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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4741) Make Derby work reliably in the presence of thread interrupts
Date Tue, 04 Jan 2011 23:40:48 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12977533#action_12977533

Dag H. Wanvik commented on DERBY-4741:

Thanks for your thoughts on this, Knut.

Here is another issue: The NIO Channel#force call is used to implement sync when we flush
the Derby log, cf. this call: 

LogToFile#flush -> LogAccessFile#syncLogAccessFile -> StorageRandomAccessFile#sync ->

The "false" here allows the skipping of flushing metadata, which makes this faster (at least
on Solaris) than the non-NIO
implementation of StorageRandomAccessFile#sync, which uses getFD().sync().

Unfortunately, an interrupt will make the getChannel().force call throw ClosedChannelException,
and I can't see an easy way
to recover from this, except assuming the log is corrupt and shutting down the database instance,
so we can recover on reboot.

If we switch back to using "getFD().sync()", we would lose the performance optimization, but
be resilient to interrupts.

So, unless somebody can see a way to finesse this problem, should be offer a knob to allow
a user to trade this performance optimization for interrupt resilience?

Aside: we also use StorageRandomAccessFile#sync in many other places, but in those situations
I find I am able to recover by closing the RAF, reopening and writing over again, since the
data to be written is known, e.g. in LogToFile#initLogFile. 

> Make Derby work reliably in the presence of thread interrupts
> -------------------------------------------------------------
>                 Key: DERBY-4741
>                 URL: https://issues.apache.org/jira/browse/DERBY-4741
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions:,,,,,,,,,,
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>         Attachments: derby-4741-a-01-api-interruptstatus.diff, derby-4741-a-01-api-interruptstatus.stat,
derby-4741-a-02-api-interruptstatus.diff, derby-4741-a-02-api-interruptstatus.stat, derby-4741-a-03-api-interruptstatus.diff,
derby-4741-a-03-api-interruptstatus.stat, derby-4741-a-04-api-interruptstatus.diff, derby-4741-a-04-api-interruptstatus.stat,
derby-4741-all+lenient+resurrect.diff, derby-4741-all+lenient+resurrect.stat, derby-4741-b-01-nio.diff,
derby-4741-b-01-nio.stat, derby-4741-b-02-nio.diff, derby-4741-b-02-nio.stat, derby-4741-b-03-nio.diff,
derby-4741-b-03-nio.stat, derby-4741-b-04-nio.diff, derby-4741-b-04-nio.stat, derby-4741-c-01-nio.diff,
derby-4741-c-01-nio.stat, derby-4741-kristians-01.diff, derby-4741-nio-container+log+waits+locks+throws.diff,
derby-4741-nio-container+log+waits+locks+throws.stat, derby-4741-nio-container+log+waits+locks-2.diff,
derby-4741-nio-container+log+waits+locks-2.stat, derby-4741-nio-container+log+waits+locks.diff,
derby-4741-nio-container+log+waits+locks.stat, derby-4741-nio-container+log+waits.diff, derby-4741-nio-container+log+waits.stat,
derby-4741-nio-container+log.diff, derby-4741-nio-container+log.stat, derby-4741-nio-container-2.diff,
derby-4741-nio-container-2.log, derby-4741-nio-container-2.stat, derby-4741-nio-container-2b.diff,
derby-4741-nio-container-2b.stat, derby.log, derby.log, InterruptResilienceTest.java, MicroAPITest.java,
> When not executing on a small device VM, Derby has been using the Java NIO classes java.nio.clannel.*
for file io.
> If thread is interrupted while executing blocking IO operations in NIO, the ClosedByInterruptException
will get thrown. Unfortunately, Derby isn't current architected to retry and complete such
operations (before passing on the interrupt), so the Derby database can be left in an inconsistent
state and we therefore have to return a database level error. This means the applications
can no longer access the database without a shutdown and reboot including a recovery.
> It would be nice if Derby could somehow detect and finish IO operations underway when
thread interrupts happen before passing the exception on to the application. Derby embedded
is sometimes embedded in applications that use Thread.interrupt to stop threads.

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