def _dispatch(self, alert, descriptor):
"""Send alert to an SNS topic
Args:
alert (Alert): Alert instance which triggered a rule
descriptor (str): Output descriptor
Returns:
bool: True if alert was sent successfully, False otherwise
"""
# SNS topics can only be accessed via their ARN
topic_name = self.config[self.__service__][descriptor]
topic_arn = 'arn:aws:sns:{}:{}:{}'.format(self.region, self.account_id,
topic_name)
topic = boto3.resource('sns', region_name=self.region).Topic(topic_arn)
publication = compose_alert(alert, self, descriptor)
# Presentation defaults
default_subject = '{} triggered alert {}'.format(
alert.rule_name, alert.alert_id)
default_message = json.dumps(publication, indent=2, sort_keys=True)
# Published presentation fields
# Subject must be < 100 characters long;
subject = elide_string_middle(
publication.get('@aws-sns.topic', default_subject), 99)
message = publication.get('@aws-sns.message', default_message)
topic.publish(Message=message, Subject=subject)
return True
def _standardize_custom_attachments(cls, custom_slack_attachments):
"""Supplies default fields to given attachments and validates their structure.
You can test out custom attachments using this tool:
https://api.slack.com/docs/messages/builder
When publishers provider custom slack attachments to the SlackOutput, it offers increased
flexibility, but requires more work. Publishers need to pay attention to the following:
- Slack requires escaping the characters: '&', '>' and '<'
- Slack messages have a limit of 4000 characters
- Individual slack messages support a maximum of 20 attachments
Args:
custom_slack_attachments (list): A list of dicts that is provided by the publisher.
Returns:
list: The value to the "attachments" Slack API argument
"""
attachments = []
for custom_slack_attachment in custom_slack_attachments:
attachment = cls._get_attachment_skeleton()
attachment.update(custom_slack_attachment)
# Enforce maximum text length; make sure to check size AFTER escaping in case
# extra escape characters pushes it over the limit
if len(attachment['text']) > cls.MAX_MESSAGE_SIZE:
LOGGER.warning(
'Custom attachment was truncated to length %d. Full message: %s',
cls.MAX_MESSAGE_SIZE, attachment['text'])
attachment['text'] = elide_string_middle(
attachment['text'], cls.MAX_MESSAGE_SIZE)
attachments.append(attachment)
# Enforce maximum number of attachments
if len(attachments) >= cls.MAX_ATTACHMENTS:
LOGGER.warning(
'Message with %d custom attachments was truncated to %d attachments',
len(custom_slack_attachments), cls.MAX_ATTACHMENTS)
break
return attachments
def test_elide_string_middle():
"""Alert Processor - Helpers - String Truncation"""
alphabet = 'abcdefghijklmnopqrstuvwxyz'
# String shortened
assert_equal('ab ... yz', elide_string_middle(alphabet, 10))
assert_equal('abcde ... vwxyz', elide_string_middle(alphabet, 15))
assert_equal('abcdefg ... tuvwxyz', elide_string_middle(alphabet, 20))
assert_equal('abcdefghij ... qrstuvwxyz',
elide_string_middle(alphabet, 25))
# String unchanged
assert_equal(alphabet, elide_string_middle(alphabet, 26))
assert_equal(alphabet, elide_string_middle(alphabet, 50))