Implement notification framework

JIRA: PHAROS-265

The framework can be used by the dashboard and the labs to exchange
notifications about booking events and pod status.

Change-Id: Ibd7cd353c4933f7662d5368182faef8298b85efc
Signed-off-by: maxbr <maxbr@mi.fu-berlin.de>

2 files changed, 104 insertions, 0 deletions

diff --git a/pharos-dashboard/notification_framework/__init__.py b/pharos-dashboard/notification_framework/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/pharos-dashboard/notification_framework/__init__.py
diff --git a/pharos-dashboard/notification_framework/notification.py b/pharos-dashboard/notification_framework/notification.py
new file mode 100644
index 0000000..7d77283
--- /dev/null
+++ b/pharos-dashboard/notification_framework/notification.py
@@ -0,0 +1,104 @@
+import json
+import re
+
+import pika
+
+
+class Notification(object):
+    """
+    This class can be used by the dashboard and the labs to exchange notifications about booking
+    events and pod status. It utilizes rabbitmq to communicate.
+
+    Notifications are associated to an event and to a topic.
+    Events are:
+    [ 'booking_start', 'booking_stop', 'pod_status' ]
+    The topic is usually a POD name, ie:
+    'Intel POD 2'
+    """
+
+    def __init__(self, dashboard_url, verbose=False):
+        self.rabbitmq_broker = dashboard_url
+        self.verbose = verbose
+        self._registry = {}
+
+        self.connection = pika.BlockingConnection(pika.ConnectionParameters(
+            host=self.rabbitmq_broker))
+        self.channel = self.connection.channel()
+
+        self.channel.exchange_declare(exchange='notifications', type='topic')
+
+        self.result = self.channel.queue_declare(exclusive=True)
+        self.queue_name = self.result.method.queue
+
+    def register(self, function, event, regex):
+        """
+        Registers a function to be called for the specified event.
+        :param function: the function to register
+        :param event: the event type
+        :param regex: a regex to specify for wich topics the function will be called. Some
+        possible Expressions can be:
+        'Intel POD 2' : Intel POD 2
+        'Intel POD .*' : All Intel Pods
+        '.*' : All Topics
+        """
+
+        if event not in self._registry:
+            self._registry[event] = [(function, regex)]
+        else:
+            self._registry[event].append((function, regex))
+
+    def receive(self):
+        """
+        Start receiving notifications. This is a blocking operation, if a notification is received,
+        the registered functions will be called.
+        """
+        if self.verbose:
+            print('Start receiving Notifications. Keys: ', self._registry.keys())
+        self._receive_message(self._registry.keys())
+
+    def send(self, event, topic, content):
+        """
+        Send an event notification.
+        :param event: the event type
+        :param topic: the pod name
+        :param content: a JSON-serializable dictionary
+        """
+        message = {
+            'event': event,
+            'topic': topic,
+            'content': content
+        }
+        self._send_message(message)
+
+    def _send_message(self, event):
+        routing_key = event['type']
+        message = json.dumps(event)
+        self.channel.basic_publish(exchange='notifications',
+                                   routing_key=routing_key,
+                                   body=message,
+                                   properties=pika.BasicProperties(
+                                       content_type='application/json'
+                                   ))
+        if self.verbose:
+            print(" [x] Sent %r:%r" % (routing_key, message))
+
+    def _receive_message(self, binding_keys):
+        for key in binding_keys:
+            self.channel.queue_bind(exchange='notifications',
+                                    queue=self.queue_name,
+                                    routing_key=key)
+        self.channel.basic_consume(self._message_callback,
+                                   queue=self.queue_name,
+                                   no_ack=True)
+        self.channel.start_consuming()
+
+    def _message_callback(self, ch, method, properties, body):
+        if self.verbose:
+            print(" [x] Got %r:%r" % (method.routing_key, body))
+        if method.routing_key not in self._registry:
+            return
+        for func, regex in self._registry[method.routing_key]:
+            message = json.loads(body.decode())
+            match = re.match(regex, message['topic'])
+            if match:
+                func(body)