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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4055) Space may not be reclaimed if locks are not available after three retries (code inspection)
Date Thu, 12 Feb 2009 20:30:59 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4055?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kathey Marsden updated DERBY-4055:
----------------------------------

    Priority: Major  (was: Minor)

With revision 743867, checked in reproduction for the case where it cannot get the row lock
after three tries.
enable store.ClobReclamationTest.xtestMultiThreadUpdateSingleRow()
If multiple threads are trying to update the same row, reclamation doesn't happen and with
derby.debug.true=Daemon trace see in the log many instances of:
DEBUG DaemonTrace OUTPUT:   gave up after 3 tries to get row lock Reclaim COLUMN_CHAIN...





> Space may not be reclaimed if locks are not available after three retries (code inspection)
> -------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4055
>                 URL: https://issues.apache.org/jira/browse/DERBY-4055
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.0.0
>            Reporter: Kathey Marsden
>
> I don't have a reproduction for these cases but there are two places in ReclaimSpaceHelper
where reclamation will give up after three tries if it cannot obtain the lock to reclaim the
space.  The first code path is:
> ContainerHandle containerHdl = 
> 			openContainerNW(tran, container_rlock, work.getContainerId());
> 		if (containerHdl == null)
> 		{
> 			tran.abort();
> 			if (SanityManager.DEBUG)
>             {
>                 if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                 {
>                     SanityManager.DEBUG(
>                         DaemonService.DaemonTrace, " aborted " + work + 
>                         " because container is locked or dropped");
>                 }
>             }
> 			if (work.incrAttempts() < 3) // retry this for serveral times
>             {
> 				return Serviceable.REQUEUE;
>             }
> 			else
>             {
>                 // If code gets here, the space will be lost forever, and
>                 // can only be reclaimed by a full offline compress of the
>                 // table/index.
>                 if (SanityManager.DEBUG)
>                 {
>                     if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                     {
>                         SanityManager.DEBUG(
>                             DaemonService.DaemonTrace, 
>                             "  gave up after 3 tries to get container lock " + 
>                             work);
>                     }
>                 }
> 				return Serviceable.DONE;
>             }
> 		}	
> the second is:
> 	RecordHandle headRecord = work.getHeadRowHandle();
> 		if (!container_rlock.lockRecordForWrite(
>                 tran, headRecord, false /* not insert */, false /* nowait */))
> 		{
> 			// cannot get the row lock, retry
> 			tran.abort();
> 			if (work.incrAttempts() < 3)
>             {
> 				return Serviceable.REQUEUE;
>             }
> 			else
>             {
>                 // If code gets here, the space will be lost forever, and
>                 // can only be reclaimed by a full offline compress of the
>                 // table/index.
>                 if (SanityManager.DEBUG)
>                 {
>                     if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                     {
>                         SanityManager.DEBUG(
>                             DaemonService.DaemonTrace, 
>                             "  gave up after 3 tries to get row lock " + 
>                             work);
>                     }
>                 }
> 				return Serviceable.DONE;
>             }
> 		}
> If working to get a reproduction for these cases, you can set derby.debug.true=DaemonTrace
and look for "gave up" in the derby.log.

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