Source Code for Module ganeti.vcluster

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2012 Google Inc. 
  5  # 
  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. 
 10  # 
 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. 
 15  # 
 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 
 19  # 02110-1301, USA. 
 20   
 21   
 22  """Module containing utilities for virtual clusters. 
 23   
 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. 
 27   
 28  """ 
 29   
 30  import os 
 31   
 32  from ganeti import compat 
 33   
 34   
 35  ETC_HOSTS = "/etc/hosts" 
 36   
 37  _VIRT_PATH_PREFIX = "/###-VIRTUAL-PATH-###," 
 38  _ROOTDIR_ENVNAME = "GANETI_ROOTDIR" 
 39  _HOSTNAME_ENVNAME = "GANETI_HOSTNAME" 
 40   
 41  #: List of paths which shouldn't be virtualized 
 42  _VPATH_WHITELIST = compat.UniqueFrozenset([ 
 43    ETC_HOSTS, 
 44    ]) 
 45   
 46   
 47 -def _GetRootDirectory(envname): 
 48    """Retrieves root directory from an environment variable. 
 49   
 50    @type envname: string 
 51    @param envname: Environment variable name 
 52    @rtype: string 
 53    @return: Root directory (can be empty) 
 54   
 55    """ 
 56    path = os.getenv(envname) 
 57   
 58    if path: 
 59      if not os.path.isabs(path): 
 60        raise RuntimeError("Root directory in '%s' must be absolute: %s" % 
 61                           (envname, path)) 
 62      return os.path.normpath(path) 
 63   
 64    return "" 
 65   
 66   
 67 -def _GetHostname(envname): 
 68    """Retrieves virtual hostname from an environment variable. 
 69   
 70    @type envname: string 
 71    @param envname: Environment variable name 
 72    @rtype: string 
 73    @return: Host name (can be empty) 
 74   
 75    """ 
 76    return os.getenv(envname, default="") 
 77   
 78   
 79 -def _CheckHostname(hostname): 
 80    """Very basic check for hostnames. 
 81   
 82    @type hostname: string 
 83    @param hostname: Hostname 
 84   
 85    """ 
 86    if os.path.basename(hostname) != hostname: 
 87      raise RuntimeError("Hostname '%s' can not be used for a file system" 
 88                         " path" % hostname) 
 89   
 90   
 91 -def _PreparePaths(rootdir, hostname): 
 92    """Checks if the root directory and hostname are acceptable. 
 93   
 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). 
 98   
 99    @type rootdir: string 
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 
105      and virtual hostname 
106   
107    """ 
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)) 
112   
113    if rootdir: 
114      assert rootdir == os.path.normpath(rootdir) 
115   
116      _CheckHostname(hostname) 
117   
118      if os.path.basename(rootdir) != hostname: 
119        raise RuntimeError("Last component of root directory ('%s') must match" 
120                           " hostname ('%s')" % (rootdir, hostname)) 
121   
122      return (os.path.dirname(rootdir), rootdir, hostname) 
123    else: 
124      return ("", "", None) 
125   
126   
127  (_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME) = \ 
128    _PreparePaths(_GetRootDirectory(_ROOTDIR_ENVNAME), 
129                  _GetHostname(_HOSTNAME_ENVNAME)) 
130   
131   
132  assert (compat.all([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]) or 
133          not compat.any([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME])) 
134   
135   
136 -def GetVirtualHostname(): 
137    """Returns the virtual hostname. 
138   
139    @rtype: string or L{None} 
140   
141    """ 
142    return _VIRT_HOSTNAME 
143   
144   
145 -def MakeNodeRoot(base, node_name): 
146    """Appends a node name to the base directory. 
147   
148    """ 
149    _CheckHostname(node_name) 
150    return os.path.normpath("%s/%s" % (base, node_name)) 
151   
152   
153 -def ExchangeNodeRoot(node_name, filename, 
154                       _basedir=_VIRT_BASEDIR, _noderoot=_VIRT_NODEROOT): 
155    """Replaces the node-specific root directory in a path. 
156   
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 
160    in the environment). 
161   
162    """ 
163    if _basedir: 
164      pure = _RemoveNodePrefix(filename, _noderoot=_noderoot) 
165      result = "%s/%s" % (MakeNodeRoot(_basedir, node_name), pure) 
166    else: 
167      result = filename 
168   
169    return os.path.normpath(result) 
170   
171   
172 -def EnvironmentForHost(hostname, _basedir=_VIRT_BASEDIR): 
173    """Returns the environment variables for a host. 
174   
175    """ 
176    if _basedir: 
177      return { 
178        _ROOTDIR_ENVNAME: MakeNodeRoot(_basedir, hostname), 
179        _HOSTNAME_ENVNAME: hostname, 
180        } 
181    else: 
182      return {} 
183   
184   
185 -def AddNodePrefix(path, _noderoot=_VIRT_NODEROOT): 
186    """Adds a node-specific prefix to a path in a virtual cluster. 
187   
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. 
192   
193    """ 
194    assert os.path.isabs(path) 
195   
196    if _noderoot: 
197      result = "%s/%s" % (_noderoot, path) 
198    else: 
199      result = path 
200   
201    assert os.path.isabs(result) 
202   
203    return os.path.normpath(result) 
204   
205   
206 -def _RemoveNodePrefix(path, _noderoot=_VIRT_NODEROOT): 
207    """Removes the node-specific prefix from a path. 
208   
209    This is the opposite of L{AddNodePrefix} and removes a node-local prefix 
210    path. 
211   
212    """ 
213    assert os.path.isabs(path) 
214   
215    norm_path = os.path.normpath(path) 
216   
217    if _noderoot: 
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]) 
222   
223      if prefix == root_with_sep: 
224        result = norm_path[len(norm_root):] 
225      else: 
226        raise RuntimeError("Path '%s' is not below node root '%s'" % 
227                           (path, _noderoot)) 
228    else: 
229      result = norm_path 
230   
231    assert os.path.isabs(result) 
232   
233    return result 
234   
235   
236 -def MakeVirtualPath(path, _noderoot=_VIRT_NODEROOT): 
237    """Virtualizes a path. 
238   
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. 
242   
243    """ 
244    assert os.path.isabs(path) 
245   
246    if _noderoot and path not in _VPATH_WHITELIST: 
247      return _VIRT_PATH_PREFIX + _RemoveNodePrefix(path, _noderoot=_noderoot) 
248    else: 
249      return path 
250   
251   
252 -def LocalizeVirtualPath(path, _noderoot=_VIRT_NODEROOT): 
253    """Localizes a virtual path. 
254   
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. 
258   
259    """ 
260    assert os.path.isabs(path) 
261   
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) 
265      else: 
266        raise RuntimeError("Path '%s' is not a virtual path" % path) 
267    else: 
268      return path 
269