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https://issues.apache.org/jira/browse/LUCENE-6989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15136941#comment-15136941
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Uwe Schindler edited comment on LUCENE-6989 at 2/8/16 1:32 PM:
---------------------------------------------------------------
Second version of the patch - a complete rewrite:
- Fail early by checking everything early!
- Implement this with MethodHandles (reflection is only needed for the single
setAccessible() place: MethodHandles allow to do any access checks at linking
time, not runtime),
- Also do the SecurityManager checks early (for the runable variant)
This patch implements 3 variants of unmapping:
- Java 7/8 using sun.misc.Cleaner
- Java 9 variant 1 using Runnable (public API, we just need to get reference to
the cleaner with setAccessible)
- Java 9 proposed change to remove private cleaner completely and replace by
java.lang.ref.Cleaner.Cleanable (public API, we just need to get reference to
the cleaner with setAccessible)
was (Author: thetaphi):
Second version of the patch - a complete rewrite:
- Fail early by checking everything early
- Implement this with MethodHandles (reflection is only needed for the single
setAccessible) place
- Also do the SecurityManager checks early
This patch implements 3 variants of unmapping:
- Java 7/8 using sun.misc.Cleaner
- Java 9 variant 1 using Runnable (public API, we just need to get reference to
the cleaner with setAccessible)
- Java 9 proposed change to remove private cleaner completely and replace by
java.lang.ref.Cleaner.Cleanable (public API, we just need to get reference to
the cleaner with setAccessible)
> 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
> Priority: Critical
> Attachments: 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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