Add option for only logging events.

Testing Done:

- Unit tests pass.
- Verified that setting --events-only only logged events. Didn't change the launch-configs.
- Verified that not setting --events-only continued existing behavior.

cloud_provider/aws/asg_mm.py

@@ -110,7 +110,7 @@ def is_instance_running(self, instance):
         return True
 
     def not_terminate_instance(self):
-        """ Retures is the ASG set not terminate instance """
+        """ Returns if the ASG is configure to not terminate instances """
         for tag in self.asg_info['Tags']:
             if tag.get('Key') == NOT_TERMINATE_LABEL:
                 return tag['Value']

cloud_provider/aws/aws_minion_manager.py

@@ -49,6 +49,7 @@ def __init__(self, cluster_name, region, refresh_interval_seconds=300, **kwargs)
         self.incluster = kwargs.get("incluster", True)
         self._ac_client = boto_session.client('autoscaling')
         self._ec2_client = boto_session.client('ec2')
+        self._events_only = kwargs.get("events_only", False)
 
         self._refresh_interval_seconds = refresh_interval_seconds
         self._asg_metas = []
@@ -379,6 +380,10 @@ def update_scaling_group(self, asg_meta, new_bid_info):
         logger.info("ASG(%s): New launch-config name: %s",
                     asg_meta.get_name(), new_lc_name)
 
+        if self._events_only:
+            logger.info("Minion-manager configured for only generating events. No changes to launch config will be made.")
+            return
+
         if spot_price is None:
             self.create_lc_on_demand(new_lc_name, launch_config)
         else:
@@ -542,12 +547,15 @@ def schedule_instance_termination(self, asg_meta):
         if len(instances) == 0:
             return
 
-        """
-        Check is ASG set not to terminate instance
-        """
+        # Check if ASG set not to terminate instance
         if asg_meta.not_terminate_instance():
             return
 
+        # Check if the minion-manager is only configured to log events.
+        if self._events_only:
+            logger.info("Minion-manager configured for only generating events. No instances will be terminated.")
+            return
+
         # If the ASG is configured to use "no-spot" or the required tag does not exist,
         # do not schedule any instance termination.
         asg_tag = asg_meta.get_mm_tag()
@@ -630,6 +638,8 @@ def populate_instances(self, asg_meta):
     def minion_manager_work(self):
         """ The main work for dealing with spot-instances happens here. """
         logger.info("Running minion-manager...")
+        if self._events_only:
+            logger.info("Only logging events\n")
         while True:
             try:
                 # Iterate over all asgs and update them if needed.

minion_manager.py

@@ -41,6 +41,8 @@ def run():
                         help="Interval in seconds at which to query AWS")
     parser.add_argument("--cluster-name", required=True,
                         help="Name of the Kubernetes cluster. Get's used for identifying ASGs")
+    parser.add_argument("--events-only", action='store_true', required=False,
+                        help="Whether minion-manager should only emit events and *not* actually do spot/on-demand changes to launch-config")
 
     usr_args = parser.parse_args()
     validate_usr_args(usr_args)
@@ -52,7 +54,7 @@ def run():
     if usr_args.cloud == "aws":
         minion_manager = Broker.get_impl_object(
             usr_args.cloud, usr_args.cluster_name, usr_args.region, int(usr_args.refresh_interval_seconds),
-            aws_profile=usr_args.profile)
+            aws_profile=usr_args.profile, events_only=usr_args.events_only)
         minion_manager.run()
 
 # A journey of a thousand miles ...