Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Development mailing list

Subject: Re: [OMPI devel] Add child to another parent.
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-03-25 13:48:04


On Mar 25, 2011, at 10:48 AM, Hugo Meyer wrote:

> From what you've described before, I suspect all you'll need to do is add some code in orte/mca/odls/base/odls_base_default_fns.c that (a) checks to see if a process in the launch message is being relocated (the construct_child_list code does that already), and then (b) sends the required info to all local child processes so they can take appropriate action.
>
> Failure detection, re-launch, etc. have all been taken care of for you.
>
>
> I looked at the code that you mentioned me and i realize that i have two possible options, that i'm going to share with you to know your opinion.
>
> First of all i will let you know my actual situation with the implementation. As i'm working in a Fault Tolerant system, but using uncoordinated checkpoint i'm taking checkpoints of all my process at different time and storing them on the machine where there are residing, but i also send this checkpoints to another node (lets call it protector), so if this node fails his process should be restarted in the protector that have his checkpoints.
>
> Right now i'm detecting the failure of a process and i know where this process should be restarted, and also i have the checkpoint in the protector. And i also have the child information of course.
>
> So, my options are:
> First Option
>
> I detect the failure, and then i use orte_errmgr_hnp_base_global_update_state() with some modifications and the hnp_relocate but changing the spawning to make a restart from a checkpoint, i suposse that using this, the migration of the process to another node will be updated and everyone will know it, because is the hnp who is going to do this (is this ok?).

This is the option I would use. The other one is much, much more work. In this option, you only have to:

(a) modify the mapper so you can specify the location of the proc being restarted. The resilient mapper module will be handling the restart - if you look at orte/mca/rmaps/resilient/rmaps_resilient.c, you can see the code doing the "replacement" and modify accordingly.

(b) add any required info about your checkpoint to the launch message. This gets created in orte/mca/odls/base/odls_base_default_fns.c, the "get_add_procs_data" function (at the top of the file).

(c) modify the launch code to handle your checkpoint, if required - see the file in (b), the "construct_child" and "launch" functions.

HTH
Ralph

>
> Second Option
>
> Modify one of the spawn variations(probably the remote_spawn from rsh) in the PLM framework and then use the orted_comm to command a remote_spawn in the protector, but i don't know here how to update the info so everyone knows about the change or how this is managed.
>
> I might be very wrong in what I said, my apologies if so.
>
> Thanks a lot for all the help.
>
> Best regards.
>
> Hugo Meyer
>
> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel