How to Use posix_spawn() in Java

Question

I've inherited a legacy application that uses ProcessBuilder.start() to execute a script on a Solaris 10 server.

Unfortunately, this script call fails due to a memory issue, as documented here

Oracle's recommendation is to use posix_spawn() since, under the covers, ProcessBuilder.start() is using fork/exec.

I have been unable to find any examples (e.g., how to call "myScript.sh")

using posix_spawn() in Java, or even what are the packages that are required.

Could you please, point me to a simple example on how to use posix_spawn() in Java?

Answer 1

Recent version of Java 7 and 8 support posix_spawn internally.

command line option

-Djdk.lang.Process.launchMechanism=POSIX_SPAWN

or enable at runtime

System.setProperty("jdk.lang.Process.launchMechanism", "POSIX_SPAWN");

I'm a little confused as to which Java version/OS combinations have this enabled by default, but I'm sure you could test and find out pretty quickly whether setting this option makes a difference.

For reference, to go back to the old fork method simply use

-Djdk.lang.Process.launchMechanism=fork

To prove whether this option is respected in your JVM version use

-Djdk.lang.Process.launchMechanism=dummy

and you will get an error next time you exec. This way you know the JVM is receiving this option.

Answer 2

An alternative, which does not require JNI, is to create a separate "process spawner" application. I would probably have this application expose an RMI interface, and create a wrapper object that is a drop-in replacement for ProcessBuilder.

You might also want to consider having this "spawner" application be the thing that starts your legacy application.