Package ganeti :: Module vcluster
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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