4 # Copyright (C) 2012 Google Inc.
6 # This program is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; either version 2 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful, but
12 # WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 # General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program; if not, write to the Free Software
18 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
22 """Module containing utilities for virtual clusters.
24 Most functions manipulate file system paths and are no-ops when the environment
25 variables C{GANETI_ROOTDIR} and C{GANETI_HOSTNAME} are not set. See the
26 functions' docstrings for details.
32 from ganeti import compat
35 ETC_HOSTS = "/etc/hosts"
37 _VIRT_PATH_PREFIX = "/###-VIRTUAL-PATH-###,"
38 _ROOTDIR_ENVNAME = "GANETI_ROOTDIR"
39 _HOSTNAME_ENVNAME = "GANETI_HOSTNAME"
41 #: List of paths which shouldn't be virtualized
42 _VPATH_WHITELIST = compat.UniqueFrozenset([
47 def _GetRootDirectory(envname):
48 """Retrieves root directory from an environment variable.
51 @param envname: Environment variable name
53 @return: Root directory (can be empty)
56 path = os.getenv(envname)
59 if not os.path.isabs(path):
60 raise RuntimeError("Root directory in '%s' must be absolute: %s" %
62 return os.path.normpath(path)
67 def _GetHostname(envname):
68 """Retrieves virtual hostname from an environment variable.
71 @param envname: Environment variable name
73 @return: Host name (can be empty)
76 return os.getenv(envname, default="")
79 def _CheckHostname(hostname):
80 """Very basic check for hostnames.
82 @type hostname: string
83 @param hostname: Hostname
86 if os.path.basename(hostname) != hostname:
87 raise RuntimeError("Hostname '%s' can not be used for a file system"
91 def _PreparePaths(rootdir, hostname):
92 """Checks if the root directory and hostname are acceptable.
94 The (node-specific) root directory must have the hostname as its last
95 component. The parent directory then becomes the cluster-wide root directory.
96 This is necessary as some components must be able to predict the root path on
97 a remote node (e.g. copying files via scp).
100 @param rootdir: Root directory (from environment)
101 @type hostname: string
102 @param hostname: Hostname (from environment)
103 @rtype: tuple; (string, string, string or None)
104 @return: Tuple containing cluster-global root directory, node root directory
108 if bool(rootdir) ^ bool(hostname):
109 raise RuntimeError("Both root directory and hostname must be specified"
110 " using the environment variables %s and %s" %
111 (_ROOTDIR_ENVNAME, _HOSTNAME_ENVNAME))
114 assert rootdir == os.path.normpath(rootdir)
116 _CheckHostname(hostname)
118 if os.path.basename(rootdir) != hostname:
119 raise RuntimeError("Last component of root directory ('%s') must match"
120 " hostname ('%s')" % (rootdir, hostname))
122 return (os.path.dirname(rootdir), rootdir, hostname)
124 return ("", "", None)
127 (_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME) = \
128 _PreparePaths(_GetRootDirectory(_ROOTDIR_ENVNAME),
129 _GetHostname(_HOSTNAME_ENVNAME))
132 assert (compat.all([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]) or
133 not compat.any([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]))
136 def GetVirtualHostname():
137 """Returns the virtual hostname.
139 @rtype: string or L{None}
142 return _VIRT_HOSTNAME
145 def MakeNodeRoot(base, node_name):
146 """Appends a node name to the base directory.
149 _CheckHostname(node_name)
150 return os.path.normpath("%s/%s" % (base, node_name))
153 def ExchangeNodeRoot(node_name, filename,
154 _basedir=_VIRT_BASEDIR, _noderoot=_VIRT_NODEROOT):
155 """Replaces the node-specific root directory in a path.
157 Replaces it with the root directory for another node. Assuming
158 C{/tmp/vcluster/node1} is the root directory for C{node1}, the result will be
159 C{/tmp/vcluster/node3} for C{node3} (as long as a root directory is specified
164 pure = _RemoveNodePrefix(filename, _noderoot=_noderoot)
165 result = "%s/%s" % (MakeNodeRoot(_basedir, node_name), pure)
169 return os.path.normpath(result)
172 def EnvironmentForHost(hostname, _basedir=_VIRT_BASEDIR):
173 """Returns the environment variables for a host.
178 _ROOTDIR_ENVNAME: MakeNodeRoot(_basedir, hostname),
179 _HOSTNAME_ENVNAME: hostname,
185 def AddNodePrefix(path, _noderoot=_VIRT_NODEROOT):
186 """Adds a node-specific prefix to a path in a virtual cluster.
188 Returned path includes user-specified root directory if specified in
189 environment. As an example, the path C{/var/lib/ganeti} becomes
190 C{/tmp/vcluster/node1/var/lib/ganeti} if C{/tmp/vcluster/node1} is the root
191 directory specified in the environment.
194 assert os.path.isabs(path)
197 result = "%s/%s" % (_noderoot, path)
201 assert os.path.isabs(result)
203 return os.path.normpath(result)
206 def _RemoveNodePrefix(path, _noderoot=_VIRT_NODEROOT):
207 """Removes the node-specific prefix from a path.
209 This is the opposite of L{AddNodePrefix} and removes a node-local prefix
213 assert os.path.isabs(path)
215 norm_path = os.path.normpath(path)
218 # Make sure path is actually below node root
219 norm_root = os.path.normpath(_noderoot)
220 root_with_sep = "%s%s" % (norm_root, os.sep)
221 prefix = os.path.commonprefix([root_with_sep, norm_path])
223 if prefix == root_with_sep:
224 result = norm_path[len(norm_root):]
226 raise RuntimeError("Path '%s' is not below node root '%s'" %
231 assert os.path.isabs(result)
236 def MakeVirtualPath(path, _noderoot=_VIRT_NODEROOT):
237 """Virtualizes a path.
239 A path is "virtualized" by stripping it of its node-specific directory and
240 prepending a prefix (L{_VIRT_PATH_PREFIX}). Use L{LocalizeVirtualPath} to
241 undo the process. Virtual paths are meant to be transported via RPC.
244 assert os.path.isabs(path)
246 if _noderoot and path not in _VPATH_WHITELIST:
247 return _VIRT_PATH_PREFIX + _RemoveNodePrefix(path, _noderoot=_noderoot)
252 def LocalizeVirtualPath(path, _noderoot=_VIRT_NODEROOT):
253 """Localizes a virtual path.
255 A "virtualized" path consists of a prefix (L{LocalizeVirtualPath}) and a
256 local path. This function adds the node-specific directory to the local path.
257 Virtual paths are meant to be transported via RPC.
260 assert os.path.isabs(path)
262 if _noderoot and path not in _VPATH_WHITELIST:
263 if path.startswith(_VIRT_PATH_PREFIX):
264 return AddNodePrefix(path[len(_VIRT_PATH_PREFIX):], _noderoot=_noderoot)
266 raise RuntimeError("Path '%s' is not a virtual path" % path)