1 #!/usr/bin/env python

     2 #

     3 # Copyright 2007 Google Inc.

     4 #

     5 # Licensed under the Apache License, Version 2.0 (the "License");

     6 # you may not use this file except in compliance with the License.

     7 # You may obtain a copy of the License at

     8 #

     9 #     http://www.apache.org/licenses/LICENSE-2.0

    10 #

    11 # Unless required by applicable law or agreed to in writing, software

    12 # distributed under the License is distributed on an "AS IS" BASIS,

    13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

    14 # See the License for the specific language governing permissions and

    15 # limitations under the License.

    16 #

    17 

    18 """Makes API calls to various Google-provided services.

    19 

    20 Provides methods for making calls into Google Apphosting services and APIs

    21 from your application code. This code will only work properly from within

    22 the Google Apphosting environment.

    23 """

    24 

    25 

    26 import sys

    27 from google.net.proto import ProtocolBuffer

    28 from google.appengine import runtime

    29 from google.appengine.runtime import apiproxy_errors

    30 from google3.apphosting.runtime import _apphosting_runtime___python__apiproxy

    31 

    32 OK                =  0

    33 RPC_FAILED        =  1

    34 CALL_NOT_FOUND    =  2

    35 ARGUMENT_ERROR    =  3

    36 DEADLINE_EXCEEDED =  4

    37 CANCELLED         =  5

    38 APPLICATION_ERROR =  6

    39 OTHER_ERROR       =  7

    40 OVER_QUOTA        =  8

    41 REQUEST_TOO_LARGE =  9

    42 CAPABILITY_DISABLED = 10

    43 

    44 _ExceptionsMap = {

    45   RPC_FAILED:

    46   (apiproxy_errors.RPCFailedError,

    47    "The remote RPC to the application server failed for the call %s.%s()."),

    48   CALL_NOT_FOUND:

    49   (apiproxy_errors.CallNotFoundError,

    50    "The API package '%s' or call '%s()' was not found."),

    51   ARGUMENT_ERROR:

    52   (apiproxy_errors.ArgumentError,

    53    "An error occurred parsing (locally or remotely) the arguments to %s.%s()."),

    54   DEADLINE_EXCEEDED:

    55   (apiproxy_errors.DeadlineExceededError,

    56    "The API call %s.%s() took too long to respond and was cancelled."),

    57   CANCELLED:

    58   (apiproxy_errors.CancelledError,

    59    "The API call %s.%s() was explicitly cancelled."),

    60   OTHER_ERROR:

    61   (apiproxy_errors.Error,

    62    "An error occurred for the API request %s.%s()."),

    63   OVER_QUOTA:

    64   (apiproxy_errors.OverQuotaError,

    65   "The API call %s.%s() required more quota than is available."),

    66   REQUEST_TOO_LARGE:

    67   (apiproxy_errors.RequestTooLargeError,

    68   "The request to API call %s.%s() was too large."),

    69 

    70 

    71 

    72 

    73 

    74 

    75 }

    76 

    77 class RPC(object):

    78   """A RPC object, suitable for talking to remote services.

    79 

    80   Each instance of this object can be used only once, and should not be reused.

    81 

    82   Stores the data members and methods for making RPC calls via the APIProxy.

    83   """

    84 

    85   IDLE = 0

    86   RUNNING = 1

    87   FINISHING = 2

    88 

    89   def __init__(self, package=None, call=None, request=None, response=None,

    90                callback=None):

    91     """Constructor for the RPC object. All arguments are optional, and

    92     simply set members on the class. These data members will be

    93     overriden by values passed to MakeCall.

    94 

    95     Args:

    96       package: string, the package for the call

    97       call: string, the call within the package

    98       request: ProtocolMessage instance, appropriate for the arguments

    99       response: ProtocolMessage instance, appropriate for the response

   100       callback: callable, called when call is complete

   101     """

   102     self.__exception = None

   103     self.__traceback = None

   104     self.__result_dict = {}

   105     self.__state = RPC.IDLE

   106 

   107     self.package = package

   108     self.call = call

   109     self.request = request

   110     self.response = response

   111     self.callback = callback

   112 

   113 

   114   def MakeCall(self, package=None, call=None, request=None, response=None,

   115                callback=None):

   116     """Makes an asynchronous (i.e. non-blocking) API call within the

   117     specified package for the specified call method. request and response must

   118     be the appropriately typed ProtocolBuffers for the API call.

   119     callback, if provided, will be called when the request completes

   120     successfully or when an error occurs.  If an error has ocurred, the

   121     exception() method on this class will return the error, which can be

   122     accessed from the callback.

