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from airflow.sensors.base_sensor_operator import BaseSensorOperator
from airflow.utils.decorators import apply_defaults
from airflow.contrib.hooks.redis_hook import RedisHook
[docs]class RedisPubSubSensor(BaseSensorOperator):
"""
Redis sensor for reading a message from pub sub channels
"""
[docs] template_fields = ('channels',)
@apply_defaults
def __init__(self, channels, redis_conn_id, *args, **kwargs):
"""
Create a new RedisPubSubSensor and subscribe to the channels
:param channels: The channels to be subscribed to (templated)
:type channels: str or list of str
:param redis_conn_id: the redis connection id
:type redis_conn_id: str
"""
super(RedisPubSubSensor, self).__init__(*args, **kwargs)
self.channels = channels
self.redis_conn_id = redis_conn_id
self.pubsub = RedisHook(redis_conn_id=self.redis_conn_id).get_conn().pubsub()
self.pubsub.subscribe(self.channels)
[docs] def poke(self, context):
"""
Check for message on subscribed channels and write to xcom the message with key ``message``
An example of message ``{'type': 'message', 'pattern': None, 'channel': b'test', 'data': b'hello'}``
:param context: the context object
:type context: dict
:return: ``True`` if message (with type 'message') is available or ``False`` if not
"""
self.log.info('RedisPubSubSensor checking for message on channels: %s', self.channels)
message = self.pubsub.get_message()
self.log.info('Message %s from channel %s', message, self.channels)
# Process only message types
if message and message['type'] == 'message':
context['ti'].xcom_push(key='message', value=message)
self.pubsub.unsubscribe(self.channels)
return True
return False