Deregister a launcher when removed from config

We were depending only on the ephemeralness of launcher registration
nodes to indicate when a provider goes away. That only works when
nodepool-launcher is restarted since the ZK connection is shared
among all provider threads. This adds an API method to manually
deregister and modifies a test to ensure it works.

Change-Id: I363fc4a67a83b49b515b963f5d5accdcf1cb758c

nodepool/launcher.py

@@ -381,6 +381,7 @@ class PoolWorker(threading.Thread, stats.StatsReporter):
         '''
         self.log.info("%s received stop" % self.name)
         self.running = False
+        self.zk.deregisterLauncher(self.launcher_id)
         self.stop_event.set()
 
 

nodepool/tests/unit/test_launcher.py

@@ -1482,6 +1482,9 @@ class TestLauncher(tests.DBTestCase):
         self.waitForNodes('fake-label')
         self.assertEqual(2, len(pool._pool_threads))
 
+        # We should have two pool workers registered
+        self.assertEqual(2, len(self.zk.getRegisteredLaunchers()))
+
         self.replace_config(configfile, 'launcher_two_provider_remove.yaml')
 
         # Our provider pool thread count should eventually be reduced to 1
@@ -1493,6 +1496,9 @@ class TestLauncher(tests.DBTestCase):
             except AssertionError:
                 pass
 
+        # We should have one pool worker registered
+        self.assertEqual(1, len(self.zk.getRegisteredLaunchers()))
+
     def test_failed_provider(self):
         """Test that broken provider doesn't fail node requests."""
         configfile = self.setup_config('launcher_two_provider_max_1.yaml')

nodepool/zk.py

@@ -1508,9 +1508,10 @@ class ZooKeeper(object):
         '''
         Register an active node launcher.
 
-        The launcher is automatically de-registered once it terminates or
-        otherwise disconnects from ZooKeeper. It will need to re-register
-        after a lost connection. This method is safe to call multiple times.
+        The launcher is de-registered when the launcher process terminates or
+        otherwise disconnects from ZooKeeper, or via deregisterLauncher().
+        It will need to re-register after a lost connection. This method is
+        safe to call multiple times.
 
         :param Launcher launcher: Object describing the launcher.
         '''
@@ -1528,6 +1529,18 @@ class ZooKeeper(object):
                                makepath=True, ephemeral=True)
             self.log.debug("Registered launcher %s", launcher.id)
 
+    def deregisterLauncher(self, launcher_id):
+        '''
+        Deregister an active node launcher.
+
+        :param str launcher_id: ID of the launcher to deregister.
+        '''
+        path = self._launcherPath(launcher_id)
+        try:
+            self.client.delete(path, recursive=True)
+        except kze.NoNodeError:
+            pass
+
     def getRegisteredLaunchers(self):
         '''
         Get a list of all launchers that have registered with ZooKeeper.