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https://issues.apache.org/jira/browse/LUCENE-6989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15737650#comment-15737650
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Uwe Schindler commented on LUCENE-6989:
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The current reply by Alan Bateman was:
{quote}
sun.misc.Cleaner was indeed on the original list of APIs for JEP 260 to
identify as a "critical internal API". It turned out not to be useful
because it would have required some way to get the Cleaner in the first
place. That lead to the "new" hack that is reading the private "cleaner"
field from DBB and treating it as a Runnable. That hack now breaks
because setAccessible has changed in jdk-9+148 to align with the JSR 376
proposal tracked as #AwkwardStrongEncapsulation.
No need to panic though, there is an update to JEP 260 coming soon for
this specific need. Details TDB but it will probably be a method in
jdk.unsupported module. It does mean that libraries using the old (or
"new") hacks will need to change. I hope it will be seen as a reasonable
compromise for this generally awkward issue.
{quote}
I am free to change the hack again... :-)
> Implement MMapDirectory unmapping for coming Java 9 changes
> -----------------------------------------------------------
>
> Key: LUCENE-6989
> URL: https://issues.apache.org/jira/browse/LUCENE-6989
> Project: Lucene - Core
> Issue Type: Task
> Components: core/store
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Labels: Java9
> Fix For: 6.0
>
> Attachments: LUCENE-6989-disable5x.patch,
> LUCENE-6989-disable5x.patch, LUCENE-6989-fixbuild148.patch,
> LUCENE-6989-v2.patch, LUCENE-6989.patch, LUCENE-6989.patch,
> LUCENE-6989.patch, LUCENE-6989.patch
>
>
> Originally, the sun.misc.Cleaner interface was declared as "critical API" in
> [JEP 260|http://openjdk.java.net/jeps/260 ]
> Unfortunately the decission was changed in favor of a oficially supported
> {{java.lang.ref.Cleaner}} API. A side effect of this change is to move all
> existing {{sun.misc.Cleaner}} APIs into a non-exported package. This causes
> our forceful unmapping to no longer work, because we can get the cleaner
> instance via reflection, but trying to invoke it will throw one of the new
> Jigsaw RuntimeException because it is completely inaccessible. This will make
> our forceful unmapping fail. There are also no changes in Garbage collector,
> the problem still exists.
> For more information see this [mailing list
> thread|http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-January/thread.html#38243].
> This commit will likely be done, making our unmapping efforts no longer
> working. Alan Bateman is aware of this issue and will open a new issue at
> OpenJDK to allow forceful unmapping without using the now private
> sun.misc.Cleaner. The idea is to let the internal class sun.misc.Cleaner
> implement the Runable interface, so we can simply cast to runable and call
> the run() method to unmap. The code would then work. This will lead to minor
> changes in our unmapper in MMapDirectory: An instanceof check and casting if
> possible.
> I opened this issue to keep track and implement the changes as soon as
> possible, so people will have working unmapping when java 9 comes out.
> Current Lucene versions will no longer work with Java 9.
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