Hi Andrew,
I'm having problems with replaying recovery logs, where the
replay appears to be deadlocking itself. I'm getting the following error:
2008-06-26 09:53:30,103 ERROR
org.continuent.sequoia.controller.recoverylog.RecoverThread - Recovery
process failed to replay transaction 1110: request
StatementExecuteUpdateTask from transaction 1110 (update... ) (Backend
AndyCluster - BackendWorkerThread for backend 'DB-BACKUP' with RAIDb
level:1 failed (A lock could not be obtained within the time requested.
As an example, consider the following simplified scenario:
I have a table 'test':
create table test ( a int , b int )
insert into test values ( 1, 1 )
we then have two transactions, t1 & t2 each in different threads which
do the following:
1) t1: update test set b = 2 where a = 1
2) t2: update test set b = 3 where a = 1
3) t1: commit
4) t2: commit
normally, this will work fine, when t2 executes, it is blocked on a
lock, but as soon as t1 commits, the lock is freed and t2 then commits.
however, if you replay the transaction log, all the statements are
executed sequentially, and what I think is happening is that the 2nd
statement hangs and eventually has a lock timeout, as t1 will not be
commited until after it.
This means that you can't recover, as you can't replay the log.
Is my understanding correct, and if so, is there anything I can do
about this?
There is something wrong here because the recovery log stores queries in
the execution order and not in their arrival order.
This means that the scenario you are describing should not be logged
this way in the recovery log.
Could you provide a dump of your recovery log content?
Which version of Sequoia are you using?
Are all your database backends running the same database engine?
Thanks for your feedback,
Emmanuel
--
Emmanuel Cecchet
FTO @ Frog Thinker
Open Source Development & Consulting
--
Web: http://www.frogthinker.org
email: [EMAIL PROTECTED]
Skype: emmanuel_cecchet
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