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This module contains a hook (AwsLogsHook) with some very basic
functionality for interacting with AWS CloudWatch.
from __future__ import annotations

from typing import Generator

from 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
[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:`` """ def __init__(self, *args, **kwargs) -> None: kwargs["client_type"] = "logs" super().__init__(*args, **kwargs)
[docs] def get_log_events( self, log_group: str, log_stream_name: str, start_time: int = 0, skip: int = 0, start_from_head: bool = True, ) -> Generator: """ A generator for log items in a single stream. This will yield all the items that are 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: whether to start from the beginning (True) of the log or at the end of the log (False). :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. """ num_consecutive_empty_response = 0 next_token = None while True: if next_token is not None: token_arg: dict[str, str] = {"nextToken": next_token} 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 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 elif next_token != response["nextForwardToken"]: num_consecutive_empty_response = 0 else: # Exit if the value of nextForwardToken is same in subsequent calls return next_token = response["nextForwardToken"]

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