Cluster edition prototype: remote nodes and links.

We add a new experimental feature to allow Mininet to run across
a cluster of machines. This is currently implemented via a set
mix-in classes that provide remote nodes that are implemented
via a connection to a remote shell, and remote links which are
tunnels across servers. In this preliminary implementation,
both control and data connections are made via ssh, but this
could change in the future.

A MininetCluster class is provided which allows existing code
to be used with minimal modification - all that is required is
to provide a list of servers to use. A customizable placement
algorithm may also be specified. An experimental CLI subclass
is also provided to make it easier to examine node placement;
status and links commands can also check whether nodes and
tunnels are still running.

Although this is an experimental feature, it does include a
--cluster option to make it convenient to start up a Mininet
simulation over a cluster, and a script to assist with setting
up the prerequisite authentication via ssh key pairs.

The cluster feature is preliminary and missing some obvious
important features, such as parallel startup and multiple tunnel
types, which we hope to add in the future.

bin/mn

@@ -22,7 +22,7 @@ if 'PYTHONPATH' in os.environ:
 
 from mininet.clean import cleanup
 from mininet.cli import CLI
-from mininet.log import lg, LEVELS, info, debug, error
+from mininet.log import lg, LEVELS, info, debug, warn, error
 from mininet.net import Mininet, MininetWithControlNet, VERSION
 from mininet.node import ( Host, CPULimitedHost, Controller, OVSController,
                            NOX, RemoteController, DefaultController,
@@ -35,6 +35,15 @@ from mininet.topolib import TreeTopo, TorusTopo
 from mininet.util import custom, customConstructor
 from mininet.util import buildTopo
 
+from functools import partial
+
+# Experimental! cluster edition prototype
+from mininet.examples.cluster import ( MininetCluster, RemoteHost,
+                                       RemoteOVSSwitch, RemoteLink,
+                                       SwitchBinPlacer, RandomPlacer )
+from mininet.examples.clustercli import DemoCLI as ClusterCLI
+
+PLACEMENT = { 'block': SwitchBinPlacer, 'random': RandomPlacer }
 
 # built in topologies, created only when run
 TOPODEF = 'minimal'
@@ -204,6 +213,14 @@ class MininetRunner( object ):
                          default=False, help="adds a NAT to the topology "
                          "that connects Mininet to the physical network" )
         opts.add_option( '--version', action='callback', callback=version )
+        opts.add_option( '--cluster', type='string', default=None,
+                         metavar='server1,server2...',
+                         help=( 'run on multiple servers (experimental!)' ) )
+        opts.add_option( '--placement', type='choice',
+                         choices=PLACEMENT.keys(), default='block',
+                         metavar='block|random',
+                         help=( 'node placement for --cluster '
+                                '(experimental!) ' ) )
 
         self.options, self.args = opts.parse_args()
 
@@ -226,6 +243,8 @@ class MininetRunner( object ):
     def begin( self ):
         "Create and run mininet."
 
+        global CLI
+        
         if self.options.clean:
             cleanup()
             exit()
@@ -241,8 +260,6 @@ class MininetRunner( object ):
         if self.validate:
             self.validate( self.options )
 
-        inNamespace = self.options.innamespace
-        Net = MininetWithControlNet if inNamespace else Mininet
         ipBase = self.options.ipbase
         xterms = self.options.xterms
         mac = self.options.mac
@@ -251,6 +268,22 @@ class MininetRunner( object ):
         listenPort = None
         if not self.options.nolistenport:
             listenPort = self.options.listenport
+
+        # Handle inNamespace, cluster options
+        inNamespace = self.options.innamespace
+        cluster = self.options.cluster
+        if inNamespace and cluster:
+            print "Please specify --innamespace OR --cluster"
+            exit()
+        Net = MininetWithControlNet if inNamespace else Mininet
+        if cluster:
+            warn( '*** WARNING: Experimental cluster mode!\n'
+              '*** Using RemoteHost, RemoteOVSSwitch, RemoteLink\n' )
+            host, switch, link = RemoteHost, RemoteOVSSwitch, RemoteLink
+            CLI = ClusterCLI
+            Net = partial( MininetCluster, servers=cluster.split( ',' ),
+                           placement=PLACEMENT[ self.options.placement ] )
+
         mn = Net( topo=topo,
                   switch=switch, host=host, controller=controller,
                   link=link,