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from __future__ import annotations

import warnings
from typing import Generator

from airflow.exceptions import AirflowProviderDeprecationWarning
from import AwsBaseHook
from airflow.utils.helpers import prune_dict

# 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] 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, end_time: int | None = None, ) -> Generator: """ Return 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 timestamp value in ms 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. :param end_time: The timestamp value in ms to stop reading the logs from (default: None). If None is provided, reads it until the end of the log stream :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( **prune_dict( { "logGroupName": log_group, "logStreamName": log_stream_name, "startTime": start_time, "endTime": end_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"]

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