SOLR-18165 Complete dot-separated metric name migration

[janhoy]

https://issues.apache.org/jira/browse/SOLR-18165

PR #4223 converted the majority of Solr metric instrument names from underscore_delimited
to dot.separated OTel standard naming. Several files were missed or only partially converted.
This PR completes that work.

Files changed

AuditLoggerPlugin.java — all 7 metric names were still in old solr_auditlogger_* format;
converted to solr.auditlogger.*.

CaffeineCache.java — the default base metric name "solr_caffeine_cache" and the five
metric name suffixes (_lookups, _ops, _size, _ram_used, _warmup_time) were still using
underscores as namespace separators. Converted to "solr.caffeine_cache" base with
dot-prefixed suffixes (.lookups, .ops, .size, .ram_used, .warmup_time).

ZkContainer.java — all 7 metrics still in old solr_zk_* format; converted to solr.zk.*.

OtelMetrics.java (cross-dc-manager) — all 8 metric names were in old crossdc_consumer_*
format. The NAME_PREFIX constant is updated to "crossdc.consumer." and all suffix strings
are converted to dot-separated.

Metric name mapping

Old name	New name	Comments
solr_auditlogger_count	solr.auditlogger.count
solr_auditlogger_errors	solr.auditlogger.errors
solr_auditlogger_lost	solr.auditlogger.lost
solr_auditlogger_request_times	solr.auditlogger.request_times	Leaf kept as compound word
solr_auditlogger_queue	solr.auditlogger.queue
solr_auditlogger_queued_time	solr.auditlogger.queued_time	Leaf kept as compound word
solr_auditlogger_async_enabled	solr.auditlogger.async_enabled	Leaf kept as compound word
solr_caffeine_cache_lookups	solr.caffeine_cache.lookups	caffeine_cache is the cache type name
solr_caffeine_cache_ops	solr.caffeine_cache.ops
solr_caffeine_cache_size	solr.caffeine_cache.size
solr_caffeine_cache_ram_used	solr.caffeine_cache.ram_used	Leaf kept as compound word
solr_caffeine_cache_warmup_time	solr.caffeine_cache.warmup_time	Leaf kept as compound word
solr_zk_ops	solr.zk.ops
solr_zk_read	solr.zk.read
solr_zk_watches_fired	solr.zk.watches_fired	Leaf kept as compound word
solr_zk_written	solr.zk.written
solr_zk_cumulative_multi_ops_total	solr.zk.cumulative.multi_ops.total	Leaf kept as compound word;
solr_zk_child_fetches	solr.zk.child.fetches
solr_zk_cumulative_children_fetched	solr.zk.cumulative.children_fetched	Leaf kept as compound word
crossdc_consumer_input_msg_total	crossdc.consumer.input.msg.total	Consider _total?
crossdc_consumer_input_req_total	crossdc.consumer.input.req.total
crossdc_consumer_collapsed_total	crossdc.consumer.collapsed.total
crossdc_consumer_output_total	crossdc.consumer.output.total
crossdc_consumer_output_batch_size	crossdc.consumer.output.batch_size	Leaf kept as compound word
crossdc_consumer_output_backoff_time	crossdc.consumer.output.backoff_time	Leaf kept as compound word
crossdc_consumer_output_time	crossdc.consumer.output.time
crossdc_consumer_output_first_attempt_time	crossdc.consumer.output.first_attempt_time	Leaf kept as compound word

Questions:

• Do you agree with the name mappings above?
• The two existing solr_zk_child_fetches and solr_zk_cumulative_children_fetched both talk about the same thing, only cumulative is total? So a bit strange that they use child_fetches vs children_fetched. Should solr.zk.child.fetches instead be solr.zk.child_fetches to align with solr_zk_cumulative_children_fetched? Or should we do a breaking change here and align naming?
• The crossdc consumer metrics do not have a solr. prefix. The corresponsing producer metrics use solr.core.crossdc.producer.XXX. So ideally consumer would also use solr.core.crossdc.consumer.XXX. Or why the core part in there? Should we do a breaking change here, for one or for both?

[Copilot]

Pull request overview

Completes the remaining OpenTelemetry metric instrument renames from underscore-delimited names to dot-separated names as part of SOLR-18165.

Changes:

• Migrates AuditLoggerPlugin metric names to solr.auditlogger.*.
• Migrates CaffeineCache metric base name and suffixes to solr.caffeine_cache.*.
• Migrates ZooKeeper metrics in ZkContainer to solr.zk.*, and cross-dc consumer metrics to crossdc.consumer.*.
• Adds an unreleased changelog entry for this follow-up migration.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
solr/cross-dc-manager/src/java/org/apache/solr/crossdc/manager/consumer/OtelMetrics.java	Renames cross-dc consumer OTel instrument names to dot-separated format.
solr/core/src/java/org/apache/solr/security/AuditLoggerPlugin.java	Renames audit logger OTel instrument names to solr.auditlogger.*.
solr/core/src/java/org/apache/solr/search/CaffeineCache.java	Renames caffeine cache OTel instrument base name and suffixes to dot-separated format.
solr/core/src/java/org/apache/solr/core/ZkContainer.java	Renames ZooKeeper OTel instrument names to solr.zk.*.
changelog/unreleased/SOLR-18165-More-dot-separated-metric-names.yml	Adds changelog entry documenting the additional metric renames.

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[Copilot]

The metric name solr.zk.child.fetches introduces an extra hierarchy level (child → fetches) even though the pre-migration name treated this as a single compound concept (child_fetches). In this same block, other compound leaves keep underscores (e.g. watches_fired, children_fetched, multi_ops), so this one stands out and makes the naming inconsistent. Consider using solr.zk.child_fetches instead to keep the compound token intact (and keep the mapping closer to the previous name).

[janhoy]

This is what I also commented in the Questions section above. So probably use child_fetches.

[janhoy]

@chan-dx I ping you here since I could not add you as reviewer...