The following script executes the given commands on specified remote hosts in parallel. Notice that default actors corePoolSize parameter has been set to a higher value than the default one, as cpu usage for this script will remain low, actors will mostly wait for remote server results. (jassh.jar executable jar is available here - JASSH project page) 

#!/bin/sh
exec java -jar jassh.jar -deprecation -savecompiled -usejavacp -nocompdaemon "$0" "$@"
!#

import fr.janalyse.ssh._
import util.Properties

if (args.size<2) {
  println("""usage : rexec.scala command [user[:password]@]host[:port] ...""")
  println("""  Of course prefer public key authentication, default behavior if no password is provided """)
  println("""  example : rexec.scala "hostname" 192.168.1.10 toto@192.168.1.11 toto@192.168.1.12:22""")
  System.exit(0)
}

// host | host:port | username@host |username:password@host | username@host:port | ... 
val serverRE="""(?:(\w+)(?:[:](.*))?@)?((?:(?:\d+[.]){3}\d+)|(?:\w+))(?:[:](\d+))?""".r

val cmd2exec=args.head
val servers = args.tail map {
  case serverRE(user, password, host, port) => 
    SSHOptions(
      host     = host,
      username = Option(user).getOrElse(Properties.userName),
      password = SSHPassword(Option(password)),
      port     = Option(port).map(_.toInt).getOrElse(22)
    )
  case notUnderstood => 
    throw new RuntimeException("Couln'd understand remote host description : "+notUnderstood)
}


def rexec(server:SSHOptions, cmd2exec:String):String = 
  SSH.once(server)(_.execute(cmd2exec))
     .split("\n")
     .map("%8s@%-16s: %s".format(server.username, server.host, _))
     .mkString("\n")
 
  
var sys=new scala.sys.SystemProperties()
sys+="actors.corePoolSize"->"25"


import actors.Actor._
val caller=self
for(server <- servers) actor { caller ! rexec(server, cmd2exec) }
for(_ <- servers) receive {case msg => println(msg) }

usage example :


$ ./rexec.scala "uname -r" test@127.0.0.1  test:testtest@192.168.1.200 
    test@127.0.0.1       : 3.2.1-gentoo-r2
    test@192.168.1.200   : 3.2.0-2-486

From what I've read, scala 2.10 will provide better solutions to tune threads pool, will update this post later.