Hi Rayson, Thanks for your email. What I meant by pure Java in this case was a DRMAA library that does not rely on setting the java.library.path to load any compiled C/C++ shared objects. In the implementation I'm working on, I still have to call the Condor binaries (condor_submit, condor_q) in certain places. In this sense, it would work just the like Peter's C implementation, which does the same thing. One could argue that this isn't really "pure" Java since I am relying on the binaries, but what I'm mainly interested in is avoiding JNI and the associated complexity that goes along with it (multi-language issues, deployment issues, etc). Further, there are some scenarios in which JNI usage is problematic. For instance, let's say you want to use the DRMAA library in Tomcat for example. Recent versions of Tomcat had problems with libraries that use JNI (a loading/unloading issue). This may have been fixed in Tomcat 6, but I'm not sure. The other problem I ran into was some issues with methods that were not implemented in the Condor C implementation that became issues for me when trying to run array jobs. Peter mentioned that these have been corrected (thanks Peter!), so I should have another look... -Victor -----Original Message----- From: Rayson Ho [mailto:rayrayson@gmail.com] Sent: Tuesday, September 09, 2008 2:09 PM To: Felix, Victor Cc: drmaa-wg@ogf.org Subject: Re: [DRMAA-WG] Java DRMAA implementation for Condor Victor, (I missed the first part of today's meeting, and only heard the later part of your intro to the condor-jdrmaa project. May be you mentioned something that I am missing here) The condor-jdrmaa SF page says "future versions will reduce the amount of JNI used, so that eventually, a pure Java..." IMO, it is hard to implement a pure Java DRMAA library, as the only way to talk to the Central Manager in Condor, or pbs_server in PBS/PBSPro/Torque, or mbatchd in LSF is via a TCP/IP socket connection, yet each DRM has its own protocol. It's a bit better on the SGE side, as it has JGDI (Java Grid engine Database Interface) and JMX, but it requires running a JVM in the qmaster, and it's not really for DRMAA yet: http://gridengine.sunsource.net/download/workshop10-12_09_07/SGE-WS2007- FutureSunGridEngineCoreEnhancements_SMI_AndySchwierskott.pdf And my question is, what's the benefit of getting a pure Java implementation, and what are the problems that cannot be fixed in the current implementation of using Java wrappers+JNI+C DRMAA? Writing new Java code to talk to the master machine from scratch is a big effort, and doing that for each DRM may introduce compatibility issues -- SGE developers mentioned before that GDI compatibility is not guaranteed across versions. FYI, in 2006 the XGrid DRMAA Summer of Code project uses the Java wrappers+JNI+C DRMAA, and there were a number of things that Ed did to get it to work: http://code.edbaskerville.com/2006/07/11/java-bindings-working/ And you can see the background info here: http://www.ogf.org/pipermail/drmaa-wg/2006-June/000470.html Rayson On 9/2/08, Felix, Victor <vfelix@som.umaryland.edu> wrote:
Hello,
Just wanted to point out that a new project has been set up on SourceForge to provide a Java DRMAA implementation for Condor, which has been missing. It is called Condor-JDRMAA. The current release is simply a wrapper around the C implementation, however future releases will work toward a pure Java implementation...
http://sourceforge.net/projects/condor-jdrmaa/
Best regards,
-Victor
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