DRMAA (Distributed Resource Management Application API) appears to be an open API that describes a specification for submission and management of work submitted to some grid/cluster. If your scheduler is DRMAA compliant, my guess would be that using
--drmaa flag will afford you the additional controls exposed by that API.
As mentioned in your question with DRMAA support, a Ctrl+C on one's console would be passed on to the grid to kill or stop submitted jobs. A task that would otherwise require use of the
qdel command on
Sun Grid Engine, for example.
I could see why the suggestion would be to enable
--drmaa where possible as it's likely to expose functionality (such as control of jobs, and availability of logs and errors) that makes the submission and management of jobs a little easier for you and
snakemake. Perhaps someone with
snakemake experience can explain a little more, but I hope this helps?
For what it's worth, I use Sun Grid Engine without DRMAA and it's quite a pain to get good information out of
qstat, and its
qacct log format is quite possibly the worst file format I have ever encountered. I suspect DRMAA provides a nice (or at least more reasonable) API for
snakemake (and others) to get at this information more readily.
Under the hood, the flags are parsed by Python's
argparse module in the
__init__.py. A mutually exclusive group of options forces a selection of
-c requires you to specify an argument; the command for which to submit a job on your cluster (the example names
--drmaa flag just seems to indicate to
snakemake that DRMAA is to be used, which doesn't change a lot in terms of how the command you run from your console is processed in the
However, when it is time to interface with your scheduler (as specified in
elif statement checks whether you're in some form of cluster mode and the
else catches the case where you've raised the
--drmaa flag instead.
Here's where the magic happens, as now your job is submitted with the
DRMAAExecutor as specified in executors.py, instead of the default executor.
Without investigating much more, I can see that the
DRMAAExecutor features some more class attributes and exposes additional functions when compared to the others.
Hope this is of more use? Again, I've only just looked at the code myself but in lieu of a
snakemake user chiming in, I thought I'd have a nose.