On 10/12/2012 15:26, Ümit Seren wrote:
> Apologies if these question was already answered:
> I did some research but couldn't come up with a definite answer/solution
> for this question/problem.
>
> Let's say I have a simple workflow consisting of 5 steps:
>
> 1.) retrieve data from a database using a REST service
> 2.) storing retrieved data as a csv and staging/copying it to the local
> HPC cluster
> 3.) dispatching first job (SGE) on the cluster for some primary analysis
> 4.) dispatching second job (SGE) on the cluster for secondary analysis
> 5.) staging out the files from cluster
>
> Step 1, 2 are quite easy however I haven an issue with step 3-5.
> So step 4 should only be started once step 3 is finished. However I
> didn't find any native solution in taverna to check if the job is
> finished before I start step 4.
> Furthermore these jobs can run quickly or take some time (depending on
> cluster usage).
> Is there an easy solution to this asynchronous problem?

What do you get back when you submit the job in (3) ?

> I can think of 2 ways how to solve it:
>
> 1.) create a service/nested workflow that checks the output files on the
> cluster
> 2.) create a service/nested workflow that checks the SGE job status (see
> http://www.myexperiment.org/workflows/174.html)

(2) is the normal way to do this. If you look at 
http://www.myexperiment.org/workflows/1768.html it has an example of how 
to do asynchronous calls.

> I know there are also some plugins which might abstract away these
> things (PBS, Unicore).
> But I would be interested in best practices in solving the HPC/Taverna
> interaction.

The looping nested workflow is the normal mechanism. Do you know the 
type of cluster you are running on?

> thanks in advance
> Uemit

Alan



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