remus: blackhole replication target

The new --null option allows one to test and play with just the
memory checkpointing and network buffering aspect of remus, without
the need for a second host. The disk is not replicated. All replication
data is sent to /dev/null. This option is pretty handy when a user
wants to see the page churn for his workload or observe the latency hit
though the latter will not be accurate.

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/python/xen/remus/save.py

@@ -95,6 +95,12 @@ class MigrationSocket(_proxy):
         self.sock = sock
         super(MigrationSocket, self).__init__(fd)
 
+class NullSocket(_proxy):
+    def __init__(self, address):
+        filedesc = os.open('/dev/null', 0666)
+        fd = os.fdopen(filedesc, 'w+')
+        super(NullSocket, self).__init__(fd)
+
 class Keepalive(object):
     "Call a keepalive method at intervals"
     def __init__(self, method, interval=0.1):