IntelMPI first execution crashes, mpd process on remote host does not exit

IntelMPI first execution crashes, mpd process on remote host does not exit

I found during my test that in case the first execution crashes, a mpd.py process on remote host does not exit automatically.

Here're the steps, assume you have two host host1 and host2

1.
start a mpd ring on the two hosts under normal user:

export MPD_CON_EXT=1234

mpdboot -n 2 -f $hfile

in which hfile contains two hosts host1 and host2

2.
on host1, kill -9 the mpd process and all intel mpi process in one shot

3.
on host2 (remote host), you see a left over mpd.py process

Is there a way to make the mpd ring exit by itself in a clean way?

Thanks.

- Jin

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Hi Jin,

Could you try out a script like:

export MPD_CON_EXT=1234
mpdboot -n 2 -f $hfile #(might be you need -r ssh)
mpiexec -n NNN ./my_application
mpdcleanup -a

I hope it works.

Regards!
Dmitry

Hi Dmitry,

if first node crashes, I would not be able to know MPD_CON_EXT on other nodes.

mpdcleanup -a may terminates other mpd rings which do not include the first node.
The key reason of MPD_CON_EXT is to start up individual mpd ring to each applications.

So it seems like mpdcleanup -a may not work for me.

What Iexpect is that mpd ring terminates itself automatically if one mpd in the ring
stops responding. and each mpd process should exit in a clean way, no left over processes.

Thanks.

- Jin

Hi Jin,

Seems I didn't understand the problem.
If you need to run each application with individual ring you can use 'mpirun' utility. It uses unique MPD_CON_EXT internally, creates mpd ring and destroys this mpd ring when application is finished. All mpds related to this task will be killed automatically.
Other mpds will not be affected.

If you create your own MPD_CON_EXT and start new ring using 'mpdboot' mpds will live until you kill them. They will NOT be killed automatically.
If one mpd stops responding your mpd ring will be one node smaller.

Would you like to change existing behaviour?

Regards!
Dmitry

Dmitry.

I checked mpirun, it's script and it does the same thing:
construct a host file, set a unique MPD_CON_EXT, and then call mpdboot command.
In this case, if the first host crashes (where mpirun is running),
I'd assume I can still see the same problem I described: left over mpd.py processes
on other hosts. Is that right? Is that a behavior by design?

Thanks!

424 # Start an exclusive MPD ring by setting an unique MPD_CON_EXT variable

425 if [ -n "$ENVIRONMENT" -a -n "$QSUB_REQID" -a -n "$QSUB_NODEINF" ] ; then

426 export MPD_CON_EXT=$QSUB_REQID # Called under Fujitsu NQS

427 else

428 export MPD_CON_EXT=`date +%y%m%d.%H%M%S`

429 fi

430 #echo "mpdboot -n $np_boot $hosts_opt $other_mpdboot_opt"

431 #echo "HOSTFILE:"

432 #cat $hosts_file

433 mpdboot -n $np_boot $hosts_opt $other_mpdboot_opt

434 #mpdtrace

Hi Jin,

If you are talking about abnormal termination than 'yes' - mpirun will not be able to stop all mpds and mpds don't know that they need to be killed.
According to existing logic a node (mpd) can disappear from a ring at any time - no problem.

In version 4.0 of the Intel MPI library there is an experimental Process Manager called Hydra.
You can run 'mpiexec.hydra' instead of 'mpirun' (all the rest parameters are the same). All processes running on remote nodes should be killed automatically in case of any abnormal termination of the application. Let's try.

Regards!
Dmitry

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