| 1 | """WSGI handler for serving chained WSGI modules from physical files |
| 2 | |
| 3 | The WSGI handler in this module ensures that the SCRIPT_FILENAME |
| 4 | variable is properly set in every request and points out a file that |
| 5 | exists and is readable. It then dispatches the request in one of two |
| 6 | ways: If the header X-Ash-Python-Handler is set in the request, its |
| 7 | value is used as the name of a handler object to dispatch the request |
| 8 | to; otherwise, the file extension of the SCRIPT_FILENAME is used to |
| 9 | determine the handler object. |
| 10 | |
| 11 | The name of a handler object is specified as a string, which is split |
| 12 | along its last constituent dot. The part left of the dot is the name |
| 13 | of a module, which is imported; and the part right of the dot is the |
| 14 | name of an object in that module, which should be a callable adhering |
| 15 | to the WSGI specification. Alternatively, the module part may be |
| 16 | omitted (such that the name is a string with no dots), in which case |
| 17 | the handler object is looked up from this module. |
| 18 | |
| 19 | By default, this module will handle files with the extensions `.wsgi' |
| 20 | or `.wsgi2' using the `chain' handler, which chainloads such files and |
| 21 | runs them as independent WSGI applications. See its documentation for |
| 22 | details. |
| 23 | |
| 24 | This module itself contains both an `application' and a `wmain' |
| 25 | object. If this module is used by ashd-wsgi(1) or scgi-wsgi(1) so that |
| 26 | its wmain function is called, arguments can be specified to it to |
| 27 | install handlers for other file extensions. Such arguments take the |
| 28 | form `.EXT=HANDLER', where EXT is the file extension to be handled, |
| 29 | and HANDLER is a handler name, as described above. For example, the |
| 30 | argument `.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 |
| 33 | functions, you may want to use the getmod() function in this module. |
| 34 | """ |
| 35 | |
| 36 | import os, threading, types |
| 37 | import wsgiutil |
| 38 | |
| 39 | __all__ = ["application", "wmain", "getmod", "cachedmod", "chain"] |
| 40 | |
| 41 | class cachedmod(object): |
| 42 | """Cache entry for modules loaded by getmod() |
| 43 | |
| 44 | Instances of this class are returned by the getmod() |
| 45 | function. They contain three data attributes: |
| 46 | * mod - The loaded module |
| 47 | * lock - A threading.Lock object, which can be used for |
| 48 | manipulating this instance in a thread-safe manner |
| 49 | * mtime - The time the file was last modified |
| 50 | |
| 51 | Additional data attributes can be arbitrarily added for recording |
| 52 | any meta-data about the module. |
| 53 | """ |
| 54 | def __init__(self, mod = None, mtime = -1): |
| 55 | self.lock = threading.Lock() |
| 56 | self.mod = mod |
| 57 | self.mtime = mtime |
| 58 | |
| 59 | modcache = {} |
| 60 | cachelock = threading.Lock() |
| 61 | |
| 62 | def mangle(path): |
| 63 | ret = "" |
| 64 | for c in path: |
| 65 | if c.isalnum(): |
| 66 | ret += c |
| 67 | else: |
| 68 | ret += "_" |
| 69 | return ret |
| 70 | |
| 71 | def getmod(path): |
| 72 | """Load the given file as a module, caching it appropriately |
| 73 | |
| 74 | The given file is loaded and compiled into a Python module. The |
| 75 | compiled module is cached and returned upon subsequent requests |
| 76 | for the same file, unless the file has changed (as determined by |
| 77 | its mtime), in which case the cached module is discarded and the |
| 78 | new file contents are reloaded in its place. |
| 79 | |
| 80 | The return value is an instance of the cachedmod class, which can |
| 81 | be used for locking purposes and for storing arbitrary meta-data |
| 82 | about the module. See its documentation for details. |
| 83 | """ |
| 84 | sb = os.stat(path) |
| 85 | cachelock.acquire() |
| 86 | try: |
| 87 | if path in modcache: |
| 88 | entry = modcache[path] |
| 89 | else: |
| 90 | entry = [threading.Lock(), None] |
| 91 | modcache[path] = entry |
| 92 | finally: |
| 93 | cachelock.release() |
| 94 | entry[0].acquire() |
| 95 | try: |
