X-Git-Url: http://www.dolda2000.com/gitweb/?p=ashd.git;a=blobdiff_plain;f=python%2Fashd%2Fwsgidir.py;h=991b9f6e08e5aceb462612398acfdd3c9183b1a6;hp=212c4b73ef4ca20a2bd1e486e42ac2b5851da4d7;hb=7fe08a6fe8661e0429e2f2da599bdf84523dc5d5;hpb=36ea06a63bb12fed3406b3e7bbbcd87633877045 diff --git a/python/ashd/wsgidir.py b/python/ashd/wsgidir.py index 212c4b7..991b9f6 100644 --- a/python/ashd/wsgidir.py +++ b/python/ashd/wsgidir.py @@ -1,6 +1,65 @@ +"""WSGI handler for serving chained WSGI modules from physical files + +The WSGI handler in this module examines the SCRIPT_FILENAME variable +of the requests it handles -- that is, the physical file corresponding +to the request, as determined by the webserver -- determining what to +do with the request based on the extension of that file. + +By default, it handles files named `.wsgi' by compiling them into +Python modules and using them, in turn, as chained WSGI handlers, but +handlers for other extensions can be installed as well. + +When handling `.wsgi' files, the compiled modules are cached and +reused until the file is modified, in which case the previous module +is discarded and the new file contents are loaded into a new module in +its place. When chaining such modules, an object named `wmain' is +first looked for and called with no arguments if found. The object it +returns is then used as the WSGI application object for that module, +which is reused until the module is reloaded. If `wmain' is not found, +an object named `application' is looked for instead. If found, it is +used directly as the WSGI application object. + +This module itself contains both an `application' and a `wmain' +object. If this module is used by ashd-wsgi(1) or scgi-wsgi(1) so that +its wmain function is called, arguments can be specified to it to +install handlers for other file extensions. Such arguments take the +form `.EXT=MODULE.HANDLER', where EXT is the file extension to be +handled, and the MODULE.HANDLER string is treated by splitting it +along its last constituent dot. The part left of the dot is the name +of a module which is imported, and the part right of the dot is the +name of an object in that module, which should be a callable adhering +to the WSGI specification. When called, this module will have made +sure that the WSGI environment contains the SCRIPT_FILENAME parameter +and that it is properly working. For example, the argument +`.fpy=my.module.foohandler' can be given to pass requests for `.fpy' +files to the function `foohandler' in the module `my.module' (which +must, of course, be importable). When writing such handler functions, +you will probably want to use the getmod() function in this module. +""" + import os, threading, types import wsgiutil +__all__ = ["application", "wmain", "getmod", "cachedmod"] + +class cachedmod(object): + """Cache entry for modules loaded by getmod() + + Instances of this class are returned by the getmod() + function. They contain three data attributes: + * mod - The loaded module + * lock - A threading.Lock object, which can be used for + manipulating this instance in a thread-safe manner + * mtime - The time the file was last modified + + Additional data attributes can be arbitrarily added for recording + any meta-data about the module. + """ + def __init__(self, mod = None, mtime = -1): + self.lock = threading.Lock() + self.mod = mod + self.mtime = mtime + exts = {} modcache = {} cachelock = threading.Lock() @@ -15,37 +74,80 @@ def mangle(path): return ret def getmod(path): + """Load the given file as a module, caching it appropriately + + The given file is loaded and compiled into a Python module. The + compiled module is cached and returned upon subsequent requests + for the same file, unless the file has changed (as determined by + its mtime), in which case the cached module is discarded and the + new file contents are reloaded in its place. + + The return value is an instance of the cachedmod class, which can + be used for locking purposes and for storing arbitrary meta-data + about the module. See its documentation for details. + """ sb = os.stat(path) cachelock.acquire() try: if path in modcache: - mod, mtime = modcache[path] - if sb.st_mtime <= mtime: - return mod - f = open(path) - try: - text = f.read() - finally: - f.close() - code = compile(text, path, "exec") - mod = types.ModuleType(mangle(path)) - mod.__file__ = path - exec code in mod.__dict__ - modcache[path] = mod, sb.st_mtime - return mod + entry = modcache[path] + else: + entry = cachedmod() + modcache[path] = entry finally: cachelock.release() + entry.lock.acquire() + try: + if entry.mod is None or sb.st_mtime > entry.mtime: + f = open(path, "r") + try: + text = f.read() + finally: + f.close() + code = compile(text, path, "exec") + mod = types.ModuleType(mangle(path)) + mod.__file__ = path + exec code in mod.__dict__ + entry.mod = mod + entry.mtime = sb.st_mtime + return entry + finally: + entry.lock.release() -def chain(path, env, startreq): +def chain(env, startreq): + path = env["SCRIPT_FILENAME"] mod = getmod(path) - if hasattr(mod, "wmain"): - return (mod.wmain())(env, startreq) - elif hasattr(mod, "application"): - return mod.application(env, startreq) + entry = None + if mod is not None: + mod.lock.acquire() + try: + if hasattr(mod, "entry"): + entry = mod.entry + else: + if hasattr(mod.mod, "wmain"): + entry = mod.mod.wmain() + elif hasattr(mod.mod, "application"): + entry = mod.mod.application + mod.entry = entry + finally: + mod.lock.release() + if entry is not None: + return entry(env, startreq) return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "Invalid WSGI handler.") exts["wsgi"] = chain +def addext(ext, handler): + p = handler.rindex('.') + mname = handler[:p] + hname = handler[p + 1:] + mod = __import__(mname, fromlist = ["dummy"]) + exts[ext] = getattr(mod, hname) + def application(env, startreq): + """WSGI handler function + + Handles WSGI requests as per the module documentation. + """ if not "SCRIPT_FILENAME" in env: return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") path = env["SCRIPT_FILENAME"] @@ -56,7 +158,16 @@ def application(env, startreq): ext = base[p + 1:] if not ext in exts: return wsgiutil.simpleerror(env, startreq, 500, "Internal Error", "The server is erroneously configured.") - return(exts[ext](path, env, startreq)) + return(exts[ext](env, startreq)) + +def wmain(*argv): + """Main function for ashd(7)-compatible WSGI handlers -def wmain(argv): + Returns the `application' function. If any arguments are given, + they are parsed according to the module documentation. + """ + for arg in argv: + if arg[0] == '.': + p = arg.index('=') + addext(arg[1:p], arg[p + 1:]) return application