Fat jar with AppCDS

[Ioi Lam]

Hi Volker,

Thank you so much for writing the tool. We have written some internal 
tools that work similarly. As you said, the current interface is awkward 
(because it's experimental). I have some ideas for how to improve 
support for custom loaders in CDS, and I'll send out a separate mail for 
discussion.

I have made a small patch your cl4cds tool to support "fat" JAR files. 
You can find the patch and a test case from:

     http://cr.openjdk.java.net/~iklam/jdk11/fatjarcds/

It basically extract all entries like

jar:file:/jdk/tmp/test-1.0-SNAPSHOT.jar!/BOOT-INF/lib/validation-api-2.0.1.Final.jar!/

into a local file

     ./tmp/BOOT-INF/lib/validation-api-2.0.1.Final.jar

and read from this location during archive dumping.


Yumin, could you try it out and see if it works for you?

Thanks
- Ioi


On 4/24/18 11:14 PM, yumin qi wrote:
> Hi, Volker
>
>   Thanks! I will try your tool.
>
> Yumin
>
> On Tue, Apr 24, 2018 at 5:42 PM, Volker Simonis 
> <volker.simonis at gmail.com <mailto:volker.simonis at gmail.com>> wrote:
>
>     Hi Yumin,
>
>     your right with your observation. For applications like Tomcat or
>     Eclipse you can currently usually only share about 20%-30% of the
>     application classes, even with AppCDS.
>
>     To overcome this problem I wrote a small tool called "cl4cds" (i.e.
>     class list for CDS) which can be used to generate a classlist out of
>     the "Xlog:class+load" output. Unfortunately this is currently an
>     extra, off-line step which should obviously be integrated right into
>     HotSpot. But for the time being it allows you to take advantage of
>     AppCDS for custom classloaders and share a much bigger amount of
>     classes even for application server scenarios.
>
>     Regards,
>     Volker
>
>     [1] https://github.com/simonis/cl4cds
>     <https://github.com/simonis/cl4cds>
>
>     On Tue, Apr 24, 2018 at 2:49 AM, yumin qi <yumin.qi at gmail.com
>     <mailto:yumin.qi at gmail.com>> wrote:
>     > Hi,Ioi
>     >
>     >   There are some applications with fat jar, that is, like web
>     jars, are
>     > loaded by its own class loaders, are not dumped when run with
>     current mode.
>     > AppCDS can dump the jars in path and loaded by App class loader,
>     but it
>     > does not dump the classes loaded by the class loader "in the
>     jars", which
>     > are loaded in runtime.
>     >
>     >   Do you have any plan to work on this issue? The classes loaded
>     during
>     > runtime are NOT generated classes, they are just designed this
>     way and
>     > stored in other jar files(fat).
>     >
>     >   We are working on the issue, so if you have recommendation or
>     you already
>     > worked on it please let me know.
>     >
>     > Thanks
>     > Yumin
>
>