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# Copyright (C) 2022 Microsoft Corporation.
#
# This file is part of cloud-init. See LICENSE file for license information.
import functools
from typing import Dict
import requests
from cloudinit import log as logging
from cloudinit import util
from cloudinit.sources.helpers.azure import report_diagnostic_event
from cloudinit.url_helper import UrlError, readurl, retry_on_url_exc
LOG = logging.getLogger(__name__)
IMDS_URL = "http://169.254.169.254/metadata"
_readurl_exception_callback = functools.partial(
retry_on_url_exc,
retry_codes=(
404, # not found (yet)
410, # gone / unavailable (yet)
429, # rate-limited/throttled
500, # server error
),
retry_instances=(
requests.ConnectionError,
requests.Timeout,
),
)
def _fetch_url(
url: str, *, log_response: bool = True, retries: int = 10, timeout: int = 2
) -> bytes:
"""Fetch URL from IMDS.
:raises UrlError: on error fetching metadata.
"""
try:
response = readurl(
url,
exception_cb=_readurl_exception_callback,
headers={"Metadata": "true"},
infinite=False,
log_req_resp=log_response,
retries=retries,
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,
) -> Dict:
"""Fetch IMDS metadata.
:raises UrlError: on error fetching metadata.
:raises ValueError: on error parsing metadata.
"""
metadata = _fetch_url(url)
try:
return util.load_json(metadata)
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() -> Dict:
"""Fetch extended metadata, falling back to non-extended as required.
:raises UrlError: on error fetching metadata.
:raises ValueError: on error parsing metadata.
"""
try:
url = IMDS_URL + "/instance?api-version=2021-08-01&extended=true"
return _fetch_metadata(url)
except UrlError as error:
if error.code == 400:
report_diagnostic_event(
"Falling back to IMDS api-version: 2019-06-01",
logger_func=LOG.warning,
)
url = IMDS_URL + "/instance?api-version=2019-06-01"
return _fetch_metadata(url)
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"
logging_threshold = 1
poll_counter = 0
def exception_callback(msg, exception):
nonlocal logging_threshold
nonlocal poll_counter
poll_counter += 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
retry = False
if exception.code in (404, 410):
retry = True
if poll_counter >= logging_threshold:
# Exponential back-off on logging.
logging_threshold *= 2
else:
log = False
if log:
report_diagnostic_event(
"Polling IMDS failed with exception: %r count: %d"
% (exception, poll_counter),
logger_func=LOG.info,
)
return retry
response = readurl(
url,
exception_cb=exception_callback,
headers={"Metadata": "true"},
infinite=True,
log_req_resp=False,
timeout=2,
)
report_diagnostic_event(
f"Polled IMDS {poll_counter+1} time(s)",
logger_func=LOG.debug,
)
return response.contents
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