自動デプロイとアプリケーションの設定値と etcd

# -*- coding: utf-8 -*-

"""
Copyright (c) 2015, Kohei YOSHIDA <[email protected]>. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the copyright holder nor the names of its
      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""

import json
from urlparse import urlparse

import etcd


class ConfigRegistry(object):

    def __init__(self, parent, name):
        self.parent = parent
        self.name = name

    @property
    def root(self):
        if isinstance(self.parent, Config):
            return self.parent

        return self.parent.root

    @property
    def keyname(self):
        if isinstance(self.parent, Config):
            return '/'.join((self.parent.key_prefix, self.name))

        return '/'.join((self.parent.keyname, self.name))

    def read(self):
        return json.loads(self.root.client.read(self.keyname).value)

    def write(self, value):
        return self.root.client.write(self.keyname, json.dumps(value))

    def __getattr__(self, name):
        return ConfigRegistry(self, name)


class Config(object):

    def __init__(self, url, client_cert, client_key):
        self.url = url if url.endswith('/') else url + '/'
        self.__etcd_registry__ = {}

        parsed = urlparse(url)
        path_parts = parsed.path.split('/', 3)
        if len(path_parts) != 4\
                or path_parts[2] != 'keys':  # /v2/keys/appname/staging
            raise ValueError()

        self.key_prefix = '/' + path_parts[3]
        self.client = etcd.Client(host=parsed.hostname,
                                  port=parsed.port,
                                  protocol=parsed.scheme,
                                  cert=(client_cert, client_key))

    def __getattr__(self, name):
        if name not in self.__etcd_registry__:
            self.__etcd_registry__[name] = ConfigRegistry(self, name)

        return self.__etcd_registry__[name]

config = PasteConfig('https://etcd.example.com:4001/v2/keys/appname/staging',
                     './etcd.cer',
                     './etcd.key')
config.foo.bar.read()  # https://etcd.example.com:4001/v2/keys/appname/staging/foo/bar