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Diffstat (limited to 'Lib/wsgiref/handlers.py')
| -rw-r--r-- | Lib/wsgiref/handlers.py | 492 |
1 files changed, 492 insertions, 0 deletions
diff --git a/Lib/wsgiref/handlers.py b/Lib/wsgiref/handlers.py new file mode 100644 index 0000000..52771a2 --- /dev/null +++ b/Lib/wsgiref/handlers.py @@ -0,0 +1,492 @@ +"""Base classes for server/gateway implementations""" + +from types import StringType +from util import FileWrapper, guess_scheme, is_hop_by_hop +from headers import Headers + +import sys, os, time + +__all__ = ['BaseHandler', 'SimpleHandler', 'BaseCGIHandler', 'CGIHandler'] + +try: + dict +except NameError: + def dict(items): + d = {} + for k,v in items: + d[k] = v + return d + +try: + True + False +except NameError: + True = not None + False = not True + + +# Weekday and month names for HTTP date/time formatting; always English! +_weekdayname = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"] +_monthname = [None, # Dummy so we can use 1-based month numbers + "Jan", "Feb", "Mar", "Apr", "May", "Jun", + "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"] + +def format_date_time(timestamp): + year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp) + return "%s, %02d %3s %4d %02d:%02d:%02d GMT" % ( + _weekdayname[wd], day, _monthname[month], year, hh, mm, ss + ) + + + +class BaseHandler: + """Manage the invocation of a WSGI application""" + + # Configuration parameters; can override per-subclass or per-instance + wsgi_version = (1,0) + wsgi_multithread = True + wsgi_multiprocess = True + wsgi_run_once = False + + origin_server = True # We are transmitting direct to client + http_version = "1.0" # Version that should be used for response + server_software = None # String name of server software, if any + + # os_environ is used to supply configuration from the OS environment: + # by default it's a copy of 'os.environ' as of import time, but you can + # override this in e.g. your __init__ method. + os_environ = dict(os.environ.items()) + + # Collaborator classes + wsgi_file_wrapper = FileWrapper # set to None to disable + headers_class = Headers # must be a Headers-like class + + # Error handling (also per-subclass or per-instance) + traceback_limit = None # Print entire traceback to self.get_stderr() + error_status = "500 Dude, this is whack!" + error_headers = [('Content-Type','text/plain')] + error_body = "A server error occurred. Please contact the administrator." + + # State variables (don't mess with these) + status = result = None + headers_sent = False + headers = None + bytes_sent = 0 + + + + + + + + + def run(self, application): + """Invoke the application""" + # Note to self: don't move the close()! Asynchronous servers shouldn't + # call close() from finish_response(), so if you close() anywhere but + # the double-error branch here, you'll break asynchronous servers by + # prematurely closing. Async servers must return from 'run()' without + # closing if there might still be output to iterate over. + try: + self.setup_environ() + self.result = application(self.environ, self.start_response) + self.finish_response() + except: + try: + self.handle_error() + except: + # If we get an error handling an error, just give up already! + self.close() + raise # ...and let the actual server figure it out. + + + def setup_environ(self): + """Set up the environment for one request""" + + env = self.environ = self.os_environ.copy() + self.add_cgi_vars() + + env['wsgi.input'] = self.get_stdin() + env['wsgi.errors'] = self.get_stderr() + env['wsgi.version'] = self.wsgi_version + env['wsgi.run_once'] = self.wsgi_run_once + env['wsgi.url_scheme'] = self.get_scheme() + env['wsgi.multithread'] = self.wsgi_multithread + env['wsgi.multiprocess'] = self.wsgi_multiprocess + + if self.wsgi_file_wrapper is not None: + env['wsgi.file_wrapper'] = self.wsgi_file_wrapper + + if self.origin_server and self.server_software: + env.setdefault('SERVER_SOFTWARE',self.server_software) + + + def finish_response(self): + """Send any iterable data, then close self and the iterable + + Subclasses intended for use in asynchronous servers will + want to redefine this method, such that it sets up callbacks + in the event loop to iterate over the data, and to call + 'self.close()' once the response is finished. + """ + if not self.result_is_file() or not self.sendfile(): + for data in self.result: + self.write(data) + self.finish_content() + self.close() + + + def get_scheme(self): + """Return the URL scheme being used""" + return guess_scheme(self.environ) + + + def set_content_length(self): + """Compute Content-Length or switch to chunked encoding if possible""" + try: + blocks = len(self.result) + except (TypeError,AttributeError,NotImplementedError): + pass + else: + if blocks==1: + self.headers['Content-Length'] = str(self.bytes_sent) + return + # XXX Try for chunked encoding if origin server and client is 1.1 + + + def cleanup_headers(self): + """Make any necessary header changes or defaults + + Subclasses can extend this to add other defaults. + """ + if not self.headers.has_key('Content-Length'): + self.set_content_length() + + def start_response(self, status, headers,exc_info=None): + """'start_response()' callable as specified by PEP 333""" + + if exc_info: + try: + if self.headers_sent: + # Re-raise original exception if headers sent + raise exc_info[0], exc_info[1], exc_info[2] + finally: + exc_info = None # avoid dangling circular ref + elif self.headers is not None: + raise AssertionError("Headers already set!") + + assert type(status) is StringType,"Status must be a string" + assert len(status)>=4,"Status must be at least 4 characters" + assert int(status[:3]),"Status message must begin w/3-digit code" + assert status[3]==" ", "Status message must have a space after code" + if __debug__: + for name,val in headers: + assert type(name) is StringType,"Header names must be strings" + assert type(val) is StringType,"Header values must be strings" + assert not is_hop_by_hop(name),"Hop-by-hop headers not allowed" + self.status = status + self.headers = self.headers_class(headers) + return self.write + + + def send_preamble(self): + """Transmit version/status/date/server, via self._write()""" + if self.origin_server: + if self.client_is_modern(): + self._write('HTTP/%s %s\r\n' % (self.http_version,self.status)) + if not self.headers.has_key('Date'): + self._write( + 'Date: %s\r\n' % format_date_time(time.time()) + ) + if self.server_software and not self.headers.has_key('Server'): + self._write('Server: %s\r\n' % self.server_software) + else: + self._write('Status: %s\r\n' % self.status) + + def write(self, data): + """'write()' callable as specified by PEP 333""" + + assert type(data) is StringType,"write() argument must be string" + + if not self.status: + raise AssertionError("write() before start_response()") + + elif not self.headers_sent: + # Before the first output, send the stored headers + self.bytes_sent = len(data) # make sure we know content-length + self.send_headers() + else: + self.bytes_sent += len(data) + + # XXX check Content-Length and truncate if too many bytes written? + self._write(data) + self._flush() + + + def sendfile(self): + """Platform-specific file transmission + + Override this method in subclasses to support platform-specific + file transmission. It is only called if the application's + return iterable ('self.result') is an instance of + 'self.wsgi_file_wrapper'. + + This method should return a true value if it was able to actually + transmit the wrapped file-like object using a platform-specific + approach. It should return a false value if normal iteration + should be used instead. An exception can be raised to indicate + that transmission was attempted, but failed. + + NOTE: this method should call 'self.send_headers()' if + 'self.headers_sent' is false and it is going to attempt direct + transmission of the file. + """ + return False # No platform-specific transmission by default + + + def finish_content(self): + """Ensure headers and content have both been sent""" + if not self.headers_sent: + self.headers['Content-Length'] = "0" + self.send_headers() + else: + pass # XXX check if content-length was too short? + + def close(self): + """Close the iterable (if needed) and reset all instance vars + + Subclasses may want to also drop the client connection. + """ + try: + if hasattr(self.result,'close'): + self.result.close() + finally: + self.result = self.headers = self.status = self.environ = None + self.bytes_sent = 0; self.headers_sent = False + + + def send_headers(self): + """Transmit headers to the client, via self._write()""" + self.cleanup_headers() + self.headers_sent = True + if not self.origin_server or self.client_is_modern(): + self.send_preamble() + self._write(str(self.headers)) + + + def result_is_file(self): + """True if 'self.result' is an instance of 'self.wsgi_file_wrapper'""" + wrapper = self.wsgi_file_wrapper + return wrapper is not None and isinstance(self.result,wrapper) + + + def client_is_modern(self): + """True if client can accept status and headers""" + return self.environ['SERVER_PROTOCOL'].upper() != 'HTTP/0.9' + + + def log_exception(self,exc_info): + """Log the 'exc_info' tuple in the server log + + Subclasses may override to retarget the output or change its format. + """ + try: + from traceback import print_exception + stderr = self.get_stderr() + print_exception( + exc_info[0], exc_info[1], exc_info[2], + self.traceback_limit, stderr + ) + stderr.flush() + finally: + exc_info = None + + def handle_error(self): + """Log current error, and send error output to client if possible""" + self.log_exception(sys.exc_info()) + if not self.headers_sent: + self.result = self.error_output(self.environ, self.start_response) + self.finish_response() + # XXX else: attempt advanced recovery techniques for HTML or text? + + def error_output(self, environ, start_response): + """WSGI mini-app to create error output + + By default, this just uses the 'error_status', 'error_headers', + and 'error_body' attributes to generate an output page. It can + be overridden in a subclass to dynamically generate diagnostics, + choose an appropriate message for the user's preferred language, etc. + + Note, however, that it's not recommended from a security perspective to + spit out diagnostics to any old user; ideally, you should have to do + something special to enable diagnostic output, which is why we don't + include any here! + """ + start_response(self.error_status,self.error_headers[:],sys.exc_info()) + return [self.error_body] + + + # Pure abstract methods; *must* be overridden in subclasses + + def _write(self,data): + """Override in subclass to buffer data for send to client + + It's okay if this method actually transmits the data; BaseHandler + just separates write and flush operations for greater efficiency + when the underlying system actually has such a distinction. + """ + raise NotImplementedError + + def _flush(self): + """Override in subclass to force sending of recent '_write()' calls + + It's okay if this method is a no-op (i.e., if '_write()' actually + sends the data. + """ + raise NotImplementedError + + def get_stdin(self): + """Override in subclass to return suitable 'wsgi.input'""" + raise NotImplementedError + + def get_stderr(self): + """Override in subclass to return suitable 'wsgi.errors'""" + raise NotImplementedError + + def add_cgi_vars(self): + """Override in subclass to insert CGI variables in 'self.environ'""" + raise NotImplementedError + + + + + + + + + + + +class SimpleHandler(BaseHandler): + """Handler that's just initialized with streams, environment, etc. + + This handler subclass is intended for synchronous HTTP/1.0 origin servers, + and handles sending the entire response output, given the correct inputs. + + Usage:: + + handler = SimpleHandler( + inp,out,err,env, multithread=False, multiprocess=True + ) + handler.run(app)""" + + def __init__(self,stdin,stdout,stderr,environ, + multithread=True, multiprocess=False + ): + self.stdin = stdin + self.stdout = stdout + self.stderr = stderr + self.base_env = environ + self.wsgi_multithread = multithread + self.wsgi_multiprocess = multiprocess + + def get_stdin(self): + return self.stdin + + def get_stderr(self): + return self.stderr + + def add_cgi_vars(self): + self.environ.update(self.base_env) + + def _write(self,data): + self.stdout.write(data) + self._write = self.stdout.write + + def _flush(self): + self.stdout.flush() + self._flush = self.stdout.flush + + +class BaseCGIHandler(SimpleHandler): + + """CGI-like systems using input/output/error streams and environ mapping + + Usage:: + + handler = BaseCGIHandler(inp,out,err,env) + handler.run(app) + + This handler class is useful for gateway protocols like ReadyExec and + FastCGI, that have usable input/output/error streams and an environment + mapping. It's also the base class for CGIHandler, which just uses + sys.stdin, os.environ, and so on. + + The constructor also takes keyword arguments 'multithread' and + 'multiprocess' (defaulting to 'True' and 'False' respectively) to control + the configuration sent to the application. It sets 'origin_server' to + False (to enable CGI-like output), and assumes that 'wsgi.run_once' is + False. + """ + + origin_server = False + + + + + + + + + + + + + + + + + + + +class CGIHandler(BaseCGIHandler): + + """CGI-based invocation via sys.stdin/stdout/stderr and os.environ + + Usage:: + + CGIHandler().run(app) + + The difference between this class and BaseCGIHandler is that it always + uses 'wsgi.run_once' of 'True', 'wsgi.multithread' of 'False', and + 'wsgi.multiprocess' of 'True'. It does not take any initialization + parameters, but always uses 'sys.stdin', 'os.environ', and friends. + + If you need to override any of these parameters, use BaseCGIHandler + instead. + """ + + wsgi_run_once = True + + def __init__(self): + BaseCGIHandler.__init__( + self, sys.stdin, sys.stdout, sys.stderr, dict(os.environ.items()), + multithread=False, multiprocess=True + ) + + + + + + + + + + + + + + + + + |