root / lib / vcluster.py @ 63a3d8f7
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# Copyright (C) 2012 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module containing utilities for virtual clusters.
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Most functions manipulate file system paths and are no-ops when the environment
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variables C{GANETI_ROOTDIR} and C{GANETI_HOSTNAME} are not set. See the
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functions' docstrings for details.
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"""
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import os |
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from ganeti import compat |
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_VIRT_PATH_PREFIX = "/###-VIRTUAL-PATH-###,"
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_ROOTDIR_ENVNAME = "GANETI_ROOTDIR"
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_HOSTNAME_ENVNAME = "GANETI_HOSTNAME"
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def _GetRootDirectory(envname): |
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"""Retrieves root directory from an environment variable.
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@type envname: string
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@param envname: Environment variable name
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@rtype: string
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@return: Root directory (can be empty)
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"""
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path = os.getenv(envname) |
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if path:
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if not os.path.isabs(path): |
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raise RuntimeError("Root directory in '%s' must be absolute: %s" % |
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(envname, path)) |
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return os.path.normpath(path)
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return "" |
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def _GetHostname(envname): |
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"""Retrieves virtual hostname from an environment variable.
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@type envname: string
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@param envname: Environment variable name
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@rtype: string
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@return: Host name (can be empty)
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"""
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return os.getenv(envname, default="") |
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def _CheckHostname(hostname): |
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"""Very basic check for hostnames.
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@type hostname: string
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@param hostname: Hostname
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"""
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if os.path.basename(hostname) != hostname:
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raise RuntimeError("Hostname '%s' can not be used for a file system" |
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" path" % hostname)
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def _PreparePaths(rootdir, hostname): |
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"""Checks if the root directory and hostname are acceptable.
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The (node-specific) root directory must have the hostname as its last
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component. The parent directory then becomes the cluster-wide root directory.
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This is necessary as some components must be able to predict the root path on
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a remote node (e.g. copying files via scp).
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@type rootdir: string
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@param rootdir: Root directory (from environment)
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@type hostname: string
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@param hostname: Hostname (from environment)
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@rtype: tuple; (string, string, string or None)
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@return: Tuple containing cluster-global root directory, node root directory
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and virtual hostname
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"""
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if bool(rootdir) ^ bool(hostname): |
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raise RuntimeError("Both root directory and hostname must be specified" |
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" using the environment variables %s and %s" %
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(_ROOTDIR_ENVNAME, _HOSTNAME_ENVNAME)) |
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if rootdir:
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assert rootdir == os.path.normpath(rootdir)
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_CheckHostname(hostname) |
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if os.path.basename(rootdir) != hostname:
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raise RuntimeError("Last component of root directory ('%s') must match" |
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" hostname ('%s')" % (rootdir, hostname))
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return (os.path.dirname(rootdir), rootdir, hostname)
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else:
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return ("", "", None) |
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(_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME) = \ |
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_PreparePaths(_GetRootDirectory(_ROOTDIR_ENVNAME), |
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_GetHostname(_HOSTNAME_ENVNAME)) |
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assert (compat.all([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]) or |
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not compat.any([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]))
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def GetVirtualHostname(): |
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"""Returns the virtual hostname.
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@rtype: string or L{None}
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"""
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return _VIRT_HOSTNAME
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def _MakeNodeRoot(base, node_name): |
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"""Appends a node name to the base directory.
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"""
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_CheckHostname(node_name) |
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return os.path.normpath("%s/%s" % (base, node_name)) |
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def ExchangeNodeRoot(node_name, filename, |
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_basedir=_VIRT_BASEDIR, _noderoot=_VIRT_NODEROOT): |
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"""Replaces the node-specific root directory in a path.
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Replaces it with the root directory for another node. Assuming
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C{/tmp/vcluster/node1} is the root directory for C{node1}, the result will be
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C{/tmp/vcluster/node3} for C{node3} (as long as a root directory is specified
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in the environment).
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"""
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if _basedir:
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pure = _RemoveNodePrefix(filename, _noderoot=_noderoot) |
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result = "%s/%s" % (_MakeNodeRoot(_basedir, node_name), pure)
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else:
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result = filename |
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return os.path.normpath(result)
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def EnvironmentForHost(hostname, _basedir=_VIRT_BASEDIR): |
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"""Returns the environment variables for a host.
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"""
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if _basedir:
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return {
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_ROOTDIR_ENVNAME: _MakeNodeRoot(_basedir, hostname), |
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_HOSTNAME_ENVNAME: hostname, |
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} |
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else:
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return {}
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def AddNodePrefix(path, _noderoot=_VIRT_NODEROOT): |
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"""Adds a node-specific prefix to a path in a virtual cluster.
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Returned path includes user-specified root directory if specified in
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environment. As an example, the path C{/var/lib/ganeti} becomes
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C{/tmp/vcluster/node1/var/lib/ganeti} if C{/tmp/vcluster/node1} is the root
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directory specified in the environment.
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"""
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assert os.path.isabs(path)
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if _noderoot:
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result = "%s/%s" % (_noderoot, path)
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else:
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result = path |
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assert os.path.isabs(result)
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return os.path.normpath(result)
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def _RemoveNodePrefix(path, _noderoot=_VIRT_NODEROOT): |
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"""Removes the node-specific prefix from a path.
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This is the opposite of L{AddNodePrefix} and removes a node-local prefix
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path.
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"""
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assert os.path.isabs(path)
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norm_path = os.path.normpath(path) |
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if _noderoot:
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# Make sure path is actually below node root
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norm_root = os.path.normpath(_noderoot) |
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root_with_sep = "%s%s" % (norm_root, os.sep)
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prefix = os.path.commonprefix([root_with_sep, norm_path]) |
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if prefix == root_with_sep:
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result = norm_path[len(norm_root):]
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else:
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raise RuntimeError("Path '%s' is not below node root '%s'" % |
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(path, _noderoot)) |
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else:
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result = norm_path |
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assert os.path.isabs(result)
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return result
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def MakeVirtualPath(path, _noderoot=_VIRT_NODEROOT): |
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"""Virtualizes a path.
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A path is "virtualized" by stripping it of its node-specific directory and
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prepending a prefix (L{_VIRT_PATH_PREFIX}). Use L{LocalizeVirtualPath} to
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undo the process. Virtual paths are meant to be transported via RPC.
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"""
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assert os.path.isabs(path)
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if _noderoot:
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return _VIRT_PATH_PREFIX + _RemoveNodePrefix(path, _noderoot=_noderoot)
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else:
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return path
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def LocalizeVirtualPath(path, _noderoot=_VIRT_NODEROOT): |
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"""Localizes a virtual path.
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A "virtualized" path consists of a prefix (L{LocalizeVirtualPath}) and a
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local path. This function adds the node-specific directory to the local path.
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Virtual paths are meant to be transported via RPC.
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"""
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assert os.path.isabs(path)
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if _noderoot:
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if path.startswith(_VIRT_PATH_PREFIX):
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return AddNodePrefix(path[len(_VIRT_PATH_PREFIX):], _noderoot=_noderoot) |
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else:
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raise RuntimeError("Path '%s' is not a virtual path" % path) |
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else:
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return path
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