Added Kafka plugin

docs/source/events.rst

@@ -10,6 +10,7 @@ Events
     platypush/events/geo.rst
     platypush/events/http.rst
     platypush/events/http.rss.rst
+    platypush/events/kafka.rst
     platypush/events/midi.rst
     platypush/events/music.rst
     platypush/events/path.rst

docs/source/platypush/events/kafka.rst

@@ -0,0 +1,6 @@
+``platypush.message.event.kafka``
+=================================
+
+.. automodule:: platypush.message.event.kafka
+    :members:
+

docs/source/platypush/plugins/kafka.rst

@@ -0,0 +1,6 @@
+``platypush.plugins.kafka``
+===========================
+
+.. automodule:: platypush.plugins.kafka
+    :members:
+

docs/source/plugins.rst

@@ -24,6 +24,7 @@ Plugins
     platypush/plugins/gpio.zeroborg.rst
     platypush/plugins/http.request.rst
     platypush/plugins/ifttt.rst
+    platypush/plugins/kafka.rst
     platypush/plugins/light.rst
     platypush/plugins/light.hue.rst
     platypush/plugins/midi.rst

platypush/backend/kafka/__init__.py

@@ -4,7 +4,10 @@ import time
 
 from kafka import KafkaConsumer, KafkaProducer
 
-from .. import Backend
+from platypush.backend import Backend
+from platypush.context import get_plugin
+from platypush.message import Message
+from platypush.message.event.kafka import KafkaMessageEvent
 
 
 class KafkaBackend(Backend):
@@ -19,9 +22,9 @@ class KafkaBackend(Backend):
 
     _conn_retry_secs = 5
 
-    def __init__(self, server, topic='platypush', **kwargs):
+    def __init__(self, server='localhost:9092', topic='platypush', **kwargs):
         """
-        :param server: Kafka server
+        :param server: Kafka server name or address + port (default: ``localhost:9092``)
         :type server: str
 
         :param topic: (Prefix) topic to listen to (default: platypush). The Platypush device_id (by default the hostname) will be appended to the topic (the real topic name will e.g. be "platypush.my_rpi")
@@ -40,29 +43,31 @@ class KafkaBackend(Backend):
 
     def _on_record(self, record):
         if record.topic != self.topic: return
+        msg = record.value.decode('utf-8')
+        is_platypush_message = False
 
         try:
-            msg = json.loads(record.value.decode('utf-8'))
-        except Exception as e:
-            self.logger.exception(e)
+            msg = Message.build(msg)
+            is_platypush_message = True
+        except:
+            pass
 
-        self.logger.debug('Received message on Kafka backend: {}'.format(msg))
+        self.logger.info('Received message on Kafka backend: {}'.format(msg))
+
+        if is_platypush_message:
             self.on_message(msg)
-
-    def _init_producer(self):
-        if not self.producer:
-            self.producer = KafkaProducer(bootstrap_servers=self.server)
+        else:
+            self.on_message(KafkaMessageEvent(msg=msg))
 
     def _topic_by_device_id(self, device_id):
         return '{}.{}'.format(self.topic_prefix, device_id)
 
     def send_message(self, msg):
         target = msg.target
-        msg = str(msg).encode('utf-8')
-
-        self._init_producer()
-        self.producer.send(self._topic_by_device_id(target), msg)
-        self.producer.flush()
+        kafka_plugin = get_plugin('kafka')
+        kafka_plugin.send_message(msg=msg,
+                                  topic=self._topic_by_device_id(target),
+                                  server=self.server)
 
     def on_stop(self):
         try:

platypush/message/event/kafka.py

@@ -0,0 +1,20 @@
+from platypush.message.event import Event
+
+
+class KafkaMessageEvent(Event):
+    """
+    Kafka message event object. Fired when :mod:`platypush.backend.kafka` receives
+    a new event.
+    """
+
+    def __init__(self, msg, *args, **kwargs):
+        """
+        :param msg: Received message
+        :type msg: str or bytes stream
+        """
+
+        super().__init__(msg=msg, *args, **kwargs)
+
+
+# vim:sw=4:ts=4:et:
+

platypush/plugins/kafka.py

@@ -0,0 +1,70 @@
+import json
+import logging
+import time
+
+from kafka import KafkaProducer
+
+from platypush.context import get_backend
+from platypush.plugins import Plugin, action
+
+
+class KafkaPlugin(Plugin):
+    """
+    Plugin to send messages to an Apache Kafka instance (https://kafka.apache.org/)
+
+    Triggers:
+
+        * :class:`platypush.message.event.kafka.KafkaMessageEvent` when a new message is received on the consumer topic.
+
+    Requires:
+
+        * **kafka** (``pip install kafka-python``)
+    """
+
+    def __init__(self, server=None, **kwargs):
+        """
+        :param server: Default Kafka server name or address + port (format: ``host:port``) to dispatch the messages to. If None (default), then it has to be specified upon message sending.
+        :type server: str
+        """
+
+        super().__init__(**kwargs)
+
+        self.server = '{server}:{port}'.format(server=server, port=port) \
+            if server else None
+
+        self.producer = None
+
+        # Kafka can be veryyyy noisy
+        logging.getLogger('kafka').setLevel(logging.ERROR)
+
+
+    @action
+    def send_message(self, msg, topic, server=None, **kwargs):
+        """
+        :param msg: Message to send - as a string, bytes stream, JSON, Platypush message, dictionary, or anything that implements ``__str__``
+
+        :param server: Kafka server name or address + port (format: ``host:port``). If None, then the default server will be used
+        :type server: str
+        """
+
+        if not server:
+            if not self.server:
+                try:
+                    kafka_backend = get_backend('kafka')
+                    server = kafka_backend.server
+                except:
+                    raise RuntimeError('No Kafka server nor default server specified')
+            else:
+                server = self.server
+
+        if isinstance(msg, dict) or isinstance(msg, list):
+            msg = json.dumps(msg)
+        msg = str(msg).encode('utf-8')
+
+        producer = KafkaProducer(bootstrap_servers=server)
+        producer.send(topic, msg)
+        producer.flush()
+
+
+# vim:sw=4:ts=4:et:
+