| 96 | if entry[1] is None or sb.st_mtime > entry[1].mtime: |
| 97 | f = open(path, "r") |
| 98 | try: |
| 99 | text = f.read() |
| 100 | finally: |
| 101 | f.close() |
| 102 | code = compile(text, path, "exec") |
| 103 | mod = types.ModuleType(mangle(path)) |
| 104 | mod.__file__ = path |
| 105 | exec code in mod.__dict__ |
| 106 | entry[1] = cachedmod(mod, sb.st_mtime) |
| 107 | return entry[1] |
| 108 | finally: |
| 109 | entry[0].release() |
| 110 | |
| 111 | class handler(object): |
| 112 | def __init__(self): |
| 113 | self.lock = threading.Lock() |
| 114 | self.handlers = {} |
| 115 | self.exts = {} |
| 116 | self.addext("wsgi", "chain") |
| 117 | self.addext("wsgi2", "chain") |
| 118 | |
| 119 | def resolve(self, name): |
| 120 | self.lock.acquire() |
| 121 | try: |
| 122 | if name in self.handlers: |
| 123 | return self.handlers[name] |
| 124 | p = name.rfind('.') |
| 125 | if p < 0: |
| 126 | return globals()[name] |
| 127 | mname = name[:p] |
| 128 | hname = name[p + 1:] |
| 129 | mod = __import__(mname, fromlist = ["dummy"]) |
| 130 | ret = getattr(mod, hname) |
| 131 | self.handlers[name] = ret |
| 132 | return ret |
| 133 | finally: |
| 134 | self.lock.release() |
| 135 | |
| 136 | def addext(self, ext, handler): |
| 137 | self.exts[ext] = self.resolve(handler) |
| 138 | |
| 139 | def handle(self, env, startreq): |
| 140 | if not "SCRIPT_FILENAME" in env: |
| 141 | return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") |
| 142 | path = env["SCRIPT_FILENAME"] |
| 143 | if not os.access(path, os.R_OK): |
| 144 | return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") |
| 145 | if "HTTP_X_ASH_PYTHON_HANDLER" in env: |
| 146 | handler = self.resolve(env["HTTP_X_ASH_PYTHON_HANDLER"]) |
| 147 | else: |
| 148 | base = os.path.basename(path) |
| 149 | p = base.rfind('.') |
| 150 | if p < 0: |
| 151 | return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") |
| 152 | ext = base[p + 1:] |
| 153 | if not ext in self.exts: |
| 154 | return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") |
| 155 | handler = self.exts[ext] |
| 156 | return handler(env, startreq) |
| 157 | |
| 158 | def wmain(*argv): |
| 159 | """Main function for ashd(7)-compatible WSGI handlers |
| 160 | |
| 161 | Returns the `application' function. If any arguments are given, |
| 162 | they are parsed according to the module documentation. |
| 163 | """ |
| 164 | ret = handler() |
| 165 | for arg in argv: |
| 166 | if arg[0] == '.': |
| 167 | p = arg.index('=') |
| 168 | ret.addext(arg[1:p], arg[p + 1:]) |
| 169 | return ret.handle |
| 170 | |
| 171 | def chain(env, startreq): |
| 172 | """Chain-loading WSGI handler |
| 173 | |
| 174 | This handler loads requested files, compiles them and loads them |
| 175 | into their own modules. The compiled modules are cached and reused |
| 176 | until the file is modified, in which case the previous module is |
| 177 | discarded and the new file contents are loaded into a new module |
| 178 | in its place. When chaining such modules, an object named `wmain' |
| 179 | is first looked for and called with no arguments if found. The |
| 180 | object it returns is then used as the WSGI application object for |
| 181 | that module, which is reused until the module is reloaded. If |
| 182 | `wmain' is not found, an object named `application' is looked for |
| 183 | instead. If found, it is used directly as the WSGI application |
| 184 | object. |
| 185 | """ |
| 186 | path = env["SCRIPT_FILENAME"] |
| 187 | mod = getmod(path) |
| 188 | entry = None |
| 189 | if mod is not None: |
| 190 | mod.lock.acquire() |
| 191 | try: |
| 192 | if hasattr(mod, "entry"): |
| 193 | entry = mod.entry |
| 194 | else: |
| 195 | if hasattr(mod.mod, "wmain"): |
| 196 | entry = mod.mod.wmain() |
| 197 | elif hasattr(mod.mod, "application"): |
| 198 | entry = mod.mod.application |
| 199 | mod.entry = entry |
| 200 | finally: |
| 201 | mod.lock.release() |
| 202 | if entry is not None: |
| 203 | return entry(env, startreq) |
| 204 | return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "Invalid WSGI handler.") |
| 205 | |
| 206 | application = handler().handle |