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✏️ Editing: cloud_config.py

# Copyright (C) 2012 Canonical Ltd.
# Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Juerg Haefliger <juerg.haefliger@hp.com>
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import logging

import jsonpatch

from cloudinit import handlers, mergers, safeyaml, util
from cloudinit.settings import PER_ALWAYS

LOG = logging.getLogger(__name__)

MERGE_HEADER = "Merge-Type"

# Due to the way the loading of yaml configuration was done previously,
# where previously each cloud config part was appended to a larger yaml
# file and then finally that file was loaded as one big yaml file we need
# to mimic that behavior by altering the default strategy to be replacing
# keys of prior merges.
#
#
# For example
# #file 1
# a: 3
# #file 2
# a: 22
# #combined file (comments not included)
# a: 3
# a: 22
#
# This gets loaded into yaml with final result {'a': 22}
DEF_MERGERS = mergers.string_extract_mergers("dict(replace)+list()+str()")
CLOUD_PREFIX = "#cloud-config"
JSONP_PREFIX = "#cloud-config-jsonp"

MERGED_PART_SCHEMA_ERROR_PREFIX = "# Cloud-config part ignored SCHEMA_ERROR: "

class CloudConfigPartHandler(handlers.Handler):

# The content prefixes this handler understands.
    prefixes = [CLOUD_PREFIX, JSONP_PREFIX]

def __init__(self, paths, **_kwargs):
        handlers.Handler.__init__(self, PER_ALWAYS, version=3)
        self.cloud_buf = None
        self.cloud_fn = paths.get_ipath("cloud_config")
        if "cloud_config_path" in _kwargs:
            self.cloud_fn = paths.get_ipath(_kwargs["cloud_config_path"])
        self.file_names = []
        self.error_file_names = []

def _write_cloud_config(self):
        if not self.cloud_fn:
            return
        # Capture which files we merged from...
        file_lines = []
        if self.file_names:
            file_lines.append("# from %s files" % (len(self.file_names)))
            for fn in self.file_names:
                if not fn:
                    fn = "?"
                file_lines.append("# %s" % (fn))
            file_lines.append("")
        for error_file in self.error_file_names:
            file_lines.append(f"{MERGED_PART_SCHEMA_ERROR_PREFIX}{error_file}")
        if self.cloud_buf is not None:
            # Something was actually gathered....
            lines = [
                CLOUD_PREFIX,
                "",
            ]
            lines.extend(file_lines)
            lines.append(safeyaml.dumps(self.cloud_buf))
        else:
            lines = []
        util.write_file(self.cloud_fn, "\n".join(lines), 0o600)

def _extract_mergers(self, payload, headers):
        merge_header_headers = ""
        for h in [MERGE_HEADER, "X-%s" % (MERGE_HEADER)]:
            tmp_h = headers.get(h, "")
            if tmp_h:
                merge_header_headers = tmp_h
                break
        # Select either the merge-type from the content
        # or the merge type from the headers or default to our own set
        # if neither exists (or is empty) from the later.
        payload_yaml = util.load_yaml(payload)
        if payload_yaml is None:
            raise ValueError("empty cloud config")

mergers_yaml = mergers.dict_extract_mergers(payload_yaml)
        mergers_header = mergers.string_extract_mergers(merge_header_headers)
        all_mergers = []
        all_mergers.extend(mergers_yaml)
        all_mergers.extend(mergers_header)
        if not all_mergers:
            all_mergers = DEF_MERGERS
        return (payload_yaml, all_mergers)

def _merge_patch(self, payload):
        # JSON doesn't handle comments in this manner, so ensure that
        # if we started with this 'type' that we remove it before
        # attempting to load it as json (which the jsonpatch library will
        # attempt to do).
        payload = payload.lstrip()
        payload = util.strip_prefix_suffix(payload, prefix=JSONP_PREFIX)
        patch = jsonpatch.JsonPatch.from_string(payload)
        LOG.debug("Merging by applying json patch %s", patch)
        self.cloud_buf = patch.apply(self.cloud_buf, in_place=False)

def _merge_part(self, payload, headers):
        (payload_yaml, my_mergers) = self._extract_mergers(payload, headers)
        LOG.debug("Merging by applying %s", my_mergers)
        merger = mergers.construct(my_mergers)
        self.cloud_buf = merger.merge(self.cloud_buf, payload_yaml)

def _reset(self):
        self.file_names = []
        self.cloud_buf = None

def handle_part(self, data, ctype, filename, payload, frequency, headers):
        if ctype == handlers.CONTENT_START:
            self._reset()
            return
        if ctype == handlers.CONTENT_END:
            self._write_cloud_config()
            self._reset()
            return
        try:
            # First time through, merge with an empty dict...
            if self.cloud_buf is None or not self.file_names:
                self.cloud_buf = {}
            if ctype == handlers.INCLUSION_TYPES_MAP[JSONP_PREFIX]:
                self._merge_patch(payload)
            else:
                self._merge_part(payload, headers)
            # Ensure filename is ok to store
            for i in ("\n", "\r", "\t"):
                filename = filename.replace(i, " ")
            self.file_names.append(filename.strip())
        except ValueError as err:
            self.error_file_names.append(filename.strip())
            LOG.warning(
                "Failed at merging in cloud config part from %s: %s",
                filename,
                err,
            )
        except Exception:
            util.logexc(
                LOG, "Failed at merging in cloud config part from %s", filename
            )

MR SKB