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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 Mon, 11 Oct 2010 12:48:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12919805#action_12919805
] 

Dag H. Wanvik commented on DERBY-4741:
--------------------------------------

Thanks, Knut! I agree it's a bit weird that the JRE is a little schizophrenic about the interrupt
flag. I think we should try to be consistent when we throw, no matter where/after which Java
API call Derby detects it. If we do retain the interrupt flag, I think it adds to the argument
for making the exception session-level, since the user would need to undertake some cleaning
up anyway, or else the next Derby call would fail as well. Probably this would be the use
case for connection pools. As to arguments for making the error statement level, I guess if
one just wants to stop a run-away query, one would possibly prefer that just the statement
failed.  A thing to consider here is the new JDBC 4.1 method Connection#abort:
This would be the future portable way of stopping a run-away transaction. It will also close
the the connection.

This patch passed regressions, for what it's worth.

> 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: 10.2.1.6, 10.2.2.0, 10.3.1.4, 10.3.2.1, 10.3.3.0, 10.4.1.3, 10.4.2.0,
10.5.1.1, 10.5.2.0, 10.5.3.0, 10.6.1.0
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>         Attachments: 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,
xsbt0.log.gz
>
>
> 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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