CRIU usage for Java application

Question

So I want to use CRIU to make a snapshot of a JVM process and restore it later. For this purpose I wrote a little program which does nothing more but printing the counter every second:

package some;

public class Fun {
    public static void main(String[] args) throws InterruptedException {
        for(int i = 0; i < Integer.valueOf(args[0]); i++) {
            System.out.println("Counter: "+i);
            Thread.sleep(1000);
        }       
    }   
}

Now when I run the programm $ java some.Fun 3000 the program starts showing me the seconds, so far so good.

Now when I want to store the process with criu, i do $ ps -aux, find the PID of my java process (3503 in this case) and call criu on it $ criu dump -t 3503 -o dump.log --shell-job. After doing so, the terminal with the counter stops counting, prints Killed and seems to terminate.

At this point in the folder where i called criu, i got some dump files which I can use to restore the process $ criu restore -o dump.log --shell-job

When I do so, a new process with a new PID is created, and the counter is starts counting from the moment it stopped, as it is supposed to be. Nice!

However, lets say I kill the process and try using the same dump files to restore the process. If I do this, criu terminates right away with the message Aborted (core dumped). Same happens if I try transfer the files on another machine, with the same java version and try to run it there...

Now my question is: is it supposed to be so? Are we supposed to be able to restore the state just once? Or am I doing something wrong? Thank you in advance!

Radostin Stoyanov · Answer 1 · 2020-10-13T19:29:39.127

You need to disable the perfdata feature of JVM.

$ java -XX:-UsePerfData some.Fun 3000

This will suppresses the creation of the /tmp/hsperfdata_userid directories.

The issue occurs because when CRIU checkpoints a process tree it stores the information for all open file descriptors, and during restore it requires all files to be present (and have the same size).

When you first restored your java application, the temporary hsperfdata files were still there and everything worked, but when you killed your application these temporary files were removed as well.

CRIU usage for Java application

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