python: Added a module with abstracted tools for both ashd-wsgi and scgi-wsgi.
[ashd.git] / python / ashd / wsgidir.py
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1"""WSGI handler for serving chained WSGI modules from physical files
2
3The WSGI handler in this module ensures that the SCRIPT_FILENAME
4variable is properly set in every request and points out a file that
5exists and is readable. It then dispatches the request in one of two
6ways: If the header X-Ash-Python-Handler is set in the request, its
7value is used as the name of a handler object to dispatch the request
8to; otherwise, the file extension of the SCRIPT_FILENAME is used to
9determine the handler object.
10
11The name of a handler object is specified as a string, which is split
12along its last constituent dot. The part left of the dot is the name
13of a module, which is imported; and the part right of the dot is the
14name of an object in that module, which should be a callable adhering
15to the WSGI specification. Alternatively, the module part may be
16omitted (such that the name is a string with no dots), in which case
17the handler object is looked up from this module.
18
19By default, this module will handle files with the extensions `.wsgi'
20or `.wsgi2' using the `chain' handler, which chainloads such files and
21runs them as independent WSGI applications. See its documentation for
22details.
23
24This module itself contains both an `application' and a `wmain'
25object. If this module is used by ashd-wsgi(1) or scgi-wsgi(1) so that
26its wmain function is called, arguments can be specified to it to
27install handlers for other file extensions. Such arguments take the
28form `.EXT=HANDLER', where EXT is the file extension to be handled,
29and HANDLER is a handler name, as described above. For example, the
30argument `.fpy=my.module.foohandler' can be given to pass requests for
31`.fpy' files to the function `foohandler' in the module `my.module'
32(which must, of course, be importable). When writing such handler
33functions, you may want to use the getmod() function in this module.
34"""
35
36import sys, os, threading, types, logging, getopt
37import wsgiutil
38
39__all__ = ["application", "wmain", "getmod", "cachedmod", "chain"]
40
41log = logging.getLogger("wsgidir")
42
43class cachedmod(object):
44 """Cache entry for modules loaded by getmod()
45
46 Instances of this class are returned by the getmod()
47 function. They contain three data attributes:
48 * mod - The loaded module
49 * lock - A threading.Lock object, which can be used for
50 manipulating this instance in a thread-safe manner
51 * mtime - The time the file was last modified
52
53 Additional data attributes can be arbitrarily added for recording
54 any meta-data about the module.
55 """
56 def __init__(self, mod = None, mtime = -1):
57 self.lock = threading.Lock()
58 self.mod = mod
59 self.mtime = mtime
60
61modcache = {}
62cachelock = threading.Lock()
63
64def mangle(path):
65 ret = ""
66 for c in path:
67 if c.isalnum():
68 ret += c
69 else:
70 ret += "_"
71 return ret
72
73def getmod(path):
74 """Load the given file as a module, caching it appropriately
75
76 The given file is loaded and compiled into a Python module. The
77 compiled module is cached and returned upon subsequent requests
78 for the same file, unless the file has changed (as determined by
79 its mtime), in which case the cached module is discarded and the
80 new file contents are reloaded in its place.
81
82 The return value is an instance of the cachedmod class, which can
83 be used for locking purposes and for storing arbitrary meta-data
84 about the module. See its documentation for details.
85 """
86 sb = os.stat(path)
87 cachelock.acquire()
88 try:
89 if path in modcache:
90 entry = modcache[path]
91 else:
92 entry = [threading.Lock(), None]
93 modcache[path] = entry
94 finally:
95 cachelock.release()
96 entry[0].acquire()
97 try:
98 if entry[1] is None or sb.st_mtime > entry[1].mtime:
99 f = open(path, "r")
100 try:
101 text = f.read()
102 finally:
103 f.close()
104 code = compile(text, path, "exec")
105 mod = types.ModuleType(mangle(path))
106 mod.__file__ = path
107 exec code in mod.__dict__
108 entry[1] = cachedmod(mod, sb.st_mtime)
109 return entry[1]
110 finally:
111 entry[0].release()
112
113def importlocal(filename):
114 import inspect
115 cf = inspect.currentframe()
116 if cf is None: raise ImportError("could not get current frame")
117 if cf.f_back is None: raise ImportError("could not get caller frame")
118 cfile = cf.f_back.f_code.co_filename
119 if not os.path.exists(cfile):
120 raise ImportError("caller is not in a proper file")
121 path = os.path.realpath(os.path.join(os.path.dirname(cfile), filename))
122 if '.' not in os.path.basename(path):
123 for ext in [".pyl", ".py"]:
124 if os.path.exists(path + ext):
125 path += ext
126 break
127 else:
128 raise ImportError("could not resolve file: " + filename)
129 else:
130 if not os.path.exists(cfile):
131 raise ImportError("no such file: " + filename)
132 return getmod(path).mod
133
134class handler(object):
135 def __init__(self):
136 self.lock = threading.Lock()
137 self.handlers = {}
138 self.exts = {}
139 self.addext("wsgi", "chain")
140 self.addext("wsgi2", "chain")
141
142 def resolve(self, name):
143 self.lock.acquire()
144 try:
145 if name in self.handlers:
146 return self.handlers[name]
147 p = name.rfind('.')
