Initialize coordination during driver init

At the moment, the "init_host" method initializes the distributed
lock mechanism, yet the driver may try to use distributed locks
before that.

For example, the method that reclaims failed over instances is
called by the driver init method, before init_host. While we
can fix this particular call, it's safer that we initialize the
lock mechanism as early as possible.

Change-Id: If361c0f754d3680726762e3126286227bea6f3f3
Related-Bug: #1841777

compute_hyperv/nova/coordination.py

@@ -20,6 +20,7 @@ import uuid
 
 import decorator
 from nova import exception
+from nova import utils
 from oslo_config import cfg
 from oslo_log import log
 from oslo_utils import timeutils
@@ -49,6 +50,7 @@ class Coordinator(object):
         self.started = False
         self.prefix = prefix
 
+    @utils.synchronized(name="coordinator_start")
     def start(self):
         if self.started:
             return

compute_hyperv/nova/driver.py

@@ -120,6 +120,11 @@ class HyperVDriver(driver.ComputeDriver):
         # further driver initialisation.
         self._check_minimum_windows_version()
 
+        # We'll initialize coordination as early as possible, avoiding
+        # the risk of using locks before the mechanism is enabled.
+        if self.use_coordination:
+            coordination.COORDINATOR.start()
+
         super(HyperVDriver, self).__init__(virtapi)
 
         self._hostops = hostops.HostOps()
@@ -158,9 +163,6 @@ class HyperVDriver(driver.ComputeDriver):
         return False
 
     def init_host(self, host):
-        if self.use_coordination:
-            coordination.COORDINATOR.start()
-
         self._serialconsoleops.start_console_handlers()
 
         self._set_event_handler_callbacks()