[OMPI devel] HOSTNAME environment variable

[Nadia Derbey]

Hi,

I'm wondering whether the HOSTNAME environment variable shouldn't be
handled as a "special case" when the orted daemons launch the remote
jobs. This particularly applies to batch schedulers where the caller's
environment is copied to the remote job: we are inheriting a $HOSTNAME
which is the name of the host mpirun was called from:

I tried to run the following small test (see getenv.c in attachment - it
substantially gets the hostname once through $HOSTNAME, and once through
gethostname(2)):

------------
[derbeyn@pichu0 ~]$ hostname
pichu0
[derbeyn@pichu0 ~]$ salloc -N 2 -p pichu mpirun ./getenv
salloc: Granted job allocation 358789
Processor 0 of 2 on $HOSTNAME pichu0: Hello World
Processor 0 of 2 on host pichu93: Hello World
Processor 1 of 2 on $HOSTNAME pichu0: Hello World
Processor 1 of 2 on host pichu94: Hello World
salloc: Relinquishing job allocation 358789
------------

Shouldn't we be getting the same value when using getenv("HOSTNAME") and 
gethsotname()?
Applying the following small patch, we actually do.

Regards,
Nadia

--------------

Do not propagate the HOSTNAME environment variable on remote hosts

diff -r 4ab256be2a17 orte/orted/orted_main.c
--- a/orte/orted/orted_main.c   Wed Jan 20 16:45:07 2010 +0100
+++ b/orte/orted/orted_main.c   Fri Jan 22 14:54:02 2010 +0100
@@ -299,12 +299,17 @@ int orte_daemon(int argc, char *argv[])
      */
     orte_launch_environ = opal_argv_copy(environ);

+    /*
+     * Set HOSTNAME to the actual hostname in order to avoid propagating
+     * the caller's HOSTNAME.
+     */
+    gethostname(hostname, 100);
+    opal_setenv("HOSTNAME", hostname, true, &orte_launch_environ);

     /* if orte_daemon_debug is set, let someone know we are alive right
      * away just in case we have a problem along the way
      */
     if (orted_globals.debug) {
-        gethostname(hostname, 100);
         fprintf(stderr, "Daemon was launched on %s - beginning to 
initialize\n", hostname);
     }


#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <mpi.h>


int main(int argc, char **argv)
{
    char *env_hostname;
    char hostname[255];
    int myrank, size;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    env_hostname = getenv("HOSTNAME");
    if (NULL != env_hostname) {
        printf("Processor %d of %d on $HOSTNAME %s: Hello World\n",
               myrank, size, env_hostname);
    } else {
        printf("Processor %d of %d on $HOSTNAME NULL: Hello World\n",
               myrank, size);
    }
    if (0 == gethostname(hostname, 255)) {
        printf("Processor %d of %d on host %s: Hello World\n",
               myrank, size, hostname);
    }

    MPI_Finalize();

    exit(0);
}