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# Copyright (C) 2022 Microsoft Corporation.
#
# This file is part of cloud-init. See LICENSE file for license information.
import logging
from time import time
from typing import Dict, Optional, Type, Union
import requests
from cloudinit import util
from cloudinit.sources.helpers.azure import report_diagnostic_event
from cloudinit.url_helper import UrlError, readurl
LOG = logging.getLogger(__name__)
IMDS_URL = "http://169.254.169.254/metadata"
class ReadUrlRetryHandler:
"""Manager for readurl retry behavior using exception_callback().
:param logging_backoff: Backoff to limit logging.
:param max_connection_errors: Number of connection errors to retry on.
:param retry_codes: Set of http codes to retry on.
:param retry_deadline: Optional time()-based deadline to retry until.
"""
def __init__(
self,
*,
logging_backoff: float = 1.0,
max_connection_errors: Optional[int] = None,
retry_codes=(
404, # not found (yet)
410, # gone / unavailable (yet)
429, # rate-limited/throttled
500, # server error
),
retry_deadline: Optional[float] = None,
) -> None:
self.logging_backoff = logging_backoff
self.max_connection_errors = max_connection_errors
self.retry_codes = retry_codes
self.retry_deadline = retry_deadline
self._logging_threshold = 1.0
self._request_count = 0
self._last_error: Union[None, Type, int] = None
def exception_callback(self, req_args, exception) -> bool:
self._request_count += 1
if not isinstance(exception, UrlError):
report_diagnostic_event(
"Polling IMDS failed with unexpected exception: %r"
% (exception),
logger_func=LOG.warning,
)
return False
log = True
if self.retry_deadline is not None and time() >= self.retry_deadline:
retry = False
else:
retry = True
# Check for connection errors which may occur early boot, but
# are otherwise indicative that we are not connecting with the
# primary NIC.
if self.max_connection_errors is not None and isinstance(
exception.cause, requests.ConnectionError
):
self.max_connection_errors -= 1
if self.max_connection_errors <= 0:
retry = False
elif (
exception.code is not None
and exception.code not in self.retry_codes
):
retry = False
if self._request_count >= self._logging_threshold:
self._logging_threshold *= self.logging_backoff
else:
log = False
# Always log if error does not match previous.
if exception.code is not None:
# This is an HTTP response with failing code, log if different.
if self._last_error != exception.code:
log = True
self._last_error = exception.code
elif (
# No previous error to match against.
self._last_error is None
# Previous error is exception code (int).
or not isinstance(self._last_error, type)
# Previous error is different class.
or not isinstance(exception.cause, self._last_error)
):
log = True
self._last_error = type(exception.cause)
if log or not retry:
report_diagnostic_event(
"Polling IMDS failed attempt %d with exception: %r"
% (self._request_count, exception),
logger_func=LOG.warning,
)
return retry
def _fetch_url(
url: str,
*,
retry_handler: ReadUrlRetryHandler,
log_response: bool = True,
timeout: int = 30,
) -> bytes:
"""Fetch URL from IMDS.
:param url: url to fetch.
:param log_response: log responses in readurl().
:param retry_deadline: time()-based deadline to retry until.
:param timeout: Read/connection timeout in seconds for readurl().
:raises UrlError: on error fetching metadata.
"""
try:
response = readurl(
url,
exception_cb=retry_handler.exception_callback,
headers={"Metadata": "true"},
infinite=True,
log_req_resp=log_response,
timeout=timeout,
)
except UrlError as error:
report_diagnostic_event(
"Failed to fetch metadata from IMDS: %s" % error,
logger_func=LOG.warning,
)
raise
return response.contents
def _fetch_metadata(
url: str,
*,
retry_handler: ReadUrlRetryHandler,
) -> Dict:
"""Fetch IMDS metadata.
:param url: url to fetch.
:param retry_deadline: time()-based deadline to retry until.
:raises UrlError: on error fetching metadata.
:raises ValueError: on error parsing metadata.
"""
metadata = _fetch_url(url, retry_handler=retry_handler)
try:
return util.load_json(metadata.decode("utf-8"))
except ValueError as error:
report_diagnostic_event(
"Failed to parse metadata from IMDS: %s" % error,
logger_func=LOG.warning,
)
raise
def fetch_metadata_with_api_fallback(
retry_deadline: float, max_connection_errors: Optional[int] = None
) -> Dict:
"""Fetch extended metadata, falling back to non-extended as required.
:param retry_deadline: time()-based deadline to retry until.
:raises UrlError: on error fetching metadata.
:raises ValueError: on error parsing metadata.
"""
retry_handler = ReadUrlRetryHandler(
max_connection_errors=max_connection_errors,
retry_deadline=retry_deadline,
)
try:
url = IMDS_URL + "/instance?api-version=2021-08-01&extended=true"
return _fetch_metadata(url, retry_handler=retry_handler)
except UrlError as error:
if error.code == 400:
report_diagnostic_event(
"Falling back to IMDS api-version: 2019-06-01",
logger_func=LOG.warning,
)
retry_handler = ReadUrlRetryHandler(
max_connection_errors=max_connection_errors,
retry_deadline=retry_deadline,
)
url = IMDS_URL + "/instance?api-version=2019-06-01"
return _fetch_metadata(url, retry_handler=retry_handler)
raise
def fetch_reprovision_data() -> bytes:
"""Fetch extended metadata, falling back to non-extended as required.
:raises UrlError: on error.
"""
url = IMDS_URL + "/reprovisiondata?api-version=2019-06-01"
handler = ReadUrlRetryHandler(
logging_backoff=2.0,
max_connection_errors=1,
retry_codes=(
404,
410,
429,
),
retry_deadline=None,
)
response = readurl(
url,
exception_cb=handler.exception_callback,
headers={"Metadata": "true"},
infinite=True,
log_req_resp=False,
timeout=30,
)
report_diagnostic_event(
f"Polled IMDS {handler._request_count+1} time(s)",
logger_func=LOG.debug,
)
return response.contents
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