Michael Davies 44e6949b0c Cache negotiated api microversion for server
If we negotiate an API microversion in the ironiccclient, cache
this value so that we don't need to re-negotiate it again for the
next API call, if the user doesn't specify a version.

We cache the version for a particular ironic instance in a
temporary file, one per server, in a multi-user, multi-server
safe-way - deleting old files once they expire, so only the
latest is kept.

Depends-On: Icb29fdc92ecd54e388b7c16899070572458308da
Change-Id: I0232bc611789fb96491d855020042e23ba0c4fab
Blueprint: version-caching
2015-06-23 08:55:12 +09:30

87 lines
2.5 KiB
Python

#
# Copyright 2015 Rackspace, Inc
# All Rights Reserved
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import os
import appdirs
import dogpile.cache
AUTHOR = 'openstack'
PROGNAME = 'python-ironicclient'
CACHE_DIR = appdirs.user_cache_dir(PROGNAME, AUTHOR)
CACHE_FILENAME = os.path.join(CACHE_DIR, 'ironic-api-version.dbm')
CACHE = None
DEFAULT_EXPIRY = 300 # seconds
def _get_cache():
"""Configure file caching."""
global CACHE
if CACHE is None:
# Ensure cache directory present
if not os.path.exists(CACHE_DIR):
os.makedirs(CACHE_DIR)
CACHE = dogpile.cache.make_region().configure(
'dogpile.cache.dbm',
expiration_time=DEFAULT_EXPIRY,
arguments={
"filename": CACHE_FILENAME,
}
)
return CACHE
def _build_key(host, port):
"""Build a key based upon the hostname or address supplied."""
return "%s:%s" % (host, port)
def save_data(host, port, data):
"""Save 'data' for a particular 'host' in the appropriate cache dir.
param host: The host that we need to save data for
param port: The port on the host that we need to save data for
param data: The data we want saved
"""
key = _build_key(host, port)
_get_cache().set(key, data)
def retrieve_data(host, port, expiry=None):
"""Retrieve the version stored for an ironic 'host', if it's not stale.
Check to see if there is valid cached data for the host/port
combination and return that if it isn't stale.
param host: The host that we need to retrieve data for
param port: The port on the host that we need to retrieve data for
param expiry: The age in seconds before cached data is deemed invalid
"""
# Ensure that a cache file exists first
if not os.path.isfile(CACHE_FILENAME):
return None
key = _build_key(host, port)
data = _get_cache().get(key, expiration_time=expiry)
if data == dogpile.cache.api.NO_VALUE:
return None
return data