diff --git a/ceilometer/collector/service.py b/ceilometer/collector/service.py
index 033f1f0a2..9da8b9603 100644
--- a/ceilometer/collector/service.py
+++ b/ceilometer/collector/service.py
@@ -168,6 +168,16 @@ class CollectorService(rpc_service.Service):
         )
 
     def _setup_subscription(self, ext, *args, **kwds):
+        """Connect to message bus to get notifications
+
+        Configure the RPC connection to listen for messages on the
+        right exchanges and topics so we receive all of the
+        notifications.
+
+        Use a connection pool so that multiple collector instances can
+        run in parallel to share load and without competing with each
+        other for incoming messages.
+        """
         handler = ext.obj
         ack_on_error = cfg.CONF.collector.ack_on_event_error
         LOG.debug('Event types from %s: %s (ack_on_error=%s)',
@@ -188,12 +198,22 @@ class CollectorService(rpc_service.Service):
                                   (topic, exchange_topic.exchange))
 
     def record_metering_data(self, context, data):
+        """RPC endpoint for messages we send to ourself
+
+        When the notification messages are re-published through the
+        RPC publisher, this method receives them for processing.
+        """
         self.dispatcher_manager.map(self._record_metering_data_for_ext,
                                     context=context,
                                     data=data)
 
     def process_notification(self, notification):
-        """Make a notification processed by an handler."""
+        """RPC endpoint for notification messages
+
+        When another service sends a notification over the message
+        bus, this method receives it. See _setup_subscription().
+
+        """
         LOG.debug('notification %r', notification.get('event_type'))
         self.notification_manager.map(self._process_notification_for_ext,
                                       notification=notification)
@@ -250,9 +270,22 @@ class CollectorService(rpc_service.Service):
 
     @staticmethod
     def _record_metering_data_for_ext(ext, context, data):
+        """Wrapper for calling dispatcher plugin when a sample arrives
+
+        When a message is received by record_metering_data(), it calls
+        this method with each plugin to allow it to process the data.
+
+        """
         ext.obj.record_metering_data(context, data)
 
     def _process_notification_for_ext(self, ext, notification):
+        """Wrapper for calling pipelines when a notification arrives
+
+        When a message is received by process_notification(), it calls
+        this method with each notification plugin to allow all the
+        plugins process the notification.
+
+        """
         with self.pipeline_manager.publisher(context.get_admin_context()) as p:
             # FIXME(dhellmann): Spawn green thread?
             p(list(ext.obj.to_samples(notification)))