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"""Reads and then deletes the message from SQS queue"""
import json
from typing import TYPE_CHECKING, Any, Collection, List, Optional, Sequence
from jsonpath_ng import parse
from typing_extensions import Literal
from airflow.exceptions import AirflowException
from airflow.providers.amazon.aws.hooks.base_aws import BaseAwsConnection
from airflow.providers.amazon.aws.hooks.sqs import SqsHook
from airflow.sensors.base import BaseSensorOperator
if TYPE_CHECKING:
from airflow.utils.context import Context
[docs]class SqsSensor(BaseSensorOperator):
"""
Get messages from an Amazon SQS queue and then delete the messages from the queue.
If deletion of messages fails, an AirflowException is thrown. Otherwise, the messages
are pushed through XCom with the key ``messages``.
By default,the sensor performs one and only one SQS call per poke, which limits the result to
a maximum of 10 messages. However, the total number of SQS API calls per poke can be controlled
by num_batches param.
.. seealso::
For more information on how to use this sensor, take a look at the guide:
:ref:`howto/sensor:SqsSensor`
:param aws_conn_id: AWS connection id
:param sqs_queue: The SQS queue url (templated)
:param max_messages: The maximum number of messages to retrieve for each poke (templated)
:param num_batches: The number of times the sensor will call the SQS API to receive messages (default: 1)
:param wait_time_seconds: The time in seconds to wait for receiving messages (default: 1 second)
:param visibility_timeout: Visibility timeout, a period of time during which
Amazon SQS prevents other consumers from receiving and processing the message.
:param message_filtering: Specified how received messages should be filtered. Supported options are:
`None` (no filtering, default), `'literal'` (message Body literal match) or `'jsonpath'`
(message Body filtered using a JSONPath expression).
You may add further methods by overriding the relevant class methods.
:param message_filtering_match_values: Optional value/s for the message filter to match on.
For example, with literal matching, if a message body matches any of the specified values
then it is included. For JSONPath matching, the result of the JSONPath expression is used
and may match any of the specified values.
:param message_filtering_config: Additional configuration to pass to the message filter.
For example with JSONPath filtering you can pass a JSONPath expression string here,
such as `'foo[*].baz'`. Messages with a Body which does not match are ignored.
:param delete_message_on_reception: Default to `True`, the messages are deleted from the queue
as soon as being consumed. Otherwise, the messages remain in the queue after consumption and
should be deleted manually.
"""
[docs] template_fields: Sequence[str] = ('sqs_queue', 'max_messages', 'message_filtering_config')
def __init__(
self,
*,
sqs_queue,
aws_conn_id: str = 'aws_default',
max_messages: int = 5,
num_batches: int = 1,
wait_time_seconds: int = 1,
visibility_timeout: Optional[int] = None,
message_filtering: Optional[Literal["literal", "jsonpath"]] = None,
message_filtering_match_values: Any = None,
message_filtering_config: Any = None,
delete_message_on_reception: bool = True,
**kwargs,
):
super().__init__(**kwargs)
self.sqs_queue = sqs_queue
self.aws_conn_id = aws_conn_id
self.max_messages = max_messages
self.num_batches = num_batches
self.wait_time_seconds = wait_time_seconds
self.visibility_timeout = visibility_timeout
self.message_filtering = message_filtering
self.delete_message_on_reception = delete_message_on_reception
if message_filtering_match_values is not None:
if not isinstance(message_filtering_match_values, set):
message_filtering_match_values = set(message_filtering_match_values)
self.message_filtering_match_values = message_filtering_match_values
if self.message_filtering == 'literal':
if self.message_filtering_match_values is None:
raise TypeError('message_filtering_match_values must be specified for literal matching')
self.message_filtering_config = message_filtering_config
self.hook: Optional[SqsHook] = None
[docs] def poll_sqs(self, sqs_conn: BaseAwsConnection) -> Collection:
"""
Poll SQS queue to retrieve messages.
:param sqs_conn: SQS connection
:return: A list of messages retrieved from SQS
"""
self.log.info('SqsSensor checking for message on queue: %s', self.sqs_queue)
receive_message_kwargs = {
'QueueUrl': self.sqs_queue,
'MaxNumberOfMessages': self.max_messages,
'WaitTimeSeconds': self.wait_time_seconds,
}
if self.visibility_timeout is not None:
receive_message_kwargs['VisibilityTimeout'] = self.visibility_timeout
response = sqs_conn.receive_message(**receive_message_kwargs)
if "Messages" not in response:
return []
messages = response['Messages']
num_messages = len(messages)
self.log.info("Received %d messages", num_messages)
if num_messages and self.message_filtering:
messages = self.filter_messages(messages)
num_messages = len(messages)
self.log.info("There are %d messages left after filtering", num_messages)
return messages
[docs] def poke(self, context: 'Context'):
"""
Check subscribed queue for messages and write them to xcom with the ``messages`` key.
:param context: the context object
:return: ``True`` if message is available or ``False``
"""
sqs_conn = self.get_hook().get_conn()
message_batch: List[Any] = []
# perform multiple SQS call to retrieve messages in series
for _ in range(self.num_batches):
messages = self.poll_sqs(sqs_conn=sqs_conn)
if not len(messages):
continue
message_batch.extend(messages)
if self.delete_message_on_reception:
self.log.info("Deleting %d messages", len(messages))
entries = [
{'Id': message['MessageId'], 'ReceiptHandle': message['ReceiptHandle']}
for message in messages
]
response = sqs_conn.delete_message_batch(QueueUrl=self.sqs_queue, Entries=entries)
if 'Successful' not in response:
raise AirflowException(
'Delete SQS Messages failed ' + str(response) + ' for messages ' + str(messages)
)
if not len(message_batch):
return False
context['ti'].xcom_push(key='messages', value=message_batch)
return True
[docs] def get_hook(self) -> SqsHook:
"""Create and return an SqsHook"""
if self.hook:
return self.hook
self.hook = SqsHook(aws_conn_id=self.aws_conn_id)
return self.hook
[docs] def filter_messages(self, messages):
if self.message_filtering == 'literal':
return self.filter_messages_literal(messages)
if self.message_filtering == 'jsonpath':
return self.filter_messages_jsonpath(messages)
else:
raise NotImplementedError('Override this method to define custom filters')
[docs] def filter_messages_literal(self, messages):
filtered_messages = []
for message in messages:
if message['Body'] in self.message_filtering_match_values:
filtered_messages.append(message)
return filtered_messages
[docs] def filter_messages_jsonpath(self, messages):
jsonpath_expr = parse(self.message_filtering_config)
filtered_messages = []
for message in messages:
body = message['Body']
# Body is a string, deserialize to an object and then parse
body = json.loads(body)
results = jsonpath_expr.find(body)
if not results:
continue
if self.message_filtering_match_values is None:
filtered_messages.append(message)
continue
for result in results:
if result.value in self.message_filtering_match_values:
filtered_messages.append(message)
break
return filtered_messages
