SOLR-16906: Correctly capture REPLICATION metrics in Prometheus config

[osyoyu]

https://issues.apache.org/jira/browse/SOLR-16906

Description

The Prometheus exporter config provided with Solr seems to unintentionally ignore replication-related metrics. This change lets the Prometheus exporter correctly collect/expose them.

Solution

Fix the regex that intends to match REPLICATION category metrics. REPLICATION metrics start with REPLICATION./replication, but the previous regex misses the / (slash) and fails to match them.

Tests

Start a solr-exporter process and make a request to http://localhost:9983/metrics and confirm metrics such as solr_metrics_core_replication_leader or solr_metrics_core_requests_total{category="REPLICATION"} show up.

$ cd solr/packaging/build/dev
$ ./bin/solr start -f
$ ./bin/solr create -c films -s 2 -rf 2

# in an another shell
$ ./prometheus-exporter/bin/solr-exporter -f ../../../prometheus-exporter/build/packaging/conf/solr-exporter-config.xml --baseurl http://localhost:8983/solr

# another shell
$ curl -s http://localhost:8989 | grep REPLICATION
solr_metrics_core_replication_leader{category="REPLICATION",handler="/replication",core="films",base_url="http://localhost:8983/solr",cluster_id="a8ed8a12b2",} 1.0
solr_metrics_core_requests_total{category="REPLICATION",handler="/replication",internal="false",core="films",base_url="http://localhost:8983/solr",cluster_id="a8ed8a12b2",} 0.0
...

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

[HoustonPutman]

Thank you for finding this! Would you mind creating a JIRA at https://issues.apache.org/jira/projects/SOLR/summary so that we can track this for the next release?

Otherwise I'll test locally and commit once the JIRA has been created 🙂

[osyoyu]

Sure 👍

[osyoyu]

JIRA Issue created and commit message updated (force pushed). Let me know if I need to do something else!
https://issues.apache.org/jira/browse/SOLR-16906

[HoustonPutman]

Let me know if you are ok with that name in the changelog entry.

[osyoyu]

No problems with me. Thanks!