Source code for airflow.providers.amazon.aws.hooks.logs
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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
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# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
from __future__ import annotations
import warnings
from typing import Generator
from airflow.exceptions import AirflowProviderDeprecationWarning
from airflow.providers.amazon.aws.hooks.base_aws import AwsBaseHook
# Guidance received from the AWS team regarding the correct way to check for the end of a stream is that the
# value of the nextForwardToken is the same in subsequent calls.
# The issue with this approach is, it can take a huge amount of time (e.g. 20 seconds) to retrieve logs using
# this approach. As an intermediate solution, we decided to stop fetching logs if 3 consecutive responses
# are empty.
# See PR https://github.com/apache/airflow/pull/20814
[docs]NUM_CONSECUTIVE_EMPTY_RESPONSE_EXIT_THRESHOLD = 3
[docs]class AwsLogsHook(AwsBaseHook):
"""
Interact with Amazon CloudWatch Logs.
Provide thin wrapper around :external+boto3:py:class:`boto3.client("logs") <CloudWatchLogs.Client>`.
Additional arguments (such as ``aws_conn_id``) may be specified and
are passed down to the underlying AwsBaseHook.
.. seealso::
- :class:`airflow.providers.amazon.aws.hooks.base_aws.AwsBaseHook`
"""
def __init__(self, *args, **kwargs) -> None:
kwargs["client_type"] = "logs"
super().__init__(*args, **kwargs)
[docs] class ContinuationToken:
"""Just a wrapper around a str token to allow updating it from the caller."""
def __init__(self):
self.value: str | None = None
[docs] def get_log_events(
self,
log_group: str,
log_stream_name: str,
start_time: int = 0,
skip: int = 0,
start_from_head: bool | None = None,
continuation_token: ContinuationToken | None = None,
) -> Generator:
"""
A generator for log items in a single stream; yields all items available at the current moment.
.. seealso::
- :external+boto3:py:meth:`CloudWatchLogs.Client.get_log_events`
:param log_group: The name of the log group.
:param log_stream_name: The name of the specific stream.
:param start_time: The time stamp value to start reading the logs from (default: 0).
:param skip: The number of log entries to skip at the start (default: 0).
This is for when there are multiple entries at the same timestamp.
:param start_from_head: Deprecated. Do not use with False, logs would be retrieved out of order.
If possible, retrieve logs in one query, or implement pagination yourself.
:param continuation_token: a token indicating where to read logs from.
Will be updated as this method reads new logs, to be reused in subsequent calls.
:return: | A CloudWatch log event with the following key-value pairs:
| 'timestamp' (int): The time in milliseconds of the event.
| 'message' (str): The log event data.
| 'ingestionTime' (int): The time in milliseconds the event was ingested.
"""
if start_from_head is not None:
message = (
"start_from_head is deprecated, please remove this parameter."
if start_from_head
else "Do not use this method with start_from_head=False, logs will be returned out of order. "
"If possible, retrieve logs in one query, or implement pagination yourself."
)
warnings.warn(
message,
AirflowProviderDeprecationWarning,
stacklevel=2,
)
else:
start_from_head = True
if continuation_token is None:
continuation_token = AwsLogsHook.ContinuationToken()
num_consecutive_empty_response = 0
while True:
if continuation_token.value is not None:
token_arg: dict[str, str] = {"nextToken": continuation_token.value}
else:
token_arg = {}
response = self.conn.get_log_events(
logGroupName=log_group,
logStreamName=log_stream_name,
startTime=start_time,
startFromHead=start_from_head,
**token_arg,
)
events = response["events"]
event_count = len(events)
if event_count > skip:
events = events[skip:]
skip = 0
else:
skip -= event_count
events = []
yield from events
if continuation_token.value == response["nextForwardToken"]:
return
if not event_count:
num_consecutive_empty_response += 1
if num_consecutive_empty_response >= NUM_CONSECUTIVE_EMPTY_RESPONSE_EXIT_THRESHOLD:
# Exit if there are more than NUM_CONSECUTIVE_EMPTY_RESPONSE_EXIT_THRESHOLD consecutive
# empty responses
return
else:
num_consecutive_empty_response = 0
continuation_token.value = response["nextForwardToken"]
