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# Copyright 2019 PrivateStorage.io, LLC
#
# 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.
from datetime import timedelta
from isodate import parse_duration
from .lease_maintenance import (
LeaseMaintenanceConfig,
)
class _EmptyConfig(object):
"""
Weakly pretend to be a Tahoe-LAFS configuration object with no
configuration.
"""
def get_config(self, section, option, default=object(), boolean=False):
return default
empty_config = _EmptyConfig()
def lease_maintenance_from_tahoe_config(node_config):
# type: (_Config) -> LeaseMaintenanceConfig
"""
Return a ``LeaseMaintenanceConfig`` representing the values from the given
configuration object.
"""
return LeaseMaintenanceConfig(
crawl_interval_mean=_read_duration(
node_config,
u"lease.crawl-interval.mean",
timedelta(days=26),
),
crawl_interval_range=_read_duration(
node_config,
u"lease.crawl-interval.range",
timedelta(days=4),
),
# The greater the min lease remaining time, the more of each lease
# period is "wasted" by renewing the lease before it has expired. The
# premise of ZKAPAuthorizer's use of leases is that if they expire,
# the storage server is free to reclaim the storage by forgetting
# about the share. However, since we do not know of any
# ZKAPAuthorizer-enabled storage grids which will garbage collect
# shares when leases expire, we have no reason not to use a zero
# duration here - for now.
#
# In the long run, storage servers must run with garbage collection
# enabled. Ideally, before that happens, we will have a system that
# doesn't involve trading of wasted lease time against reliability of
# leases being renewed before the shares are garbage collected.
#
# Also, since this is configuration, you can set it to something else
# if you want.
min_lease_remaining=_read_duration(
node_config,
u"lease.min-time-remaining",
timedelta(days=0),
),
)
def _read_duration(cfg, option, default):
"""
Read an ISO8601 "duration" from the ZKAPAuthorizer section of a Tahoe-LAFS
config.
:param cfg: The Tahoe-LAFS config object to consult.
:param option: The name of the option to read.
:return: ``None`` if the option is missing, otherwise the parsed duration
as a ``timedelta``.
"""
# type: (_Config, str) -> Optional[timedelta]
section_name = u"storageclient.plugins.privatestorageio-zkapauthz-v1"
value_str = cfg.get_config(
section=section_name,
option=option,
default=None,
)
if value_str is None:
return default
return parse_duration(value_str)