[DRMAA-WG] DRMAA-C binding comments

[Andreas.Haas at Sun.COM]

Hi Jose,

On Tue, 5 Sep 2006, Jose R. Valverde wrote:

> I'm working on a DRMAA-C binding for EGEE (currently LCG2, and afterwards
> gLite).

Glad to hear this.

> In the process I've noted some noteworthy features in the C binding
> specification.
>
> I guess this has been already noted before, so please do forgive me if it is
> a repetition. I've tried to check the list archives, but it's proving a more
> cumbresome task than I find desirable (or manageable within my timeframe).

Your comments are absolutely welcome. I encountered we dealt already 
with some of them, but we failed to update the C binding spec or at 
least file related items to Grid Forge.

> So, these are some comments to the published standard for the C binding (I
> may send other messages as I procceed with the binding):
>
> Section 4
> =========
>> into an application at run time. An application SHALL NOT be required to directly load more than
>> one library in order to use a DRMAA implementation. The name by which the run time linker will
>  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> 	This requirement actually precludes making the library multithread-
> safe, since that requires awareness of threads and therefore requires linking
> with the pthreads library (-lpthread).

No. It is possible to make a -lpthread shared dependency integral part 
of the DRMAA library. Details how to achieve this can be found under

     http://www.ggf.org/mail_archive/drmaa-wg/2006/05/msg00012.html

also when you follow the discussion under

     http://gridengine.sunsource.net/servlets/BrowseList?list=users&by=thread&from=12304

you see that hiding the -lphtread dependency works on all OS platforms
except on FreeBSD due to a bug.

> 	It is arguable if this should be done by the user and not DRMAA,
> but then Section 2.2 of the DRMAA specification (GFD.022) states
>
>> 2.2    Thread Safety
>> The authors expect that developers will link to a DRMAA library from serial and multithreaded
>> codes; hence it is RECOMMENDED a DRMAA library be thread-safe, and allow a multithreaded
>> application to use DRMAA interfaces without any explicit synchronization among the application
>> threads. It is RECOMMENDED that the DRMAA implementers label their implementations as
>> thread safe if they meet the above criteria. Providers of non thread safe DRMAA
>
> This leads to an inconsistency and an imposibility to code the C-binding API as
> described. I suggest changing the C-binding API documentation to either relax
> the linking requirements or state that the threads library is an exception.
>
> The reason is, if I have a thread-safe library and use it from a non-threaded
> program it won't be evident that I still need to include -lpthreads anyway. And
> vice-versa, if I have a non-thread safe library and use it on a multi-threaded
> environment, as -lpthread will be linked, I won't realize it is not been used
> by the library and hence it is not thread-safe.

This section depends on the issue above.

> Section 5.1.5
> =============
> 	DRMAA_ERRNO_NO_MORE_ELEMENTS is not included, but it is a required
> return value for the string vector manipulation functions

True. Also note there is a second errno value missing in the published
C DRMAA spec. There is a mail I sent in July 2006 to this mailing
list with the corrected list of errno values. I made this mail 
available as attachement of a corresponding DRMAA C binding issue

     https://forge.gridforum.org/sf/go/artf5569?nav=1

since DRMAA WG mail archieve is still broken.

> Section 5.2
> Section 5.2.[789]
> =================
> 	drmaa_release_*() functions are declared to return void in the
> function prototypes of 5.2, but later defined to return various DRMAA_ERRNO
> values (which would make them 'int').
>
> 	I guess that if one does indeed code them as returning int and
> then ignores their return value as if they were void, it is harmless, but
> still it is an inconsistency to address.

True. I added

     https://forge.gridforum.org/sf/go/artf5570?nav=1

for this.

>
> Section 5.3.1.2
> ===============
> 	A typo on the last return value: should be
> 	DRMAA_ERRNO_ALREADY_ACTIVE_SESSION
> instead of
> 	DRMAA_ERRNO_ERRNO_ALREADY_ACTIVE_SESSION

Thanks. I filed it as

     https://forge.gridforum.org/sf/go/artf5571?nav=1

Regards,
Andreas