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Posted to derby-dev@db.apache.org by "Mike Matrigali (Commented) (JIRA)" <ji...@apache.org> on 2012/02/27 23:37:48 UTC
[jira] [Commented] (DERBY-5632) Logical deadlock happened when
freezing/unfreezing the database
[ https://issues.apache.org/jira/browse/DERBY-5632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13217649#comment-13217649 ]
Mike Matrigali commented on DERBY-5632:
---------------------------------------
Here is the documentation for using freeze/unfreeze to do a backup. The expectation is that the freeze and unfreeze comes
from the same connection (or at least that is likely what is tested in derby).
http://db.apache.org/derby/docs/dev/adminguide/cadminhubbkup75469.html
I don't remember but think it might be likely that future connection requests are stalled while a database is frozen, as part of work
necessary to keep a database in an ok state for a user backup routine to be called. Logically you just need to stop writing transactions
but the implementation may just of have stall all connections.
Obviously this does not work well for the 3 separate script steps you describe, but would be good to know if your use case works for
the intended use of freeze/unfreeze. And even if derby only supports same connection freeze
and unfreeze, we should understand what is expected if the connection executing the freeze fails or exits before doing unfreeze.
> Logical deadlock happened when freezing/unfreezing the database
> ---------------------------------------------------------------
>
> Key: DERBY-5632
> URL: https://issues.apache.org/jira/browse/DERBY-5632
> Project: Derby
> Issue Type: Bug
> Components: Network Server
> Affects Versions: 10.8.2.2
> Environment: Oracle M3000/Solaris 10
> Reporter: Brett Bergquist
> Attachments: stack.txt
>
>
> Tried to make a quick database backup by freezing the database, performing a ZFS snapshot, and then unfreezing the database. The database was frozen but then a connection to the database could not be established to unfreeze the database.
> Looking at the stack trace of the network server, , I see 3 threads that are trying to process a connection request. Each of these is waiting on:
> at org.apache.derby.impl.store.access.RAMAccessManager.conglomCacheFind(Unknown Source)
> - waiting to lock <0xfffffffd3a7fcc68> (a org.apache.derby.impl.services.cache.ConcurrentCache)
> That object is owned by:
> - locked <0xfffffffd3a7fcc68> (a org.apache.derby.impl.services.cache.ConcurrentCache)
> at org.apache.derby.impl.store.access.RAMTransaction.findExistingConglomerate(Unknown Source)
> at org.apache.derby.impl.store.access.RAMTransaction.openGroupFetchScan(Unknown Source)
> at org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.updateIndexStatsMinion(Unknown Source)
> at org.apache.derby.impl.services.daemon.IndexStatisticsDaemonImpl.runExplicitly(Unknown Source)
> at org.apache.derby.impl.sql.execute.AlterTableConstantAction.updateStatistics(Unknown Source)
> which itself is waiting for the object:
> at java.lang.Object.wait(Native Method)
> - waiting on <0xfffffffd3ac1d608> (a org.apache.derby.impl.store.raw.log.LogToFile)
> at java.lang.Object.wait(Object.java:485)
> at org.apache.derby.impl.store.raw.log.LogToFile.flush(Unknown Source)
> - locked <0xfffffffd3ac1d608> (a org.apache.derby.impl.store.raw.log.LogToFile)
> at org.apache.derby.impl.store.raw.log.LogToFile.flush(Unknown Source)
> at org.apache.derby.impl.store.raw.data.BaseDataFileFactory.flush(Unknown Source)
> So basically what I think is happening is that the database is frozen, the statistics are being updated on another thread which has the "org.apache.derby.impl.services.cache.ConcurrentCache" locked and then waits for the LogToFile lock and the connecting threads are waiting to lock "org.apache.derby.impl.services.cache.ConcurrentCache" to connect and these are where the database is going to be unfrozen. Not a deadlock as far as the JVM is concerned but it will never leave this state either.
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