气流http回调传感器

Question

我们的气流实现发送http请求，让服务执行任务。我们希望这些服务在完成任务时让气流知道，所以我们向服务发送一个回调url，他们将在任务完成时调用该url。然而，我似乎找不到回调传感器。人们通常是如何处理的？

Answer 1

Airflow中没有回调或webhook传感器。传感器定义如下：

传感器是一种特定类型的操作员，在满足特定标准之前，它将一直运行。示例包括HDFS或S3中的特定文件、Hive中出现的分区或一天中的特定时间。传感器从BaseSensorOperator派生，并在指定的poke_interval运行poke方法，直到返回True。

这意味着传感器是在外部系统上执行轮询行为的操作员。从这个意义上说，您的外部服务应该有一种方法来保持每个执行任务的状态，无论是内部还是外部，这样轮询传感器就可以检查该状态。

通过这种方式，您可以使用airflow.operators.HttpSensor来轮询HTTP端点，直到满足条件。或者更好的是，编写自己的自定义传感器，让您有机会进行更复杂的处理并保持状态。

否则，如果服务在存储系统中输出数据，则可以使用例如轮询数据库的传感器。我相信你已经明白了。

我将附上一个自定义运算符示例，该示例是我为与ApacheLivyneneneba API集成而编写的。传感器做两件事：a(通过REST API提交Spark作业，b(等待作业完成。

该操作符扩展了SimpleHttpOperator，同时实现了HttpSensor从而组合了这两种功能。

class LivyBatchOperator(SimpleHttpOperator):
"""
Submits a new Spark batch job through
the Apache Livy REST API.
"""
template_fields = ('args',)
ui_color = '#f4a460'
@apply_defaults
def __init__(self,
name,
className,
file,
executorMemory='1g',
driverMemory='512m',
driverCores=1,
executorCores=1,
numExecutors=1,
args=[],
conf={},
timeout=120,
http_conn_id='apache_livy',
*arguments, **kwargs):
"""
If xcom_push is True, response of an HTTP request will also
be pushed to an XCom.
"""
super(LivyBatchOperator, self).__init__(
endpoint='batches', *arguments, **kwargs)
self.http_conn_id = http_conn_id
self.method = 'POST'
self.endpoint = 'batches'
self.name = name
self.className = className
self.file = file
self.executorMemory = executorMemory
self.driverMemory = driverMemory
self.driverCores = driverCores
self.executorCores = executorCores
self.numExecutors = numExecutors
self.args = args
self.conf = conf
self.timeout = timeout
self.poke_interval = 10
def execute(self, context):
"""
Executes the task
"""
payload = {
"name": self.name,
"className": self.className,
"executorMemory": self.executorMemory,
"driverMemory": self.driverMemory,
"driverCores": self.driverCores,
"executorCores": self.executorCores,
"numExecutors": self.numExecutors,
"file": self.file,
"args": self.args,
"conf": self.conf
}
print payload
headers = {
'X-Requested-By': 'airflow',
'Content-Type': 'application/json'
}
http = HttpHook(self.method, http_conn_id=self.http_conn_id)
self.log.info("Submitting batch through Apache Livy API")
response = http.run(self.endpoint,
json.dumps(payload),
headers,
self.extra_options)
# parse the JSON response
obj = json.loads(response.content)
# get the new batch Id
self.batch_id = obj['id']
log.info('Batch successfully submitted with Id %s', self.batch_id)
# start polling the batch status
started_at = datetime.utcnow()
while not self.poke(context):
if (datetime.utcnow() - started_at).total_seconds() > self.timeout:
raise AirflowSensorTimeout('Snap. Time is OUT.')
sleep(self.poke_interval)
self.log.info("Batch %s has finished", self.batch_id)
def poke(self, context):
'''
Function that the sensors defined while deriving this class should
override.
'''
http = HttpHook(method='GET', http_conn_id=self.http_conn_id)
self.log.info("Calling Apache Livy API to get batch status")
# call the API endpoint
endpoint = 'batches/' + str(self.batch_id)
response = http.run(endpoint)
# parse the JSON response
obj = json.loads(response.content)
# get the current state of the batch
state = obj['state']
# check the batch state
if (state == 'starting') or (state == 'running'):
# if state is 'starting' or 'running'
# signal a new polling cycle
self.log.info('Batch %s has not finished yet (%s)',
self.batch_id, state)
return False
elif state == 'success':
# if state is 'success' exit
return True
else:
# for all other states
# raise an exception and
# terminate the task
raise AirflowException(
'Batch ' + str(self.batch_id) + ' failed (' + state + ')')

希望这能对你有所帮助。