. The logging cleanup configs look good, but I would keep the G1GC configs.

I was thinking the same when I was editing it, thinking that if the defaults may change under certain circumstances, then we will not have a "reproducible" state. But for the same reason we would have to include all other defaults as well.

I tried to understand why this was added in the first place, and it seemed to be some pre JDK 9 stuff, where G1GC was not the default GC and had to be configured explicitly. Since we had a lot of legacy JDK configuration, I decided to remove it during the cleanup. Not sure if there were other reasons though, as I never had to configure the JDK before (besides memory).

https://issues.apache.org/jira/browse/SOLR-13394 is where g1 was changed to be the default. I still think we should be explicit about using G1GC and make an explicit change away from it not just to what the JDK defaults to.

[dsmiley]

I agree with what Kevin said. Basically, explicitly enable G1GC because it's a rather important choice to not make an explicit decision on. But otherwise, no need to configure what doesn't need to be configured.

[malliaridis]

Since this PR is only addressing GC log options now, should we address other related issues here as well? We could resolve the following outdated PRs:

• SOLR-15281 / SOLR-15281: Add optional SOLR_GC_LOGS_DIR and SOLR_GC_LOG_FILE options for bin/solr #45
• SOLR-15104 / SOLR-15104: add SOLR_GC_LOG_PRESTART_ARCHIVE option to bin/solr #16
• SOLR-15104: add timestamp in default gc_log name lucene-solr#2289