Improve performance by removing spurious actions

1. Remove a number of time.sleep commands which don't really seem
necessary any longer and which significantly increased the startup
time while parsing the VM list.
2. Handle some variable sets during initialization of the object,
rather than waiting for a management command, enabling...
3. Know when a state change, and the corresponding Libvirt lookup,
is unnecessary due to the target node not matching the current node.
This also removes a number of unremovable errors from Libvirt on the
console which were annoying.

This reduces the total time taken by the VM startup segment (lines
760-762 of Daemon.py) from 17.117s down to 0.976s for 82 VMs.

node-daemon/pvcd/DomainInstance.py

@@ -39,15 +39,17 @@ class DomainInstance(object):
     def __init__(self, domuuid, zk_conn, config, logger, this_node):
         # Passed-in variables on creation
         self.domuuid = domuuid
-        self.domname = zkhandler.readdata(zk_conn, '/domains/{}'.format(domuuid))
         self.zk_conn = zk_conn
         self.config = config
         self.logger = logger
         self.this_node = this_node
 
+        # Get data from zookeeper
+        self.domname = zkhandler.readdata(zk_conn, '/domains/{}'.format(domuuid))
+        self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
+        self.node = zkhandler.readdata(self.zk_conn, '/domains/{}/node'.format(self.domuuid))
+
         # These will all be set later
-        self.node = None
-        self.state = None
         self.instart = False
         self.inrestart = False
         self.inmigrate = False
@@ -185,7 +187,7 @@ class DomainInstance(object):
             return
     
         self.shutdown_vm()
-        time.sleep(1)
+        time.sleep(0.2)
         self.start_vm()
         self.addDomainToList()
 
@@ -291,10 +293,8 @@ class DomainInstance(object):
         if not migrate_ret:
             self.logger.out('Could not live migrate VM; shutting down to migrate instead', state='e', prefix='Domain {}:'.format(self.domuuid))
             self.shutdown_vm()
-            time.sleep(1)
         else:
             self.removeDomainFromList()
-            time.sleep(1)
 
         zkhandler.writedata(self.zk_conn, { '/domains/{}/state'.format(self.domuuid): 'start' })
         self.inmigrate = False
@@ -310,7 +310,7 @@ class DomainInstance(object):
         self.inreceive = True
         self.logger.out('Receiving migration', state='i', prefix='Domain {}:'.format(self.domuuid))
         while True:
-            time.sleep(0.5)
+            time.sleep(1)
             self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
             self.dom = self.lookupByUUID(self.domuuid)
 
@@ -343,10 +343,7 @@ class DomainInstance(object):
     # Main function to manage a VM (taking only self)
     #
     def manage_vm_state(self):
-        # Give ourselves a bit of leeway time
-        time.sleep(0.2)
-
-        # Get the current values from zookeeper (don't rely on the watch)
+        # Update the current values from zookeeper
         self.state = zkhandler.readdata(self.zk_conn, '/domains/{}/state'.format(self.domuuid))
         self.node = zkhandler.readdata(self.zk_conn, '/domains/{}/node'.format(self.domuuid))
 
@@ -442,8 +439,11 @@ class DomainInstance(object):
     # 1. Takes a text UUID and handles converting it to bytes
     # 2. Try's it and returns a sensible value if not
     def lookupByUUID(self, tuuid):
+        # Don't do anything if the VM shouldn't live on this node
+        if self.node != self.this_node.name:
+            return None
+
         lv_conn = None
-        dom = None
         libvirt_name = "qemu:///system"
     
         # Convert the text UUID to bytes
@@ -455,14 +455,14 @@ class DomainInstance(object):
             lv_conn = libvirt.open(libvirt_name)
             if lv_conn == None:
                 self.logger.out('Failed to open local libvirt connection', state='e', prefix='Domain {}:'.format(self.domuuid))
-                return dom
+                return None
         
             # Lookup the UUID
             dom = lv_conn.lookupByUUID(buuid)
     
         # Fail
         except:
-            pass
+            dom = None
     
         # After everything
         finally: