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"""Reads and then deletes the message from SQS queue"""
import json
from typing import TYPE_CHECKING, Any, Optional, Sequence
from jsonpath_ng import parse
from typing_extensions import Literal
from airflow.exceptions import AirflowException
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 SQS queue and then deletes the message from the SQS queue.
If deletion of messages fails an AirflowException is thrown otherwise, the message
is pushed through XCom with the key ``messages``.
:param aws_conn_id: AWS connection id
:type aws_conn_id: str
:param sqs_queue: The SQS queue url (templated)
:type sqs_queue: str
:param max_messages: The maximum number of messages to retrieve for each poke (templated)
:type max_messages: int
:param wait_time_seconds: The time in seconds to wait for receiving messages (default: 1 second)
:type wait_time_seconds: int
:param visibility_timeout: Visibility timeout, a period of time during which
Amazon SQS prevents other consumers from receiving and processing the message.
:type visibility_timeout: Optional[Int]
: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.
:type message_filtering: Optional[Literal["literal", "jsonpath"]]
: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.
:type message_filtering_match_values: Any
: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.
:type message_filtering_config: Any
"""
[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,
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,
**kwargs,
):
super().__init__(**kwargs)
self.sqs_queue = sqs_queue
self.aws_conn_id = aws_conn_id
self.max_messages = max_messages
self.wait_time_seconds = wait_time_seconds
self.visibility_timeout = visibility_timeout
self.message_filtering = message_filtering
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 poke(self, context: 'Context'):
"""
Check for message on subscribed queue and write to xcom the message with key ``messages``
:param context: the context object
:type context: dict
:return: ``True`` if message is available or ``False``
"""
sqs_conn = self.get_hook().get_conn()
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 False
messages = response['Messages']
num_messages = len(messages)
self.log.info("Received %d messages", num_messages)
if not num_messages:
return False
if self.message_filtering:
messages = self.filter_messages(messages)
num_messages = len(messages)
self.log.info("There are %d messages left after filtering", num_messages)
if not num_messages:
return False
self.log.info("Deleting %d messages", num_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' in response:
context['ti'].xcom_push(key='messages', value=messages)
return True
else:
raise AirflowException(
'Delete SQS Messages failed ' + str(response) + ' for messages ' + str(messages)
)
[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