Set batch=False in OVSSwitch for low-level API

If you try to use the low-level API, you are probably
not going to call batchStartup()! So, we set batch=False
by default. This means that buildFromTopo() needs to set
it to True, so we add a bit of irritatingly complex machinery
to allow this to happen. The good fallout of this is that
now customConstructor() returns a real subclass, not simply
a constructor function! We also detect errors where people
are incorrectly attempting to give parameters to a lambda
function - since none of our lambdas accept parameters!!

Note that this is a bit like functools.partial for classes -
it would be nice if functools had a true subclassing function.

mininet/net.py

@@ -414,7 +414,12 @@ class Mininet( object ):
 
         info( '\n*** Adding switches:\n' )
         for switchName in topo.switches():
-            self.addSwitch( switchName, **topo.nodeInfo( switchName) )
+            # A bit ugly: add batch parameter if appropriate
+            params = topo.nodeInfo( switchName)
+            cls = params.get( 'cls', self.switch )
+            if hasattr( cls, 'batchStartup' ):
+                params.setdefault( 'batch', True )
+            self.addSwitch( switchName, **params )
             info( switchName + ' ' )
 
         info( '\n*** Adding links:\n' )

mininet/node.py

@@ -1058,7 +1058,7 @@ class OVSSwitch( Switch ):
 
     def __init__( self, name, failMode='secure', datapath='kernel',
                   inband=False, protocols=None,
-                  reconnectms=1000, stp=False, batch=True, **params ):
+                  reconnectms=1000, stp=False, batch=False, **params ):
         """name: name for switch
            failMode: controller loss behavior (secure|open)
            datapath: userspace or kernel mode (kernel|user)
@@ -1067,7 +1067,7 @@ class OVSSwitch( Switch ):
                       Unspecified (or old OVS version) uses OVS default
            reconnectms: max reconnect timeout in ms (0/None for default)
            stp: enable STP (False, requires failMode=standalone)
-           batch: enable batch startup (True)"""
+           batch: enable batch startup (False)"""
         Switch.__init__( self, name, **params )
         self.failMode = failMode
         self.datapath = datapath

mininet/util.py

@@ -536,19 +536,28 @@ def customConstructor( constructors, argStr ):
         raise Exception( "error: %s is unknown - please specify one of %s" %
                          ( cname, constructors.keys() ) )
 
-    def customized( name, *args, **params ):
+    if not newargs and not kwargs:
-        "Customized constructor, useful for Node, Link, and other classes"
+        return constructor
+
+    if not isinstance( constructor, type ):
+        raise Exception( "error: invalid arguments %s" % argStr )
+
+    # Return a customized subclass
+    cls = constructor
+    class CustomClass( cls ):
+        "Customized subclass, useful for Node, Link, and other classes"
+        def __init__( self, name, *args, **params ):
             params = params.copy()
             params.update( kwargs )
             if not newargs:
-            return constructor( name, *args, **params )
+                return cls.__init__( self, name, *args, **params )
             if args:
-            warn( 'warning: %s replacing %s with %s\n' % (
+                warn( 'warning: %s replacing %s with %s\n' %
-                  constructor, args, newargs ) )
+                      ( constructor, args, newargs ) )
-        return constructor( name, *newargs, **params )
+                return cls.__init__( self, name, *newargs, **params )
 
-    customized.__name__ = 'customConstructor(%s)' % argStr
+    CustomClass.__name__ = '%s%s' % ( cls.__name__, kwargs )
-    return customized
+    return CustomClass
 
 def buildTopo( topos, topoStr ):
     """Create topology from string with format (object, arg1, arg2,...).