4.5.3.1 Request Methods

add_common_vars( ): Calls the Apache ap_add_common_vars() function. After a call to this method, req.subprocess_env will contain a lot of CGI information.

add_handler( htype, handler[, dir])

Allows dynamic handler registration. htype is a string containing the name of any of the apache request (but not filter or connection) handler directives, e.g. "PythonHandler". handler is a string containing the name of the module and the handler function. Optional dir is a string containing the name of the directory to be added to the pythonpath. If no directory is specified, then, if there is already a handler of the same type specified, its directory is inherited, otherwise the directory of the presently executing handler is used. If there is a PythonPath directive in effect, then sys.path will be set exactly according to it (no directories added, the dir argument is ignored).

A handler added this way only persists throughout the life of the request. It is possible to register more handlers while inside the handler of the same type. One has to be careful as to not to create an infinite loop this way.

Dynamic handler registration is a useful technique that allows the code to dynamically decide what will happen next. A typical example might be a PythonAuthenHandler that will assign different PythonHandlers based on the authorization level, something like:

if manager:
    req.add_handler("PythonHandler", "menu::admin")
else:
    req.add_handler("PythonHandler", "menu::basic")

Note: If you pass this function an invalid handler, an exception will be generated at the time an attempt is made to find the handler.

allow_methods( methods[, reset]): Adds methods to the req.allowed_methods list. This list will be passed in Allowed: header if HTTP_METHOD_NOT_ALLOWED or HTTP_NOT_IMPLEMENTED is returned to the client. Note that Apache doesn't do anything to restrict the methods, this list is only used to construct the header. The actual method-restricting logic has to be provided in the handler code.
methods is a sequence of strings. If reset is 1, then the list of methods is first cleared.

document_root( ): Returns DocumentRoot setting.

get_basic_auth_pw( ): Returns a string containing the password when Basic authentication is used.

get_config( ): Returns a reference to the table object containing the mod_python configuration in effect for this request except for Python*Handler and PythonOption (The latter can be obtained via req.get_options(). The table has directives as keys, and their values, if any, as values.

get_remote_host( [type, str_is_ip])

This method is used to determine remote client's DNS name or IP number. The first call to this function may entail a DNS look up, but subsequent calls will use the cached result from the first call.

The optional type argument can specify the following:

apache.REMOTE_HOST Look up the DNS name. Return None if Apache directive HostNameLookups is off or the hostname cannot be determined.
apache.REMOTE_NAME (Default) Return the DNS name if possible, or the IP (as a string in dotted decimal notation) otherwise.
apache.REMOTE_NOLOOKUP Don't perform a DNS lookup, return an IP. Note: if a lookup was performed prior to this call, then the cached host name is returned.
apache.REMOTE_DOUBLE_REV Force a double-reverse lookup. On failure, return None.

If str_is_ip is None or unspecified, then the return value is a string representing the DNS name or IP address.

If the optional str_is_ip argument is not None, then the return value is an (address, str_is_ip) tuple, where str_is_ip is non-zero if address is an IP address string.

On failure, None is returned.

get_options( ): Returns a reference to the table object containing the options set by the PythonOption directives.

internal_redirect( new_uri)

Internally redirects the request to the new_uri. new_uri must be a string.

The httpd server handles internal redirection by creating a new request object and processing all request phases. Within an internal redirect, req.prev will contain a reference to a request object from which it was redirected.

log_error( message[, level])

An interface to the Apache ap_log_rerror function. message is a string with the error message, level is one of the following flags constants:

    APLOG_EMERG
    APLOG_ALERT
    APLOG_CRIT
    APLOG_ERR
    APLOG_WARNING
    APLOG_NOTICE
    APLOG_INFO
    APLOG_DEBUG
    APLOG_NOERRNO

If you need to write to log and do not have a reference to a request object, use the apache.log_error function.

meets_conditions( )

Calls the Apache ap_meets_conditions() function which returns a status code. If status is apache.OK, generate the content of the response normally. If not, simply return status. Note that req.headers_out should be set prior to calling this function. The same goes for req.status if the status differs from apache.OK.

Example:

...
r.headers_out['ETag'] = "1130794f-3774-4584-a4ea-0ab19e684268"
r.headers_out['Last-Modified'] = 'Wed, 23 Feb 2005 00:00:00 GMT'
r.headers_out['Expires'] = 'Mon, 18 Apr 2005 17:30:00 GMT'

status = r.meets_conditions()
if status != apache.OK:
  return status

... do expensive generation of the response content ...

requires( )

Returns a tuple of strings of arguments to require directive.

For example, with the following apache configuration:

AuthType Basic
require user joe
require valid-user

requires() would return ('user joe', 'valid-user').

read( [len])

Reads at most len bytes directly from the client, returning a string with the data read. If the len argument is negative or omitted, reads all data given by the client.

This function is affected by the Timeout Apache configuration directive. The read will be aborted and an IOError raised if the Timeout is reached while reading client data.

This function relies on the client providing the Content-length header. Absence of the Content-length header will be treated as if Content-length: 0 was supplied.

Incorrect Content-length may cause the function to try to read more data than available, which will make the function block until a Timeout is reached.

readline( [len])

Like read() but reads until end of line.

Note: In accordance with the HTTP specification, most clients will be terminating lines with "\r\n" rather than simply "\n".

readlines( [sizehint]): Reads all or up to sizehint bytes of lines using readline and returns a list of the lines read.

register_cleanup( callable[, data])

Registers a cleanup. Argument callable can be any callable object, the optional argument data can be any object (default is None). At the very end of the request, just before the actual request record is destroyed by Apache, callable will be called with one argument, data.

It is OK to pass the request object as data, but keep in mind that when the cleanup is executed, the request processing is already complete, so doing things like writing to the client is completely pointless.

If errors are encountered during cleanup processing, they should be in error log, but otherwise will not affect request processing in any way, which makes cleanup bugs sometimes hard to spot.

If the server is shut down before the cleanup had a chance to run, it's possible that it will not be executed.

sendfile( path[, offset, len])

Sends len bytes of file path directly to the client, starting at offset offset using the server's internal API. offset defaults to 0, and len defaults to -1 (send the entire file).

Returns the number of bytes sent, or raises an IOError exception on failure.

This function provides the most efficient way to send a file to the client.

write( string[, flush=1]): Writes string directly to the client, then flushes the buffer, unless flush is 0.

flush( ): Flushes the output buffer.

set_content_length( len): Sets the value of req.clength and the "Content-Length" header to len. Note that after the headers have been sent out (which happens just before the first byte of the body is written, i.e. first call to req.write()), calling the method is meaningless.