Source Code for Module ganeti.vcluster

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 29   
 30   
 31  """Module containing utilities for virtual clusters. 
 32   
 33  Most functions manipulate file system paths and are no-ops when the environment 
 34  variables C{GANETI_ROOTDIR} and C{GANETI_HOSTNAME} are not set. See the 
 35  functions' docstrings for details. 
 36   
 37  """ 
 38   
 39  import os 
 40   
 41  from ganeti import compat 
 42   
 43   
 44  ETC_HOSTS = "/etc/hosts" 
 45   
 46  _VIRT_PATH_PREFIX = "/###-VIRTUAL-PATH-###," 
 47  _ROOTDIR_ENVNAME = "GANETI_ROOTDIR" 
 48  _HOSTNAME_ENVNAME = "GANETI_HOSTNAME" 
 49   
 50  #: List of paths which shouldn't be virtualized 
 51  _VPATH_WHITELIST = compat.UniqueFrozenset([ 
 52    ETC_HOSTS, 
 53    ]) 
 54   
 55   
 56 -def _GetRootDirectory(envname): 
 57    """Retrieves root directory from an environment variable. 
 58   
 59    @type envname: string 
 60    @param envname: Environment variable name 
 61    @rtype: string 
 62    @return: Root directory (can be empty) 
 63   
 64    """ 
 65    path = os.getenv(envname) 
 66   
 67    if path: 
 68      if not os.path.isabs(path): 
 69        raise RuntimeError("Root directory in '%s' must be absolute: %s" % 
 70                           (envname, path)) 
 71      return os.path.normpath(path) 
 72   
 73    return "" 
 74   
 75   
 76 -def _GetHostname(envname): 
 77    """Retrieves virtual hostname from an environment variable. 
 78   
 79    @type envname: string 
 80    @param envname: Environment variable name 
 81    @rtype: string 
 82    @return: Host name (can be empty) 
 83   
 84    """ 
 85    return os.getenv(envname, default="") 
 86   
 87   
 88 -def _CheckHostname(hostname): 
 89    """Very basic check for hostnames. 
 90   
 91    @type hostname: string 
 92    @param hostname: Hostname 
 93   
 94    """ 
 95    if os.path.basename(hostname) != hostname: 
 96      raise RuntimeError("Hostname '%s' can not be used for a file system" 
 97                         " path" % hostname) 
 98   
 99   
100 -def _PreparePaths(rootdir, hostname): 
101    """Checks if the root directory and hostname are acceptable. 
102   
103    The (node-specific) root directory must have the hostname as its last 
104    component. The parent directory then becomes the cluster-wide root directory. 
105    This is necessary as some components must be able to predict the root path on 
106    a remote node (e.g. copying files via scp). 
107   
108    @type rootdir: string 
109    @param rootdir: Root directory (from environment) 
110    @type hostname: string 
111    @param hostname: Hostname (from environment) 
112    @rtype: tuple; (string, string, string or None) 
113    @return: Tuple containing cluster-global root directory, node root directory 
114      and virtual hostname 
115   
116    """ 
117    if bool(rootdir) ^ bool(hostname): 
118      raise RuntimeError("Both root directory and hostname must be specified" 
119                         " using the environment variables %s and %s" % 
120                         (_ROOTDIR_ENVNAME, _HOSTNAME_ENVNAME)) 
121   
122    if rootdir: 
123      assert rootdir == os.path.normpath(rootdir) 
124   
125      _CheckHostname(hostname) 
126   
127      if os.path.basename(rootdir) != hostname: 
128        raise RuntimeError("Last component of root directory ('%s') must match" 
129                           " hostname ('%s')" % (rootdir, hostname)) 
130   
131      return (os.path.dirname(rootdir), rootdir, hostname) 
132    else: 
133      return ("", "", None) 
134   
135   
136  (_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME) = \ 
137    _PreparePaths(_GetRootDirectory(_ROOTDIR_ENVNAME), 
138                  _GetHostname(_HOSTNAME_ENVNAME)) 
139   
140   
141  assert (compat.all([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME]) or 
142          not compat.any([_VIRT_BASEDIR, _VIRT_NODEROOT, _VIRT_HOSTNAME])) 
143   
144   
145 -def GetVirtualHostname(): 
146    """Returns the virtual hostname. 
147   
148    @rtype: string or L{None} 
149   
150    """ 
151    return _VIRT_HOSTNAME 
152   
153   
154 -def MakeNodeRoot(base, node_name): 
155    """Appends a node name to the base directory. 