   123 

   124     Args:

   125       Same as constructor; see __init__.

   126 

   127     Raises:

   128       TypeError or AssertionError if an argument is of an invalid type.

   129       AssertionError or RuntimeError is an RPC is already in use.

   130     """

   131     self.callback = callback or self.callback

   132     self.package = package or self.package

   133     self.call = call or self.call

   134     self.request = request or self.request

   135     self.response = response or self.response

   136 

   137     assert self.__state is RPC.IDLE, ("RPC for %s.%s has already been started" %

   138                                       (self.package, self.call))

   139     assert self.callback is None or callable(self.callback)

   140     assert isinstance(self.request, ProtocolBuffer.ProtocolMessage)

   141     assert isinstance(self.response, ProtocolBuffer.ProtocolMessage)

   142 

   143     e = ProtocolBuffer.Encoder()

   144     self.request.Output(e)

   145 

   146     self.__state = RPC.RUNNING

   147     _apphosting_runtime___python__apiproxy.MakeCall(

   148         self.package, self.call, e.buffer(), self.__result_dict,

   149         self.__MakeCallDone, self)

   150 

   151   def Wait(self):

   152     """Waits on the API call associated with this RPC. The callback,

   153     if provided, will be executed before Wait() returns. If this RPC

   154     is already complete, or if the RPC was never started, this

   155     function will return immediately.

   156 

   157     Raises:

   158       InterruptedError if a callback throws an uncaught exception.

   159     """

   160     try:

   161       rpc_completed = _apphosting_runtime___python__apiproxy.Wait(self)

   162     except runtime.DeadlineExceededError:

   163       raise

   164     except apiproxy_errors.InterruptedError:

   165       raise

   166     except:

   167       exc_class, exc, tb = sys.exc_info()

   168       if (isinstance(exc, SystemError) and

   169           exc.args == ('uncaught RPC exception',)):

   170         raise

   171       rpc = None

   172       if hasattr(exc, "_appengine_apiproxy_rpc"):

   173         rpc = exc._appengine_apiproxy_rpc

   174       new_exc = apiproxy_errors.InterruptedError(exc, rpc)

   175       raise new_exc.__class__, new_exc, tb

   176 

   177     assert rpc_completed, ("RPC for %s.%s was not completed, and no other " +

   178                            "exception was raised " % (self.package, self.call))

   179 

   180   def CheckSuccess(self):

   181     """If there was an exception, raise it now.

   182 

   183     Raises:

   184       Exception of the API call or the callback, if any.

   185     """

   186     if self.exception and self.__traceback:

   187       raise self.exception.__class__, self.exception, self.__traceback

   188     if self.exception:

   189       raise self.exception

   190 

   191   @property

   192   def exception(self):

   193     return self.__exception

   194 

   195   @property

   196   def state(self):

   197     return self.__state

   198 

   199   def __MakeCallDone(self):

   200     self.__state = RPC.FINISHING

   201     if self.__result_dict['error'] == APPLICATION_ERROR:

   202       self.__exception = apiproxy_errors.ApplicationError(

   203           self.__result_dict['application_error'],

   204           self.__result_dict['error_detail'])

   205     elif self.__result_dict['error'] == CAPABILITY_DISABLED:

   206       if self.__result_dict['error_detail']:

   207         self.__exception = apiproxy_errors.CapabilityDisabledError(

   208             self.__result_dict['error_detail'])

   209       else:

   210         self.__exception = apiproxy_errors.CapabilityDisabledError(

   211             "The API call %s.%s() is temporarily unavailable." % (

   212             self.package, self.call))

   213     elif _ExceptionsMap.has_key(self.__result_dict['error']):

   214       exception_entry = _ExceptionsMap[self.__result_dict['error']]

   215       self.__exception = exception_entry[0](

   216           exception_entry[1] % (self.package, self.call))

   217     else:

   218       try:

   219         self.response.ParseFromString(self.__result_dict['result_string'])

   220       except Exception, e:

   221         self.__exception = e

   222     if self.callback:

   223       try:

   224         self.callback()

   225       except:

   226         exc_class, self.__exception, self.__traceback = sys.exc_info()

   227         self.__exception._appengine_apiproxy_rpc = self

   228         raise

   229 

   230 

   231 def MakeSyncCall(package, call, request, response):

   232   """Makes a synchronous (i.e. blocking) API call within the specified

   233   package for the specified call method. request and response must be the

   234   appropriately typed ProtocolBuffers for the API call. An exception is

   235   thrown if an error occurs when communicating with the system.

   236 

   237   Args:

   238     See MakeCall above.

   239 

   240   Raises:

   241     See CheckSuccess() above.

   242   """

   243   rpc = RPC()

   244   rpc.MakeCall(package, call, request, response)

   245   rpc.Wait()

   246   rpc.CheckSuccess()