253 lines
8.4 KiB
Python
253 lines
8.4 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
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# Copyright (C) 2013 Rackspace Hosting All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import contextlib
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import copy
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import posixpath as pp
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from taskflow import exceptions as exc
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from taskflow.persistence import path_based
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from taskflow.types import tree
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from taskflow.utils import lock_utils
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class FakeFilesystem(object):
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"""An in-memory filesystem-like structure.
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This filesystem uses posix style paths **only** so users must be careful
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to use the ``posixpath`` module instead of the ``os.path`` one which will
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vary depending on the operating system which the active python is running
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in (the decision to use ``posixpath`` was to avoid the path variations
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which are not relevant in an implementation of a in-memory fake
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filesystem).
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Example usage:
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>>> from taskflow.persistence.backends import impl_memory
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>>> fs = impl_memory.FakeFilesystem()
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>>> fs.ensure_path('/a/b/c')
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>>> fs['/a/b/c'] = 'd'
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>>> print(fs['/a/b/c'])
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d
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>>> del fs['/a/b/c']
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>>> fs.ls("/a/b")
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[]
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"""
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#: Root path of the in-memory filesystem.
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root_path = pp.sep
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@classmethod
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def _normpath(cls, path):
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if not path.startswith(cls.root_path):
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raise ValueError("This filesystem can only normalize absolute"
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" paths: '%s' is not valid" % path)
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return pp.normpath(path)
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def __init__(self, deep_copy=True):
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self._root = tree.Node(self.root_path, value=None)
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if deep_copy:
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self._copier = copy.deepcopy
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else:
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self._copier = copy.copy
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def ensure_path(self, path):
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"""Ensure the path (and parents) exists."""
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path = self._normpath(path)
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# Ignore the root path as we already checked for that; and it
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# will always exist/can't be removed anyway...
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if path == self._root.item:
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return
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node = self._root
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for piece in self._iter_pieces(path):
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child_node = node.find(piece, only_direct=True,
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include_self=False)
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if child_node is None:
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child_node = tree.Node(piece, value=None)
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node.add(child_node)
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node = child_node
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def _fetch_node(self, path):
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node = self._root
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path = self._normpath(path)
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if path == self._root.item:
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return node
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for piece in self._iter_pieces(path):
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node = node.find(piece, only_direct=True,
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include_self=False)
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if node is None:
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raise exc.NotFound("Path '%s' not found" % path)
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return node
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def _get_item(self, path, links=None):
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node = self._fetch_node(path)
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if 'target' in node.metadata:
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# Follow the link (and watch out for loops)...
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path = node.metadata['target']
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if links is None:
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links = []
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if path in links:
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raise ValueError("Recursive link following not"
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" allowed (loop %s detected)"
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% (links + [path]))
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else:
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links.append(path)
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return self._get_item(path, links=links)
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else:
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return self._copier(node.metadata['value'])
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def ls(self, path):
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"""Return list of all children of the given path."""
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return [node.item for node in self._fetch_node(path)]
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def clear(self):
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for node in list(self._root.reverse_iter()):
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node.disassociate()
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def _iter_pieces(self, path, include_root=False):
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if path == self._root.item:
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# Check for this directly as the following doesn't work with
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# split correctly:
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#
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# >>> path = "/"
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# path.split(pp.sep)
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# ['', '']
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parts = []
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else:
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parts = path.split(pp.sep)[1:]
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if include_root:
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parts.insert(0, self._root.item)
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for piece in parts:
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yield piece
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def __delitem__(self, path):
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node = self._fetch_node(path)
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if node is self._root:
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raise ValueError("Can not delete '%s'" % self._root.item)
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node.disassociate()
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def pformat(self):
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"""Pretty format this in-memory filesystem."""
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return self._root.pformat()
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def symlink(self, src_path, dest_path):
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"""Link the destionation path to the source path."""
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dest_path = self._normpath(dest_path)
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src_path = self._normpath(src_path)
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dirname, basename = pp.split(dest_path)
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parent_node = self._fetch_node(dirname)
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child_node = parent_node.find(basename,
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only_direct=True,
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include_self=False)
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if child_node is None:
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child_node = tree.Node(basename, value=None)
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parent_node.add(child_node)
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child_node.metadata['target'] = src_path
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def __getitem__(self, path):
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return self._get_item(path)
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def __setitem__(self, path, value):
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path = self._normpath(path)
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value = self._copier(value)
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try:
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item_node = self._fetch_node(path)
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item_node.metadata.update(value=value)
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except exc.NotFound:
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dirname, basename = pp.split(path)
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parent_node = self._fetch_node(dirname)
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parent_node.add(tree.Node(basename, value=value))
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class MemoryBackend(path_based.PathBasedBackend):
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"""A in-memory (non-persistent) backend.
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This backend writes logbooks, flow details, and atom details to a
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in-memory filesystem-like structure (rooted by the ``memory``
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instance variable).
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This backend does *not* provide true transactional semantics. It does
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guarantee that there will be no inter-thread race conditions when
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writing and reading by using a read/write locks.
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"""
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def __init__(self, conf=None):
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super(MemoryBackend, self).__init__(conf)
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if self._path is None:
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self._path = pp.sep
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self.memory = FakeFilesystem(deep_copy=self._conf.get('deep_copy',
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True))
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self.lock = lock_utils.ReaderWriterLock()
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def get_connection(self):
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return Connection(self)
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def close(self):
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pass
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class Connection(path_based.PathBasedConnection):
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def __init__(self, backend):
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super(Connection, self).__init__(backend)
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self.upgrade()
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@contextlib.contextmanager
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def _memory_lock(self, write=False):
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if write:
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lock = self.backend.lock.write_lock
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else:
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lock = self.backend.lock.read_lock
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with lock():
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try:
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yield
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except exc.TaskFlowException as e:
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raise
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except Exception as e:
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raise exc.StorageFailure("Storage backend internal error", e)
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def _join_path(self, *parts):
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return pp.join(*parts)
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def _get_item(self, path):
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with self._memory_lock():
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return self.backend.memory[path]
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def _set_item(self, path, value, transaction):
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self.backend.memory[path] = value
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def _del_tree(self, path, transaction):
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del self.backend.memory[path]
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def _get_children(self, path):
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with self._memory_lock():
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return self.backend.memory.ls(path)
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def _ensure_path(self, path):
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with self._memory_lock(write=True):
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self.backend.memory.ensure_path(path)
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def _create_link(self, src_path, dest_path, transaction):
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self.backend.memory.symlink(src_path, dest_path)
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@contextlib.contextmanager
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def _transaction(self):
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"""This just wraps a global write-lock."""
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with self._memory_lock(write=True):
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yield
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def validate(self):
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pass
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