Main Issue: #26815

Motivation

A read-only managed ledger has no current write handle. Its close path therefore skips the write-handle callback that normally releases cached read handles, leaving their metadata listeners registered. A read submitted after close can also open another handle and repopulate the cache.

Modifications

• Invalidate cached handles on normal and fenced close, including opens whose futures have not completed yet.
• Mark the read-only ledger as closing before draining the cache. Reject subsequent opens and recheck after cache insertion so a concurrent close cannot leave a late insertion behind.
• Reuse existing asynchronous invalidation cleanup. One close failure does not skip other cached handles, and repeated close does not close the same cached handle again.

Writable managed-ledger behavior is unchanged. Temporary initialization-handle cleanup is covered independently by #26817. This change initiates cached-handle cleanup; it does not make the managed-ledger close callback wait for every pending BookKeeper open/close.

Verifying this change

• Make sure that the change passes the CI checks.

Local validation passed as described below. Full CI validation is still pending.

ReadOnlyManagedLedgerHandleCloseTest covers six cases: normal/fenced cleanup, a pending open completing after close, rejection of reads after normal/fenced close, and cleanup of multiple cached handles when one close fails. It also verifies an empty cache, exactly-once cleanup on repeated close, and no new BookKeeper open after close. Assertions run before fixture cleanup.

With the tests unchanged and only the production changes removed (base 1046481c970067cbca9c80a25a98257b9179a3da), all six cases fail: handles are not closed, the pending-open cache entry remains, or reads still succeed after close.

With the fix restored, all six cases and ten existing read-only tests pass (16 total), along with quickCheck:

./gradlew :managed-ledger:test \
  --tests '*ReadOnlyManagedLedgerHandleCloseTest' --tests '*ReadOnlyCursorTest' \
  --tests '*ReadOnlyManagedLedgerImplTest' \
  -PtestRetryCount=0 -PtestFailFast=false -PtestMaxParallelForks=1 --max-workers=2 quickCheck

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

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment