tooz.drivers.etcd3

Source code for tooz.drivers.etcd3

# -*- coding: utf-8 -*-
#
# 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 __future__ import absolute_import
import contextlib
import functools
import threading

import etcd3
from etcd3 import exceptions as etcd3_exc
from oslo_utils import encodeutils
import six

import tooz
from tooz import _retry
from tooz import coordination
from tooz import locking
from tooz import utils


@contextlib.contextmanager
def _failure_translator():
    """Translates common requests exceptions into tooz exceptions."""
    try:
        yield
    except etcd3_exc.ConnectionFailedError as e:
        utils.raise_with_cause(coordination.ToozConnectionError,
                               encodeutils.exception_to_unicode(e),
                               cause=e)
    except etcd3_exc.ConnectionTimeoutError as e:
        utils.raise_with_cause(coordination.OperationTimedOut,
                               encodeutils.exception_to_unicode(e),
                               cause=e)
    except etcd3_exc.Etcd3Exception as e:
        utils.raise_with_cause(coordination.ToozError,
                               encodeutils.exception_to_unicode(e),
                               cause=e)


def _translate_failures(func):

    @six.wraps(func)
    def wrapper(*args, **kwargs):
        with _failure_translator():
            return func(*args, **kwargs)

    return wrapper


class Etcd3Lock(locking.Lock):
    """An etcd3-specific lock.

    Thin wrapper over etcd3's lock object basically to provide the heartbeat()
    semantics for the coordination driver.
    """

    LOCK_PREFIX = b"/tooz/locks"

    def __init__(self, coord, name, timeout):
        super(Etcd3Lock, self).__init__(name)
        self._coord = coord
        self._lock = coord.client.lock(name.decode(), timeout)
        self._exclusive_access = threading.Lock()

    @_translate_failures
    def acquire(self, blocking=True, shared=False):
        if shared:
            raise tooz.NotImplemented

        blocking, timeout = utils.convert_blocking(blocking)
        if blocking is False:
            timeout = 0

        if self._lock.acquire(timeout):
            self._coord._acquired_locks.add(self)
            return True

        return False

    @property
    def acquired(self):
        return self in self._coord._acquired_locks

    @_translate_failures
    def release(self):
        with self._exclusive_access:
            if self.acquired and self._lock.release():
                self._coord._acquired_locks.discard(self)
                return True
        return False

    @_translate_failures
    def heartbeat(self):
        with self._exclusive_access:
            if self.acquired:
                self._lock.refresh()
                return True
        return False


[docs]class Etcd3Driver(coordination.CoordinationDriverCachedRunWatchers, coordination.CoordinationDriverWithExecutor): """An etcd based driver. This driver uses etcd provide the coordination driver semantics and required API(s). The Etcd driver connection URI should look like:: etcd3://[HOST[:PORT]][?OPTION1=VALUE1[&OPTION2=VALUE2[&...]]] If not specified, HOST defaults to localhost and PORT defaults to 2379. Available options are: ================== ======= Name Default ================== ======= protocol http timeout 30 lock_timeout 30 membership_timeout 30 ================== ======= """ #: Default socket/lock/member/leader timeout used when none is provided. DEFAULT_TIMEOUT = 30 #: Default hostname used when none is provided. DEFAULT_HOST = "localhost" #: Default port used if none provided (4001 or 2379 are the common ones). DEFAULT_PORT = 2379
[docs] def __init__(self, member_id, parsed_url, options): super(Etcd3Driver, self).__init__(member_id, parsed_url, options) host = parsed_url.hostname or self.DEFAULT_HOST port = parsed_url.port or self.DEFAULT_PORT options = utils.collapse(options) timeout = int(options.get('timeout', self.DEFAULT_TIMEOUT)) self.client = etcd3.client(host=host, port=port, timeout=timeout) self.lock_timeout = int(options.get('lock_timeout', timeout)) self.membership_timeout = int(options.get( 'membership_timeout', timeout)) self._acquired_locks = set()
def _start(self): super(Etcd3Driver, self)._start() self._membership_lease = self.client.lease(self.membership_timeout) def _stop(self): super(Etcd3Driver, self)._stop() self._membership_lease.revoke()
[docs] def get_lock(self, name): return Etcd3Lock(self, name, self.lock_timeout)
[docs] def heartbeat(self): # NOTE(jaypipes): Copying because set can mutate during iteration for lock in self._acquired_locks.copy(): lock.heartbeat() # TODO(jd) use the same lease for locks? self._membership_lease.refresh() return min(self.lock_timeout, self.membership_timeout)
GROUP_PREFIX = b"tooz/groups/" def _encode_group_id(self, group_id): return self.GROUP_PREFIX + utils.to_binary(group_id) + b"/" def _encode_group_member_id(self, group_id, member_id): return self._encode_group_id(group_id) + utils.to_binary(member_id)
[docs] def create_group(self, group_id): encoded_group = self._encode_group_id(group_id) @_translate_failures def _create_group(): status, results = self.client.transaction( compare=[ self.client.transactions.version( encoded_group) == 0 ], success=[ self.client.transactions.put(encoded_group, b"") ], failure=[], ) if not status: raise coordination.GroupAlreadyExist(group_id) return EtcdFutureResult(self._executor.submit(_create_group))
def _destroy_group(self, group_id): self.client.delete(self._encode_group_id(group_id))
[docs] def delete_group(self, group_id): encoded_group = self._encode_group_id(group_id) @_translate_failures def _delete_group(): members = list(self.client.get_prefix(encoded_group)) if len(members) > 1: raise coordination.GroupNotEmpty(group_id) # Warning: as of this writing python-etcd3 does not support the # NOT_EQUAL operator so we use the EQUAL operator and will retry on # success, hihi status, results = self.client.transaction( compare=[ self.client.transactions.version(encoded_group) == 0 ], success=[], failure=[ self.client.transactions.delete(encoded_group) ], ) if status: raise coordination.GroupNotCreated(group_id) return EtcdFutureResult(self._executor.submit(_delete_group))
[docs] def join_group(self, group_id, capabilities=b""): encoded_group = self._encode_group_id(group_id) @_retry.retry() @_translate_failures def _join_group(): members = list(self.client.get_prefix(encoded_group)) encoded_member = self._encode_group_member_id( group_id, self._member_id) group_metadata = None for cap, metadata in members: if metadata.key == encoded_member: raise coordination.MemberAlreadyExist(group_id, self._member_id) if metadata.key == encoded_group: group_metadata = metadata if group_metadata is None: raise coordination.GroupNotCreated(group_id) status, results = self.client.transaction( # This comparison makes sure the group has not been deleted in # the mean time compare=[ self.client.transactions.version(encoded_group) == group_metadata.version ], success=[ self.client.transactions.put(encoded_member, utils.dumps(capabilities), lease=self._membership_lease) ], failure=[], ) if not status: # TODO(jd) There's a small optimization doable by getting the # current range on failure and passing it to this function as # the first arg when retrying to avoid redoing a get_prefix() raise _retry.TryAgain return EtcdFutureResult(self._executor.submit(_join_group))
[docs] def leave_group(self, group_id): encoded_group = self._encode_group_id(group_id) @_translate_failures def _leave_group(): members = list(self.client.get_prefix(encoded_group)) encoded_member = self._encode_group_member_id( group_id, self._member_id) for capabilities, metadata in members: if metadata.key == encoded_member: break else: raise coordination.MemberNotJoined(group_id, self._member_id) self.client.delete(encoded_member) return EtcdFutureResult(self._executor.submit(_leave_group))
[docs] def get_members(self, group_id): encoded_group = self._encode_group_id(group_id) @_translate_failures def _get_members(): members = set() group_found = False for cap, metadata in self.client.get_prefix(encoded_group): if metadata.key == encoded_group: group_found = True else: members.add(metadata.key[len(encoded_group):]) if not group_found: raise coordination.GroupNotCreated(group_id) return members return EtcdFutureResult(self._executor.submit(_get_members))
[docs] def get_member_capabilities(self, group_id, member_id): encoded_member = self._encode_group_member_id( group_id, member_id) @_translate_failures def _get_member_capabilities(): capabilities, metadata = self.client.get(encoded_member) if capabilities is None: raise coordination.MemberNotJoined(group_id, member_id) return utils.loads(capabilities) return EtcdFutureResult( self._executor.submit(_get_member_capabilities))
[docs] def update_capabilities(self, group_id, capabilities): encoded_member = self._encode_group_member_id( group_id, self._member_id) @_translate_failures def _update_capabilities(): cap, metadata = self.client.get(encoded_member) if cap is None: raise coordination.MemberNotJoined(group_id, self._member_id) self.client.put(encoded_member, utils.dumps(capabilities), lease=self._membership_lease) return EtcdFutureResult( self._executor.submit(_update_capabilities))
[docs] @staticmethod def watch_elected_as_leader(group_id, callback): raise tooz.NotImplemented
[docs] @staticmethod def unwatch_elected_as_leader(group_id, callback): raise tooz.NotImplemented
EtcdFutureResult = functools.partial(coordination.CoordinatorResult, failure_translator=_failure_translator)
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