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Copyright 2009 Josh Marshall
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.
Base RPC Handler for Tornado
This is a basic server implementation, designed for use within the
Tornado framework. The classes in this library should not be used
directly, but rather though the XML or JSON RPC implementations.
You can use the utility functions like 'private' and 'start_server'.
from tornado.web import RequestHandler
import tornado.web
import tornado.ioloop
import tornado.httpserver
import types
import traceback
from tornadorpc.utils import getcallargs
# Configuration element
class Config(object):
verbose = True
short_errors = True
config = Config()
class BaseRPCParser(object):
This class is responsible for managing the request, dispatch,
and response formatting of the system. It is tied into the
_RPC_ attribute of the BaseRPCHandler (or subclasses) and
populated as necessary throughout the request. Use the
.faults attribute to take advantage of the built-in error
content_type = 'text/plain'
def __init__(self, library, encode=None, decode=None):
# Attaches the RPC library and encode / decode functions.
self.library = library
if not encode:
encode = getattr(library, 'dumps')
if not decode:
decode = getattr(library, 'loads')
self.encode = encode
self.decode = decode
self.requests_in_progress = 0
self.responses = []
def faults(self):
# Grabs the fault tree on request
return Faults(self)
def run(self, handler, request_body):
This is the main loop -- it passes the request body to
the parse_request method, and then takes the resulting
method(s) and parameters and passes them to the appropriate
method on the parent Handler class, then parses the response
into text and returns it to the parent Handler to send back
to the client.
self.handler = handler
requests = self.parse_request(request_body)
return self.handler.result(self.faults.parse_error())
if type(requests) is not types.TupleType:
# SHOULD be the result of a fault call,
# according tothe parse_request spec below.
if type(requests) in types.StringTypes:
# Should be the response text of a fault
return requests
elif hasattr(requests, 'response'):
# Fault types should have a 'response' method
return requests.response()
elif hasattr(requests, 'faultCode'):
# XML-RPC fault types need to be properly dispatched. This
# should only happen if there was an error parsing the
# request above.
return self.handler.result(requests)
# No idea, hopefully the handler knows what it
# is doing.
return requests
self.handler._requests = len(requests)
for request in requests:
self.dispatch(request[0], request[1])
def dispatch(self, method_name, params):
This method walks the attribute tree in the method
and passes the parameters, either in positional or
keyword form, into the appropriate method on the
Handler class. Currently supports only positional
or keyword arguments, not mixed.
if method_name in dir(RequestHandler):
# Pre-existing, not an implemented attribute
return self.handler.result(self.faults.method_not_found())
method = self.handler
method_list = dir(method)
attr_tree = method_name.split('.')
for attr_name in attr_tree:
method = self.check_method(attr_name, method)
except AttributeError:
return self.handler.result(self.faults.method_not_found())
if not callable(method):
# Not callable, so not a method
return self.handler.result(self.faults.method_not_found())
if method_name.startswith('_') or \
('private' in dir(method) and method.private is True):
# No, no. That's private.
return self.handler.result(self.faults.method_not_found())
args = []
kwargs = {}
if type(params) is types.DictType:
# The parameters are keyword-based
kwargs = params
elif type(params) in (list, tuple):
# The parameters are positional
args = params
# Bad argument formatting?
return self.handler.result(self.faults.invalid_params())
# Validating call arguments
final_kwargs, extra_args = getcallargs(method, *args, **kwargs)
except TypeError:
return self.handler.result(self.faults.invalid_params())
response = method(*extra_args, **final_kwargs)
except Exception:
self.traceback(method_name, params)
return self.handler.result(self.faults.internal_error())
if 'async' in dir(method) and method.async:
# Asynchronous response -- the method should have called
# self.result(RESULT_VALUE)
if response != None:
# This should be deprecated to use self.result
message = "Async results should use 'self.result()'"
message += " Return result will be ignored."
# Synchronous result -- we call result manually.
return self.handler.result(response)
def response(self, handler):
This is the callback for a single finished dispatch.
Once all the dispatches have been run, it calls the
parser library to parse responses and then calls the
handler's asynch method.
handler._requests -= 1
if handler._requests > 0:
# We are finished with requests, send response
if handler._RPC_finished:
# We've already sent the response
raise Exception("Error trying to send response twice.")
handler._RPC_finished = True
responses = tuple(handler._results)
response_text = self.parse_responses(responses)
if type(response_text) not in types.StringTypes:
# Likely a fault, or something messed up
response_text = self.encode(response_text)
# Calling the asynch callback
def traceback(self, method_name='REQUEST', params=[]):
err_lines = traceback.format_exc().splitlines()
err_title = "ERROR IN %s" % method_name
if len(params) > 0:
err_title = '%s - (PARAMS: %s)' % (err_title, repr(params))
err_sep = ('-'*len(err_title))[:79]
err_lines = [err_sep, err_title, err_sep]+err_lines
if config.verbose == True:
if len(err_lines) >= 7 and config.short_errors:
# Minimum number of lines to see what happened
# Plus title and separators
print '\n'.join(err_lines[0:4]+err_lines[-3:])
print '\n'.join(err_lines)
# Log here
def parse_request(self, request_body):
Extend this on the implementing protocol. If it
should error out, return the output of the
'self.faults.fault_name' response. Otherwise,
it MUST return a TUPLE of TUPLE. Each entry
tuple must have the following structure:
('method_name', params)
...where params is a list or dictionary of
arguments (positional or keyword, respectively.)
So, the result should look something like
the following:
( ('add', [5,4]), ('add', {'x':5, 'y':4}) )
return ([], [])
def parse_responses(self, responses):
Extend this on the implementing protocol. It must
return a response that can be returned as output to
the client.
return self.encode(responses, methodresponse = True)
def check_method(self, attr_name, obj):
Just checks to see whether an attribute is private
(by the decorator or by a leading underscore) and
returns boolean result.
if attr_name.startswith('_'):
raise AttributeError('Private object or method.')
attr = getattr(obj, attr_name)
if 'private' in dir(attr) and attr.private == True:
raise AttributeError('Private object or method.')
return attr
class BaseRPCHandler(RequestHandler):
This is the base handler to be subclassed by the actual
implementations and by the end user.
_RPC_ = None
_results = None
_requests = 0
_RPC_finished = False
def post(self):
# Very simple -- dispatches request body to the parser
# and returns the output
self._results = []
request_body = self.request.body, request_body)
def result(self, result, *results):
""" Use this to return a result. """
if results:
results = [result,]+results
results = result
def on_result(self, response_text):
""" Asynchronous callback. """
self.set_header('Content-Type', self._RPC_.content_type)
class FaultMethod(object):
This is the 'dynamic' fault method so that the message can
be changed on request from the parser.faults call.
def __init__(self, fault, code, message):
self.fault = fault
self.code = code
self.message = message
def __call__(self, message=None):
if message:
self.message = message
return self.fault(self.code, self.message)
class Faults(object):
This holds the codes and messages for the RPC implementation.
It is attached (dynamically) to the Parser when called via the
parser.faults query, and returns a FaultMethod to be called so
that the message can be changed. If the 'dynamic' attribute is
not a key in the codes list, then it will error.
parser.fault.parse_error('Error parsing content.')
If no message is passed in, it will check the messages dictionary
for the same key as the codes dict. Otherwise, it just prettifies
the code 'key' from the codes dict.
codes = {
'parse_error': -32700,
'method_not_found': -32601,
'invalid_request': -32600,
'invalid_params': -32602,
'internal_error': -32603
messages = {}
def __init__(self, parser, fault=None):
self.library = parser.library
self.fault = fault
if not self.fault:
self.fault = getattr(self.library, 'Fault')
def __getattr__(self, attr):
message = 'Error'
if attr in self.messages.keys():
message = self.messages[attr]
message = ' '.join(map(str.capitalize, attr.split('_')))
fault = FaultMethod(self.fault,[attr], message)
return fault
Utility Functions
def private(func):
Use this to make a method private.
It is intended to be used as a decorator.
If you wish to make a method tree private, just
create and set the 'private' variable to True
on the tree object itself.
func.private = True
return func
def async(func):
Use this to make a method asynchronous
It is intended to be used as a decorator.
Make sure you call "self.result" on any
async method. Also, trees do not currently
support async methods.
func.async = True
return func
def start_server(handlers, route=r'/', port=8080):
This is just a friendly wrapper around the default
Tornado instantiation calls. It simplifies the imports
and setup calls you'd make otherwise.
start_server(handler_class, route=r'/', port=8181)
if type(handlers) not in (types.ListType, types.TupleType):
handler = handlers
handlers = [(route, handler),]
if route != '/RPC2':
# friendly addition for /RPC2 if it's the only one
handlers.append(('/RPC2', handler))
application = tornado.web.Application(handlers)
http_server = tornado.httpserver.HTTPServer(application)
loop_instance = tornado.ioloop.IOLoop.instance()
""" Setting the '_server' attribute if not set """
for (route, handler) in handlers:
server_attrib = setattr(handler, '_server', loop_instance)
except AttributeError:
handler._server = loop_instance
return loop_instance
The following is a test implementation which should work
for both the XMLRPC and the JSONRPC clients.
class TestMethodTree(object):
def power(self, x, y=2):
return pow(x, y)
def private(self):
# Shouldn't be called
return False
class TestRPCHandler(BaseRPCHandler):
_RPC_ = None
def add(self, x, y):
return x+y
def ping(self, x):
return x
def noargs(self):
return 'Works!'
tree = TestMethodTree()
def _private(self):
# Shouldn't be called
return False
def private(self):
# Also shouldn't be called
return False
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