Source code for google.appengine.api.apiproxy_rpc

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
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# 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
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#     http://www.apache.org/licenses/LICENSE-2.0
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"""Base class for implementing RPC of API proxy stubs."""










import sys


[docs]class RPC(object): """Base class for implementing RPC of API proxy stubs. To implement a RPC to make real asynchronous API call: - Extend this class. - Override _MakeCallImpl and/or _WaitImpl to do a real asynchronous call. """ IDLE = 0 RUNNING = 1 FINISHING = 2 def __init__(self, package=None, call=None, request=None, response=None, callback=None, deadline=None, stub=None): """Constructor for the RPC object. All arguments are optional, and simply set members on the class. These data members will be overriden by values passed to MakeCall. Args: package: string, the package for the call call: string, the call within the package request: ProtocolMessage instance, appropriate for the arguments response: ProtocolMessage instance, appropriate for the response callback: callable, called when call is complete deadline: A double specifying the deadline for this call as the number of seconds from the current time. Ignored if non-positive. stub: APIProxyStub instance, used in default _WaitImpl to do real call """ self._exception = None self._state = RPC.IDLE self._traceback = None self.package = package self.call = call self.request = request self.response = response self.callback = callback self.deadline = deadline self.stub = stub self.cpu_usage_mcycles = 0
[docs] def Clone(self): """Make a shallow copy of this instances attributes, excluding methods. This is usually used when an RPC has been specified with some configuration options and is being used as a template for multiple RPCs outside of a developer's easy control. """ if self.state != RPC.IDLE: raise AssertionError('Cannot clone a call already in progress') clone = self.__class__() for k, v in self.__dict__.iteritems(): setattr(clone, k, v) return clone
[docs] def MakeCall(self, package=None, call=None, request=None, response=None, callback=None, deadline=None): """Makes an asynchronous (i.e. non-blocking) API call within the specified package for the specified call method. It will call the _MakeRealCall to do the real job. Args: Same as constructor; see __init__. Raises: TypeError or AssertionError if an argument is of an invalid type. AssertionError or RuntimeError is an RPC is already in use. """ self.callback = callback or self.callback self.package = package or self.package self.call = call or self.call self.request = request or self.request self.response = response or self.response self.deadline = deadline or self.deadline assert self._state is RPC.IDLE, ('RPC for %s.%s has already been started' % (self.package, self.call)) assert self.callback is None or callable(self.callback) self._MakeCallImpl()
[docs] def Wait(self): """Waits on the API call associated with this RPC.""" rpc_completed = self._WaitImpl() assert rpc_completed, ('RPC for %s.%s was not completed, and no other ' 'exception was raised ' % (self.package, self.call))
[docs] def CheckSuccess(self): """If there was an exception, raise it now. Raises: Exception of the API call or the callback, if any. """ if self.exception and self._traceback: raise self.exception.__class__, self.exception, self._traceback elif self.exception: raise self.exception
@property def exception(self): return self._exception @property def state(self): return self._state def _MakeCallImpl(self): """Override this method to implement a real asynchronous call rpc.""" self._state = RPC.RUNNING def _WaitImpl(self): """Override this method to implement a real asynchronous call rpc. Returns: True if the async call was completed successfully. """ try: try: self.stub.MakeSyncCall(self.package, self.call, self.request, self.response) except Exception: _, self._exception, self._traceback = sys.exc_info() finally: self._state = RPC.FINISHING self._Callback() return True def _Callback(self): if self.callback: try: self.callback() except: _, self._exception, self._traceback = sys.exc_info() self._exception._appengine_apiproxy_rpc = self raise

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