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https://issues.apache.org/jira/browse/OAK-12119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18062057#comment-18062057
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Rishabh Daim commented on OAK-12119:
------------------------------------
The proposed fix is as follows:
*Fix*
Store the CompactionResult in the *GarbageCollector* after
_*compactFull()/compactTail()*_ and thread it into the subsequent _*cleanup()*_
call.
This requires adding the 2-arg _cleanup(Context, CompactionResult)_ overload to
the *GarbageCollectionStrategy* interface (the implementation already exists on
{*}AbstractGarbageCollectionStrategy{*}).
cc [~reschke]
> Offline Compaction does not persist compacted head into gc.log
> --------------------------------------------------------------
>
> Key: OAK-12119
> URL: https://issues.apache.org/jira/browse/OAK-12119
> Project: Jackrabbit Oak
> Issue Type: Bug
> Reporter: Rishabh Daim
> Assignee: Rishabh Daim
> Priority: Critical
>
> *Root Cause*
> The offline compaction in *Compact.run()* calls *compactFull()* and
> *cleanup()* as two separate calls, but the _CompactionResult_ from compaction
> is silently discarded between them.
>
> *Call chain:*
> Compact.run()
> ├─ store.compactFull()
> │ └─ garbageCollector.compactFull(strategy).isSuccess()
> │ ^^^^^^^^^^^
> │ CompactionResult.succeeded(...) is returned but thrown away!
> │
> └─ store.cleanup()
> └─ garbageCollector.cleanup(strategy)
> └─ strategy.cleanup(context) ← no-arg overload
> └─ AbstractGarbageCollectionStrategy.cleanup(Context):
> return cleanup(context, CompactionResult.skipped(...))
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Always creates a SKIPPED
> result!
>
> Why *gc.log* is never written:
> In *AbstractGarbageCollectionStrategy.java:88–95:*
> // Standalone cleanup always creates a SKIPPED result
>
> {code:java}
> public List<String> cleanup(Context context) throws IOException {
> return cleanup(context, CompactionResult.skipped(...));
> }{code}
> *CompactionResult.skipped(...)* inherits *requiresGCJournalEntry()* from
> the base class, which returns false (line 216).
> Then in *newCleanupStrategyContext()* at line 295–297:
>
> {code:java}
> public GCJournal getGCJournal()
> { return compactionResult.requiresGCJournalEntry() ?
> context.getGCJournal() : null; // ↑ false for skipped → returns null!
> }{code}
> *DefaultCleanupStrategy* receives null for gcJournal, so it skips the
> gcJournal.persist(...) call entirely.
> Contrast with online (integrated) GC:
> The *AbstractGarbageCollectionStrategy.run()* method calls *cleanup(context,
> compactionResult)* with the actual *CompactionResult.succeeded(...)* — that's
> why gc.log works online
> but not offline.
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