156   
157    """ 
158    _CheckHostname(node_name) 
159    return os.path.normpath("%s/%s" % (base, node_name)) 
160   
161   
162 -def ExchangeNodeRoot(node_name, filename, 
163                       _basedir=_VIRT_BASEDIR, _noderoot=_VIRT_NODEROOT): 
164    """Replaces the node-specific root directory in a path. 
165   
166    Replaces it with the root directory for another node. Assuming 
167    C{/tmp/vcluster/node1} is the root directory for C{node1}, the result will be 
168    C{/tmp/vcluster/node3} for C{node3} (as long as a root directory is specified 
169    in the environment). 
170   
171    """ 
172    if _basedir: 
173      pure = _RemoveNodePrefix(filename, _noderoot=_noderoot) 
174      result = "%s/%s" % (MakeNodeRoot(_basedir, node_name), pure) 
175    else: 
176      result = filename 
177   
178    return os.path.normpath(result) 
179   
180   
181 -def EnvironmentForHost(hostname, _basedir=_VIRT_BASEDIR): 
182    """Returns the environment variables for a host. 
183   
184    """ 
185    if _basedir: 
186      return { 
187        _ROOTDIR_ENVNAME: MakeNodeRoot(_basedir, hostname), 
188        _HOSTNAME_ENVNAME: hostname, 
189        } 
190    else: 
191      return {} 
192   
193   
194 -def AddNodePrefix(path, _noderoot=_VIRT_NODEROOT): 
195    """Adds a node-specific prefix to a path in a virtual cluster. 
196   
197    Returned path includes user-specified root directory if specified in 
198    environment. As an example, the path C{/var/lib/ganeti} becomes 
199    C{/tmp/vcluster/node1/var/lib/ganeti} if C{/tmp/vcluster/node1} is the root 
200    directory specified in the environment. 
201   
202    """ 
203    assert os.path.isabs(path) 
204   
205    if _noderoot: 
206      result = "%s/%s" % (_noderoot, path) 
207    else: 
208      result = path 
209   
210    assert os.path.isabs(result) 
211   
212    return os.path.normpath(result) 
213   
214   
215 -def _RemoveNodePrefix(path, _noderoot=_VIRT_NODEROOT): 
216    """Removes the node-specific prefix from a path. 
217   
218    This is the opposite of L{AddNodePrefix} and removes a node-local prefix 
219    path. 
220   
221    """ 
222    assert os.path.isabs(path) 
223   
224    norm_path = os.path.normpath(path) 
225   
226    if _noderoot: 
227      # Make sure path is actually below node root 
228      norm_root = os.path.normpath(_noderoot) 
229      root_with_sep = "%s%s" % (norm_root, os.sep) 
230      prefix = os.path.commonprefix([root_with_sep, norm_path]) 
231   
232      if prefix == root_with_sep: 
233        result = norm_path[len(norm_root):] 
234      else: 
235        raise RuntimeError("Path '%s' is not below node root '%s'" % 
236                           (path, _noderoot)) 
237    else: 
238      result = norm_path 
239   
240    assert os.path.isabs(result) 
241   
242    return result 
243   
244   
245 -def MakeVirtualPath(path, _noderoot=_VIRT_NODEROOT): 
246    """Virtualizes a path. 
247   
248    A path is "virtualized" by stripping it of its node-specific directory and 
249    prepending a prefix (L{_VIRT_PATH_PREFIX}). Use L{LocalizeVirtualPath} to 
250    undo the process. Virtual paths are meant to be transported via RPC. 
251   
252    """ 
253    assert os.path.isabs(path) 
254   
255    if _noderoot and path not in _VPATH_WHITELIST: 
256      return _VIRT_PATH_PREFIX + _RemoveNodePrefix(path, _noderoot=_noderoot) 
257    else: 
258      return path 
259   
260   
261 -def LocalizeVirtualPath(path, _noderoot=_VIRT_NODEROOT): 
262    """Localizes a virtual path. 
263   
264    A "virtualized" path consists of a prefix (L{LocalizeVirtualPath}) and a 
265    local path. This function adds the node-specific directory to the local path. 
266    Virtual paths are meant to be transported via RPC. 
267   
268    """ 
269    assert os.path.isabs(path) 
270   
271    if _noderoot and path not in _VPATH_WHITELIST: 
272      if path.startswith(_VIRT_PATH_PREFIX): 
273        return AddNodePrefix(path[len(_VIRT_PATH_PREFIX):], _noderoot=_noderoot) 
274      else: 
275        raise RuntimeError("Path '%s' is not a virtual path" % path) 
276    else: 
277      return path 
278