Resolve statsd client once at startup

We currently create a new statsd client each time we replace a
provider manager.  This means that if we are unable to resolve
DNS at that time, the new provider may crash due to unhandled
exceptions.

To resolve this, let's adopt the same behavior we have in Zuul
which is to set up the statsd client once at startup and continue
to use the same client object for the life of the process.

This means that operators will still see errors at startup during
a misconfiguration, but any external changes after that will
not affect nodepool.

Change-Id: I65967c71e859fddbea15aee89f6ddae44344c87b

nodepool/driver/statemachine.py

@@ -69,7 +69,8 @@ class StateMachineNodeLauncher(stats.StatsReporter):
     """
 
     def __init__(self, handler, node, provider_config):
-        super().__init__()
+        launcher = handler.pw.nodepool
+        super().__init__(launcher.statsd)
         # Based on utils.NodeLauncher
         logger = logging.getLogger(
             f"nodepool.StateMachineNodeLauncher.{provider_config.name}")

nodepool/driver/utils.py

@@ -51,7 +51,8 @@ class NodeLauncher(threading.Thread,
             describing the provider launching this node.
         '''
         threading.Thread.__init__(self, name="NodeLauncher-%s" % node.id)
-        stats.StatsReporter.__init__(self)
+        launcher = handler.pw.nodepool
+        stats.StatsReporter.__init__(self, launcher.statsd)
         logger = logging.getLogger("nodepool.NodeLauncher")
         request = handler.request
         self.log = get_annotated_logger(logger,

nodepool/launcher.py

@@ -79,7 +79,7 @@ class PoolWorker(threading.Thread, stats.StatsReporter):
         self.launcher_id = "%s-%s-%s" % (socket.getfqdn(),
                                          self.name,
                                          uuid.uuid4().hex)
-        stats.StatsReporter.__init__(self)
+        stats.StatsReporter.__init__(self, nodepool.statsd)
 
     def getPriority(self):
         pool = self.getPoolConfig()
@@ -966,6 +966,7 @@ class StatsWorker(BaseCleanupWorker, stats.StatsReporter):
         self.log = logging.getLogger('nodepool.StatsWorker')
         self.stats_event = threading.Event()
         self.election = None
+        stats.StatsReporter.__init__(self, nodepool.statsd)
 
     def stop(self):
         self._running = False
@@ -977,8 +978,6 @@ class StatsWorker(BaseCleanupWorker, stats.StatsReporter):
 
     def _run(self):
         try:
-            stats.StatsReporter.__init__(self)
-
             if not self._statsd:
                 return
 

nodepool/stats.py

@@ -50,9 +50,9 @@ class StatsReporter(object):
     '''
     Class adding statsd reporting functionality.
     '''
-    def __init__(self):
+    def __init__(self, statsd_client):
         super(StatsReporter, self).__init__()
-        self._statsd = get_client()
+        self._statsd = statsd_client
 
     def recordLaunchStats(self, subkey, dt):
         '''