103 lines
3.2 KiB
Python
103 lines
3.2 KiB
Python
import logging
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import time
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from platypush.backend import Backend
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from platypush.context import get_plugin
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from platypush.message import Message
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from platypush.message.event.kafka import KafkaMessageEvent
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class KafkaBackend(Backend):
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"""
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Backend to interact with an Apache Kafka (https://kafka.apache.org/)
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streaming platform, send and receive messages.
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Requires:
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* **kafka** (``pip install kafka-python``)
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"""
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_conn_retry_secs = 5
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def __init__(self, server='localhost:9092', topic='platypush', **kwargs):
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"""
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:param server: Kafka server name or address + port (default: ``localhost:9092``)
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:type server: str
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: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")
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:type topic: str
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"""
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super().__init__(**kwargs)
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self.server = server
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self.topic_prefix = topic
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self.topic = self._topic_by_device_id(self.device_id)
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self.producer = None
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self.consumer = None
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# Kafka can be veryyyy noisy
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logging.getLogger('kafka').setLevel(logging.ERROR)
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def _on_record(self, record):
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if record.topic != self.topic: return
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msg = record.value.decode('utf-8')
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is_platypush_message = False
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try:
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msg = Message.build(msg)
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is_platypush_message = True
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except Exception as e:
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self.logger.debug(str(e))
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self.logger.info('Received message on Kafka backend: {}'.format(msg))
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if is_platypush_message:
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self.on_message(msg)
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else:
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self.on_message(KafkaMessageEvent(msg=msg))
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def _topic_by_device_id(self, device_id):
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return '{}.{}'.format(self.topic_prefix, device_id)
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def send_message(self, msg, **kwargs):
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target = msg.target
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kafka_plugin = get_plugin('kafka')
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kafka_plugin.send_message(msg=msg,
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topic=self._topic_by_device_id(target),
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server=self.server)
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def on_stop(self):
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super().on_stop()
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try:
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if self.producer:
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self.producer.flush()
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self.producer.close()
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if self.consumer:
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self.consumer.close()
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except Exception as e:
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self.logger.warning('Exception occurred while closing Kafka connection')
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self.logger.exception(e)
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def run(self):
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from kafka import KafkaConsumer
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super().run()
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self.consumer = KafkaConsumer(self.topic, bootstrap_servers=self.server)
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self.logger.info('Initialized kafka backend - server: {}, topic: {}'
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.format(self.server, self.topic))
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try:
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for msg in self.consumer:
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self._on_record(msg)
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if self.should_stop(): break
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except Exception as e:
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self.logger.warning('Kafka connection error, reconnecting in {} seconds'.
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format(self._conn_retry_secs))
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self.logger.exception(e)
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time.sleep(self._conn_retry_secs)
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# vim:sw=4:ts=4:et:
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