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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4741) Make Derby work reliably in the presence of thread interrupts
Date Wed, 08 Dec 2010 09:17:02 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12969252#action_12969252
] 

Kristian Waagan commented on DERBY-4741:
----------------------------------------

Thanks, Dag.

> I guess I have tended to treat them the same. I'll try to improve ;-)

Not sure there is something to improve here, I guess this is a question about personal preference.
Explicit initialization of instance variables used to result in two assignments (first the
default value for the type, and then the explicit value), which is kind of unnecessary if
both assignments use the same value. I don't know if this is still the case.

And I have become quite accustomed to use the "Step over" or "Run to cursor" in the debugger
:)
Finally, if the initial value isn't the default for the data type, then you have to assign
the correct value anyway - either in the constructor or as an instance variable initializer
(i.e. private int i = 3).


Thanks for working on the interrupt issue! I think it is of great value for Derby to be able
to handle interrupts better. This is especially important when/if other software products
used together with Derby use Thread.interrupt() internally.

> 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-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,
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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