Unable to create snapshots with Java modules

[Anton Kozlov]

Hmm, I came up with the pure Java solution [1]. I'm not sure those mark_classpath functions are still actual or required.

[1] https://github.com/openjdk/crac/pull/35

Thanks,
Anton

On 11/29/22 18:36, Nikola Grcevski wrote:
> I found out the issue I had with my directory, I was using a symlinked file, so
> the parent directory doesn't match the st_ino of the file. Perhaps
> there's a much
> better way, but I managed to get things to work with the following addition
> (no symlink support):
> 
> static void mark_classpath_or_dir(FdsInfo *fds, char* cp) {
>    DIR *dir = os::opendir(cp);
>    if (!dir) {
>      mark_classpath_entry(fds, cp);
>      return;
>    }
>    os::closedir(dir);
>    mark_all_in(fds, cp);
> }
> 
> ...
> do_classpaths(mark_classpath_or_dir, &fds, Arguments::get_appmodulepath());
> 
> I also had to make a small change in do_classpaths, at the end instead
> of calling
> mark_classpath_entry, I changed it to call fn(fds, cp).
> 
> On Tue, Nov 29, 2022 at 11:24 AM Nikola Grcevski <grcevski at gmail.com> wrote:
>>
>> Great, thanks!
>>
>> I started looking at it as well, I added
>>
>> arguments.cpp/hpp
>> _java_module_path = new SystemProperty("jdk.module.path", "", true);
>>
>> and in os_linux.cpp
>> do_classpaths(mark_classpath_entry, &fds, Arguments::get_appmodulepath());
>>
>> I was able to make things work if I put the expanded module path directly e.g:
>> --module-path lib/simplemodule-1.0-SNAPSHOT.jar
>>
>> I'm not sure if there's a helper to expand the module path fully with
>> directories, when I tried
>> to create a mark function that handles both directories and files, the
>> directory scan
>> and mark never matches on my app lib directory on this check:
>>
>> if (dent->d_ino == fstat->st_ino)
>>
>> in os_linux::static void mark_all_in(FdsInfo *fds, char* dirpath).
>>
>> Thanks so much for your help.
>> Nikola
>>
>> On Tue, Nov 29, 2022 at 11:11 AM Anton Kozlov <akozlov at azul.com> wrote:
>>>
>>> On 11/29/22 00:04, Nikola Grcevski wrote:
>>>> However, if I try the same thing with the modules usage, the snapshot
>>>> creation fails:
>>>> ~/work/simplemodule$ /<path>/openjdk-17-crac+3_linux-x64/bin/java
>>>> -XX:CRaCCheckpointTo=/tmp/simple --module-path lib --module
>>>> simplemodule/co.elastic.simple.SimpleModule
>>>
>>> Hi Nikola,
>>>
>>> I've reproduced the problem. It seems JDK misses a piece of code for modules that is there for class loaders. It looks easy to fix, I'm looking at this.
>>>
>>> Meanwhile, while you're experimenting, you may disable CheckpointException by -XX:+UnlockExperimentalVMOptions -XX:-CRDoThrowCheckpointException. Of course, it's not recommended for anything beyond experiments :)
>>>
>>> Thanks,
>>> Anton