Re: [classad-users] Dependencies and repetitions in DAGMan

[Alain Roy <roy@xxxxxxxxxxx>]

Hi,

This mailing list is for discussion about the Condor ClassAd library,  
not general Condor issues. You're better off with condor-users. That  
said, I'll try to answer your questions.
> 1. In a DAG input file, it seems that the name of the submit  
> description
>   filenames given to jobs constitute a unique name when expressing
>   dependencies. That was a mouthfull, so here's an example:
>
>   # Filename: B.dag
>   JOB A A.condor DONE
>   JOB B B.condor
>   PARENT A CHILD B
>
>   So, my understanding is that job B will only run once all jobs
>   described by A.condor are completed. For example, lets say the
>   following submit files were enqueued:
>
>   1. A.condor
>   2. B.dag
>   3. A.condor
>
>   Then, would B.dag only run once #1 is completed or once all
>   submits matching A.condor are completed or is there something
>   I don't understand?
I'm not sure I follow, but...

a) DAGMan expects that A.condor will submit exactly one job--no more,  
no less. So your question about "all submits matching A.condor"  
doesn't quite make sense.
b) DAGMan doesn't look at other jobs that have been submitted, it only  
tracks the jobs it's submitted. So DAGMan will only submit A.condor,  
then B.condor. If A or B was separately submitted, DAGMan won't notice  
or pay attention. It submits the jobs, then tracks them by their job id.
> 2. Is there a way to express either a submit description file or a DAG
>   input file so that an executable is run on each node in a cluster
>   only once? If not, must I enqueue a submit description file for
>   each node with something like:
>
>   requirements = other.hostname == 'foo'
>
>   And so forth for each host. (Note that "hostname" probably isn't
>   part of ClassAd, but I mean anything that uniquely identifies each
>   node in a cluster)
There's no easy way to say "once for each host". Even ignoring the  
fact that the list of hosts is dynamic, there isn't a way. I would  
probably script this: make a script that takes a list of hostnames (or  
discovers it), then submits one job for each host with requirements  
set to run there. You could cluster them in a DAG, if you like, though  
it's not necessary.
> 3. Would it be possible to remove a resource provider (a machine) from
>   a cluster but only once the current jobs have completed as well as
>   all the other dependent jobs as defined by the pending DAG input
>   files? For example, here's an example:
>
>   # Filename: A.dag
>   JOB A A.condor
>   JOB B B.condor
>   PARENT A CHILD B
>
>   So, if a node is in the middle of running job A, I would like to be
>   notified somehow when job B has completed. However, I don't  
> necessarily
>   want to hard code that I'm waiting for job B to complete, I would  
> rather
>   express abstractly: tell me when the current jobs and dependents  
> have
>   completed.
I'm a bit confused what you're asking for, but you can tell Condor to  
turn off on a machine by using "condor_off -peaceful". It will wait  
for the running jobs to finish. Make sense?
This is outside of DAGMan--I'm a bit confused by how you're combining  
DAGMan with removing machines from a cluster.
-alain