Merge branch 'stable-2.16' into stable-2.17
[ganeti-github.git] / lib / vcluster.py
1 #
2 #
3
4 # Copyright (C) 2012 Google Inc.
5 # All rights reserved.
6 #
7 # Redistribution and use in source and binary forms, with or without
8 # modification, are permitted provided that the following conditions are
9 # met:
10 #
11 # 1. Redistributions of source code must retain the above copyright notice,
12 # this list of conditions and the following disclaimer.
13 #
14 # 2. Redistributions in binary form must reproduce the above copyright
15 # notice, this list of conditions and the following disclaimer in the
16 # documentation and/or other materials provided with the distribution.
17 #
18 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
19 # IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20 # TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
22 # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
23 # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
24 # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
25 # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
26 # LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27 # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 from ganeti import _constants
43 # cannot use constants, as this would cause a circular import
44
45
46 ETC_HOSTS = _constants.V_CLUSTER_ETC_HOSTS
47
48 _VIRT_PATH_PREFIX = _constants.V_CLUSTER_VIRT_PATH_PREFIX
49 _ROOTDIR_ENVNAME = _constants.V_CLUSTER_ROOTDIR_ENVNAME
50 _HOSTNAME_ENVNAME = _constants.V_CLUSTER_HOSTNAME_ENVNAME
51
52 #: List of paths which shouldn't be virtualized
53 _VPATH_WHITELIST = _constants.V_CLUSTER_VPATH_WHITELIST
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), "Not normalized: " + 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), "Path not absolute: " + path
204
205 if _noderoot:
206 result = "%s/%s" % (_noderoot, path)
207 else:
208 result = path
209
210 assert os.path.isabs(result), "Path not absolute: " + path
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), "Path not absolute: " + 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), "Path not absolute: " + path
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), "Path not absolute: " + 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), "Path not absolute: " + 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