[crac] RFR: Assume module jars persistent [v2]

[Dan Heidinga]

On Wed, 30 Nov 2022 15:04:51 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Jar files opened by URLClassLoaders are assumed persistent. We need to handle module Jars the same way to prevent CheckpointException as reported by [1] 
>> 
>> [1] https://mail.openjdk.org/pipermail/crac-dev/2022-November/000380.html
>
> Anton Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Move everything to the separate class

Marked as reviewed by heidinga (Committer).

src/java.base/share/classes/jdk/internal/util/jar/PersistentJarFile.java line 56:

> 54:                 zipBeforeCheckpoint.setAccessible(true);
> 55:                 return null;
> 56:             }});

Something to think about that doesn't need to be addressed now:

We may want to lazily cache the accessible reflect Method in a static field to avoid looking it up for each PersistentJarFile.  The value of doing that depends somewhat on how many jars we expect here and how much we care about time spent in checkpoint hooks.

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PR: https://git.openjdk.org/crac/pull/35