[ISSUE #10572] Add dual TTL policy for tiered storage read-ahead cache

[Houlong66]

Which Issue(s) This PR Fixes

• Fixes [Enhancement] Add dual TTL policy for tiered storage read-ahead cache #10572

Brief Description

This PR adds a native dual-TTL policy for the tiered storage read-ahead cache.

The new default behavior keeps unread prefetched entries for 180000ms after creation, then switches entries to a shorter 10000ms TTL after they are read. This gives consumers more time to consume read-ahead batches while allowing already-read entries to be released sooner.

Main changes:

• Add readAheadCacheCreateExpireDuration and readAheadCacheAfterReadExpireDuration to MessageStoreConfig.
• Keep readAheadCacheExpireDuration as the legacy single-TTL fallback.
• Build the read-ahead cache with Caffeine Expiry for create/read/update-specific expiration.
• Add focused tests for default resolution, fallback behavior, create/read/update expiration semantics, and inverted TTL configuration.
• Update the tieredstore README configuration table.

How Did You Test This Change?

export JAVA_HOME=/Library/Java/JavaVirtualMachines/openjdk-11.jdk/Contents/Home
mvn -pl tieredstore test -Dtest=MessageStoreFetcherImplCacheTest
mvn -pl tieredstore test -DfailIfNoTests=false

[codecov-commenter]

Codecov Report

❌ Patch coverage is 83.67347% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.16%. Comparing base (41a3a35) to head (2eaa01e).
⚠️ Report is 60 commits behind head on develop.

Files with missing lines	Patch %	Lines
...etmq/tieredstore/core/MessageStoreFetcherImpl.java	79.48%	5 Missing and 3 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10573      +/-   ##
=============================================
- Coverage      49.01%   48.16%   -0.85%     
+ Complexity     13485    13418      -67     
=============================================
  Files           1376     1378       +2     
  Lines         100527   100864     +337     
  Branches       12983    13047      +64     
=============================================
- Hits           49274    48584     -690     
- Misses         45251    46317    +1066     
+ Partials        6002     5963      -39     

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[RockteMQ-AI]

Review by github-manager-bot

Summary

Introduces a dual-TTL policy for the tiered storage read-ahead cache: unread entries use a longer createTtl (default 180s), then after first read switch to a shorter afterReadTtl (default 10s). Falls back to legacy single-TTL expireAfterAccess when both dual TTLs are disabled.

Findings

• [Info] MessageStoreFetcherImpl.java — The DualTtlExpiry implementing Caffeine's Expiry interface is clean and correct. expireAfterCreate/expireAfterUpdate return createNanos, expireAfterRead returns afterReadNanos — this gives the intended "long before read, short after read" semantics.
• [Info] resolveReadAheadCacheTtl() has solid fallback logic: both disabled → legacy; one disabled → use readAheadCacheExpireDuration as fallback for the missing one; both partially invalid → legacy. Well-covered by tests.
• [Info] TieredMessageStore.createFetcher() is extracted as a protected method to allow subclass override. The Javadoc correctly warns about virtual dispatch from constructor — good defensive documentation.
• [Info] memoryMaxSize changed from private to protected — necessary for the subclass override pattern. Acceptable.
• [Warning] DualTtlExpiry.expireAfterUpdate resets to createNanos on update. This means if a cache entry is re-put (same key), it gets the full create TTL again. The test dualTtlCache_readThenRePutResetsToCreateTtl confirms this is intentional. Just flagging this as a behavioral note: repeated writes to the same offset will keep entries alive at the longer TTL.
• [Info] The warning log when afterReadTtl >= createTtl is a nice touch — helps operators catch misconfiguration.
• [Info] Test coverage is comprehensive: default config, disabled dual TTL, partial fallback, invalid partial fallback, create-TTL expiry, after-read-TTL expiry, re-put reset, and the isAfterReadNotShorter edge case. The FakeTicker approach is clean.

Suggestions

• The README table still shows the old readAheadCacheExpireDuration description as "Read-ahead cache expiration time". Consider updating it to clarify it's now the legacy fallback, alongside the two new columns.

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Automated review by github-manager-bot