[poorbarcode]

Motivation

A cached entry can retain a small slice of a much larger inbound direct-memory buffer. The existing managedLedgerCacheCopyEntries setting avoids that retention by copying entry payloads, but changing it currently requires restarting the broker and recreating caches. Operators need to enable or disable copying for future cache inserts without restarting the broker or clearing useful cached data.

This change is extracted from #27110 and can be reviewed and merged independently of request-frame memory tracking and limiting.

Modifications

This change makes the existing managedLedgerCacheCopyEntries setting dynamically configurable. Existing and newly created entry caches read one shared policy when inserting entries, so updates do not require cache recreation. Updates affect future inserts without clearing or recopying existing entries, while BookKeeper batch reads continue to force copying.

• Mark the broker setting as dynamic and propagate configuration updates to the managed-ledger factory through the existing configuration listener mechanism.
• Store the copy policy in one volatile factory configuration field and remove per-cache snapshots that can miss or overwrite concurrent updates during cache creation.
• Preserve coverage for cache creation and publication races, overlapping updates, batch inserts, asynchronous storage reads, and existing-entry retention.
• Add an independent broker test for enabling, disabling, and deleting the dynamic override, and document the behavior in broker, standalone, and deployment configuration files.

Validation: full ./gradlew quickCheck and 41 focused managed-ledger and broker tests passed with retries disabled.

Does this pull request potentially affect one of the following parts:

• Broker configuration: managedLedgerCacheCopyEntries becomes dynamic; its default remains false.
• Public API
• Wire protocol
• Metrics
• Dependencies

Best practice

Enable managedLedgerCacheCopyEntries when cached entry slices retain substantially larger inbound buffers, using pulsar-admin brokers update-dynamic-config --config managedLedgerCacheCopyEntries --value true. This trades payload-copy work for reduced retention of larger source buffers. Existing cached entries keep their original buffers until normal eviction or removal, so enabling copying does not immediately reclaim their memory. Set the value to false to stop copying future normal inserts, or delete the dynamic override to restore the broker's startup setting; batch reads still copy entries.

[lhotari]

LGTM