[OAK-3172] Unreleased closed sessions can keep a root reference from getting collected

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.3.8, 1.4
• Component/s: segmentmk
• Labels: compaction gc
• Epic Link: SegmentMK revision GC
• Assignee: Alex Deparvu
• Reporter: Alex Deparvu
• Created: 03/Aug/15 10:19
• Updated: 16/Feb/21 09:52
• Resolved: 06/Oct/15 15:29

Description

It looks like even if a component logs out a session, but keeps a reference to it around this will still prevent GC from running, as the session will wrap a root reference pointing to the moment/revision when the session was last accessed.

Extract from jvisualvm:

this     - value: org.apache.jackrabbit.oak.plugins.segment.SegmentId #505
 <- [106]     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentId[], value: org.apache.jackrabbit.oak.plugins.segment.SegmentId #505
  <- refids     - class: org.apache.jackrabbit.oak.plugins.segment.Segment, value: org.apache.jackrabbit.oak.plugins.segment.SegmentId[] #67 (120 items)
   <- segment     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentId, value: org.apache.jackrabbit.oak.plugins.segment.Segment #81
    <- [124]     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentId[], value: org.apache.jackrabbit.oak.plugins.segment.SegmentId #496
     <- refids     - class: org.apache.jackrabbit.oak.plugins.segment.Segment, value: org.apache.jackrabbit.oak.plugins.segment.SegmentId[] #17 (204 items)
      <- segment     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentId, value: org.apache.jackrabbit.oak.plugins.segment.Segment #17
       <- segmentId     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState, value: org.apache.jackrabbit.oak.plugins.segment.SegmentId #551
        <- base     - class: org.apache.jackrabbit.oak.plugins.segment.SegmentNodeBuilder, value: org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState #5557
         <- builder     - class: org.apache.jackrabbit.oak.core.MutableRoot, value: org.apache.jackrabbit.oak.plugins.segment.SegmentNodeBuilder #5652
          <- root     - class: org.apache.jackrabbit.oak.jcr.repository.RepositoryImpl$1, value: org.apache.jackrabbit.oak.core.MutableRoot #151
           <- sd     - class: com.adobe.granite.repository.impl.CRX3SessionImpl, value: org.apache.jackrabbit.oak.jcr.repository.RepositoryImpl$1 #117