Allow a comma separated list of hosts for host_alive detection plugin

Some minor Readme cleanup also.

Change-Id: I7a707f5d566339db1430cbcc7597b95c1df9201c

monasca_setup/README.md

@@ -5,11 +5,5 @@ configuring it to start up on boot.
 
 
 ## Future Considerations
-- A good system for specifying active style checks for configuration would be great. Active style checks are those
-  which run locally but are checking a remote box.
-- The ability to dynamically add detection plugins could be quite valuable. Also it could aid in the active check config.
-    - With the ability to dynamically add I should also include the ability to dynamically remove.
 - A config file with metadata to assist in automatic configuration could be quite valuable, for example user/pass for
   logging into mysql.
-- The current system does not work well in the case of clusters, for example the kafka plugin will end up collecting
-  the same data on each node of a cluster.

monasca_setup/detection/plugins/host_alive.py

@@ -9,26 +9,34 @@ log = logging.getLogger(__name__)
 class HostAlive(monasca_setup.detection.ArgsPlugin):
     """ Setup an host_alive check according to the passed in args.
         Despite being a detection plugin this plugin does no detection and will be a noop without arguments.
-        Expects two space seperated arguments hostname and type. Type can be either 'ssh' or 'ping'. For example:
+        Expects two space seperated arguments hostname and type. Type can be either 'ssh' or 'ping'. hostname
+        can be a comma seperated list of hosts.
+        Examples:
         'monasca-setup -d hostalive -a "hostname=remotebox type=ping"'
+        'monasca-setup -d hostalive -a "hostname=remotebox,remotebox2 type=ssh"'
     """
 
     def _detect(self):
         """Run detection, set self.available True if the service is detected.
         """
         self.available = self._check_required_args(['hostname', 'type'])
+        # Ideally the arg would be called hostnames but leaving it hostname to avoid breaking backward compatibility
 
     def build_config(self):
         """Build the config as a Plugins object and return.
         """
         config = monasca_setup.agent_config.Plugins()
         log.info("\tEnabling {type} host check for {hostname}".format(**self.args))
-        # Since the naming in the args and in the config don't match build_instance is only good for dimensions
-        instance = self._build_instance([])
-        instance.update({'name': "{hostname} {type}".format(**self.args),
-                    'host_name': self.args['hostname'],
-                    'alive_test': self.args['type']})
-        config['host_alive'] = {'init_config': None, 'instances': [instance]}
+        instances = []
+        for hostname in self.args['hostname'].split(','):
+            # Since the naming in the args and in the config don't match build_instance is only good for dimensions
+            instance = self._build_instance([])
+            instance.update({'name': "{0} {1}".format(hostname, self.args['type']),
+                             'host_name': hostname,
+                             'alive_test': self.args['type']})
+            instances.append(instance)
+
+        config['host_alive'] = {'init_config': None, 'instances': instances}
 
         return config