148 if p < 0:
149 return globals()[name]
150 mname = name[:p]
151 hname = name[p + 1:]
152 mod = __import__(mname, fromlist = ["dummy"])
153 ret = getattr(mod, hname)
154 self.handlers[name] = ret
155 return ret
156 finally:
157 self.lock.release()
158
159 def addext(self, ext, handler):
160 self.exts[ext] = self.resolve(handler)
161
162 def handle(self, env, startreq):
163 if not "SCRIPT_FILENAME" in env:
164 log.error("wsgidir called without SCRIPT_FILENAME set")
165 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.")
166 path = env["SCRIPT_FILENAME"]
167 if not os.access(path, os.R_OK):
168 log.error("%s: not readable" % path)
169 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.")
170 if "HTTP_X_ASH_PYTHON_HANDLER" in env:
171 try:
172 handler = self.resolve(env["HTTP_X_ASH_PYTHON_HANDLER"])
173 except Exception:
174 log.error("could not load handler %s" % env["HTTP_X_ASH_PYTHON_HANDLER"], exc_info=sys.exc_info())
175 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.")
176 else:
177 base = os.path.basename(path)
178 p = base.rfind('.')
179 if p < 0:
180 log.error("wsgidir called with neither X-Ash-Python-Handler nor a file extension: %s" % path)
181 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.")
182 ext = base[p + 1:]
183 if not ext in self.exts:
184 log.error("unregistered file extension: %s" % ext)
185 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.")
186 handler = self.exts[ext]
187 return handler(env, startreq)
188
189def wmain(*argv):
190 """Main function for ashd(7)-compatible WSGI handlers
191
192 Returns the `application' function. If any arguments are given,
193 they are parsed according to the module documentation.
194 """
195 hnd = handler()
196 ret = hnd.handle
197
198 opts, args = getopt.getopt(argv, "V")
199 for o, a in opts:
200 if o == "-V":
201 import wsgiref.validate
202 ret = wsgiref.validate.validator(ret)
203
204 for arg in args:
205 if arg[0] == '.':
206 p = arg.index('=')
207 hnd.addext(arg[1:p], arg[p + 1:])
208 return ret
209
210def chain(env, startreq):
211 """Chain-loading WSGI handler
212
213 This handler loads requested files, compiles them and loads them
214 into their own modules. The compiled modules are cached and reused
215 until the file is modified, in which case the previous module is
216 discarded and the new file contents are loaded into a new module
217 in its place. When chaining such modules, an object named `wmain'
218 is first looked for and called with no arguments if found. The
219 object it returns is then used as the WSGI application object for
220 that module, which is reused until the module is reloaded. If
221 `wmain' is not found, an object named `application' is looked for
222 instead. If found, it is used directly as the WSGI application
223 object.
224 """
225 path = env["SCRIPT_FILENAME"]
226 try:
227 mod = getmod(path)
228 except Exception:
229 log.error("Exception occurred when loading %s" % path, exc_info=sys.exc_info())
230 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "Could not load WSGI handler.")
231 entry = None
232 if mod is not None:
233 mod.lock.acquire()
234 try:
235 if hasattr(mod, "entry"):
236 entry = mod.entry
237 else:
238 if hasattr(mod.mod, "wmain"):
239 entry = mod.mod.wmain()
240 elif hasattr(mod.mod, "application"):
241 entry = mod.mod.application
242 mod.entry = entry
243 finally:
244 mod.lock.release()
245 if entry is not None:
246 return entry(env, startreq)
247 return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "Invalid WSGI handler.")
248
249application = handler().handle