[fix][ml] Fix ledger trimming race causing cursor to point to deleted ledgers #24855
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… ledgers Problem: - getNumberOfEntriesInBacklog(isPrecise=false) could return negative values - Cursors could point to deleted ledgers after trim operations - Root cause: persistence ordering race between cursor advancement and ledger trimming Root Cause: When messages are acknowledged: 1. Cursor position advances in memory immediately 2. Cursor state persists to BookKeeper asynchronously 3. If ledger trimming occurs during the persistence delay, it uses the in-memory position 4. Ledgers get deleted before the cursor state is durably saved 5. On topic reload, cursor reverts to old persistent position pointing to deleted ledgers The Fix: Changed maybeUpdateCursorBeforeTrimmingConsumedLedger() to use the persistent cursor position (getPersistentMarkDeletedPosition) instead of the in-memory position (getMarkDeletedPosition) when determining which ledgers can be safely trimmed. This ensures ledgers are only deleted after the cursor advancement has been durably persisted to BookKeeper, preventing the cursor from pointing to deleted ledgers. Test Coverage: Added testCursorPointsToDeletedLedgerAfterTrim() which: - Simulates BookKeeper persistence delay (30 seconds) - Acknowledges messages asynchronously during the delay - Triggers ledger trimming - Verifies ledgers are NOT trimmed when persistent position hasn't advanced 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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@codelipenghui Please add the following content to your PR description and select a checkbox: |
poorbarcode
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Oct 15, 2025
Codecov Report❌ Patch coverage is
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## master #24855 +/- ##
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+ Coverage 38.36% 74.30% +35.93%
- Complexity 13123 33451 +20328
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+ Misses 81843 29521 -52322
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lhotari
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Oct 15, 2025
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LGTM, good work @codelipenghui
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@codelipenghui Does this problem apply to 3.0.x and 3.3.x? |
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@lhotari Yes, I think so. |
Technoboy-
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Oct 23, 2025
… ledgers (#24855) Co-authored-by: Claude <noreply@anthropic.com>
ganesh-ctds
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Oct 23, 2025
… ledgers (apache#24855) Co-authored-by: Claude <noreply@anthropic.com> (cherry picked from commit d56758f)
srinath-ctds
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… ledgers (apache#24855) Co-authored-by: Claude <noreply@anthropic.com> (cherry picked from commit d56758f)
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Summary
Fixes a critical race condition where ledger trimming could delete ledgers while cursors still pointed to them, causing:
getNumberOfEntriesInBacklogHere is an example topic internal-stats to show the issue
{ "entriesAddedCounter" : 947356, "numberOfEntries" : 14437764, "totalSize" : 7582862344, "currentLedgerEntries" : 402806, "currentLedgerSize" : 221336947, "lastLedgerCreatedTimestamp" : "2025-10-14T16:05:55.171Z", "waitingCursorsCount" : 0, "pendingAddEntriesCount" : 3, "lastConfirmedEntry" : "339371:402802", "state" : "LedgerOpened", "ledgers" : [ { "ledgerId" : 333163, "entries" : 76809, "size" : 173537945, "offloaded" : false, "underReplicated" : false }, ... { "ledgerId" : 339362, "entries" : 98219, "size" : 47366060, "offloaded" : false, "underReplicated" : false }, { "ledgerId" : 339365, "entries" : 544553, "size" : 288444337, "offloaded" : false, "underReplicated" : false }, { "ledgerId" : 339371, "entries" : 0, "size" : 0, "offloaded" : false, "underReplicated" : false } ], "cursors" : { "subscription" : { "markDeletePosition" : "333160:740812", "readPosition" : "339371:402809", "waitingReadOp" : true, "pendingReadOps" : 0, "messagesConsumedCounter" : 947397, "cursorLedger" : 339366, "cursorLedgerLastEntry" : 1044, "individuallyDeletedMessages" : "[(333160:742256..333160:742354],(333163:-1..333163:76808],(335756:-1..335756:153],(335761:-1..335761:16],(335765:-1..335765:193],(335770:-1..335770:16],(335773:-1..335773:13],(335776:-1..335776:32],(335779:-1..335779:98],(335783:-1..335783:19],(335787:-1..335787:120],(335792:-1..335792:350],(335795:-1..335795:40],(335797:-1..335797:71],(335799:-1..335799:161],(335801:-1..335801:32],(335803:-1..335803:100],(335805:-1..335805:293],(335807:-1..335807:30],(335809:-1..335809:58],(335811:-1..335811:1126],(335813:-1..335813:250],(335815:-1..335815:175],(335817:-1..335817:153],(335819:-1..335819:4853],(335821:-1..335821:291],(335823:-1..335823:121],(335825:-1..335825:369],(335827:-1..335827:8149],(335829:-1..335829:208],(335833:-1..335833:5],(335835:-1..335835:16138],(336566:-1..336566:0],(339193:-1..339193:281215],(339197:-1..339197:528770],(339201:-1..339201:567213],(339205:-1..339205:526913],(339209:-1..339209:221685],(339213:-1..339213:513837],(339217:-1..339217:218062],(339221:-1..339221:528247],(339225:-1..339225:281650],(339229:-1..339229:407551],(339233:-1..339233:414568],(339238:-1..339238:412851],(339242:-1..339242:72557],(339249:-1..339249:530444],(339257:-1..339257:523422],(339261:-1..339261:523159],(339265:-1..339265:552096],(339279:-1..339279:61660],(339283:-1..339283:529604],(339289:-1..339289:556833],(339293:-1..339293:541437],(339297:-1..339297:534261],(339306:-1..339306:294508],(339307:-1..339307:188358],(339314:-1..339314:81424],(339319:-1..339319:198963],(339323:-1..339323:521405],(339327:-1..339327:521142],(339342:-1..339342:379129],(339346:-1..339346:531631],(339350:-1..339350:519627],(339354:-1..339354:464938],(339358:-1..339358:252548],(339362:-1..339362:98218],(339365:-1..339365:544552],(339371:-1..339371:402720]]", "lastLedgerSwitchTimestamp" : "2025-10-14T15:55:55.155Z", "state" : "Open", "active" : true, "numberOfEntriesSinceFirstNotAckedMessage" : 14437771, "totalNonContiguousDeletedMessagesRange" : 69, "subscriptionHavePendingRead" : true, "subscriptionHavePendingReplayRead" : false, "properties" : { } } }, "schemaLedgers" : [ ], "compactedLedger" : { "ledgerId" : -1, "entries" : -1, "size" : -1, "offloaded" : false, "underReplicated" : false } }Root Cause
The issue occurs when:
The Fix
Changed
maybeUpdateCursorBeforeTrimmingConsumedLedger()inManagedLedgerImpl.java:2704-2705to use the persistent cursor position instead of the in-memory position to keep it consistent with the mark delete entry update in CursorContainer from cursor.delete().This ensures ledgers are only deleted after cursor advancement has been durably persisted to BookKeeper.
Test Coverage
Added
testCursorPointsToDeletedLedgerAfterTrim()inManagedLedgerTest.javawhich:Verification
Without the fix, the test fails because:
With the fix, the test passes because:
Documentation
docdoc-requireddoc-not-neededdoc-complete