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+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.
+# http://code.google.com/p/protobuf/
+#
+# 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
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Declares the RPC service interfaces.
+
+This module declares the abstract interfaces underlying proto2 RPC
+services. These are intented to be independent of any particular RPC
+implementation, so that proto2 services can be used on top of a variety
+of implementations.
+"""
+
+__author__ = 'petar@google.com (Petar Petrov)'
+
+
+class Service(object):
+
+ """Abstract base interface for protocol-buffer-based RPC services.
+
+ Services themselves are abstract classes (implemented either by servers or as
+ stubs), but they subclass this base interface. The methods of this
+ interface can be used to call the methods of the service without knowing
+ its exact type at compile time (analogous to the Message interface).
+ """
+
+ def GetDescriptor(self):
+ """Retrieves this service's descriptor."""
+ raise NotImplementedError
+
+ def CallMethod(self, method_descriptor, rpc_controller,
+ request, done):
+ """Calls a method of the service specified by method_descriptor.
+
+ Preconditions:
+ * method_descriptor.service == GetDescriptor
+ * request is of the exact same classes as returned by
+ GetRequestClass(method).
+ * After the call has started, the request must not be modified.
+ * "rpc_controller" is of the correct type for the RPC implementation being
+ used by this Service. For stubs, the "correct type" depends on the
+ RpcChannel which the stub is using.
+
+ Postconditions:
+ * "done" will be called when the method is complete. This may be
+ before CallMethod() returns or it may be at some point in the future.
+ """
+ raise NotImplementedError
+
+ def GetRequestClass(self, method_descriptor):
+ """Returns the class of the request message for the specified method.
+
+ CallMethod() requires that the request is of a particular subclass of
+ Message. GetRequestClass() gets the default instance of this required
+ type.
+
+ Example:
+ method = service.GetDescriptor().FindMethodByName("Foo")
+ request = stub.GetRequestClass(method)()
+ request.ParseFromString(input)
+ service.CallMethod(method, request, callback)
+ """
+ raise NotImplementedError
+
+ def GetResponseClass(self, method_descriptor):
+ """Returns the class of the response message for the specified method.
+
+ This method isn't really needed, as the RpcChannel's CallMethod constructs
+ the response protocol message. It's provided anyway in case it is useful
+ for the caller to know the response type in advance.
+ """
+ raise NotImplementedError
+
+
+class RpcController(object):
+
+ """Abstract interface for an RPC channel.
+
+ An RpcChannel represents a communication line to a service which can be used
+ to call that service's methods. The service may be running on another
+ machine. Normally, you should not use an RpcChannel directly, but instead
+ construct a stub {@link Service} wrapping it. Example:
+
+ Example:
+ RpcChannel channel = rpcImpl.Channel("remotehost.example.com:1234")
+ RpcController controller = rpcImpl.Controller()
+ MyService service = MyService_Stub(channel)
+ service.MyMethod(controller, request, callback)
+ """
+
+ # Client-side methods below
+
+ def Reset(self):
+ """Resets the RpcController to its initial state.
+
+ After the RpcController has been reset, it may be reused in
+ a new call. Must not be called while an RPC is in progress.
+ """
+ raise NotImplementedError
+
+ def Failed(self):
+ """Returns true if the call failed.
+
+ After a call has finished, returns true if the call failed. The possible
+ reasons for failure depend on the RPC implementation. Failed() must not
+ be called before a call has finished. If Failed() returns true, the
+ contents of the response message are undefined.
+ """
+ raise NotImplementedError
+
+ def ErrorText(self):
+ """If Failed is true, returns a human-readable description of the error."""
+ raise NotImplementedError
+
+ def StartCancel(self):
+ """Initiate cancellation.
+
+ Advises the RPC system that the caller desires that the RPC call be
+ canceled. The RPC system may cancel it immediately, may wait awhile and
+ then cancel it, or may not even cancel the call at all. If the call is
+ canceled, the "done" callback will still be called and the RpcController
+ will indicate that the call failed at that time.
+ """
+ raise NotImplementedError
+
+ # Server-side methods below
+
+ def SetFailed(self, reason):
+ """Sets a failure reason.
+
+ Causes Failed() to return true on the client side. "reason" will be
+ incorporated into the message returned by ErrorText(). If you find
+ you need to return machine-readable information about failures, you
+ should incorporate it into your response protocol buffer and should
+ NOT call SetFailed().
+ """
+ raise NotImplementedError
+
+ def IsCanceled(self):
+ """Checks if the client cancelled the RPC.
+
+ If true, indicates that the client canceled the RPC, so the server may
+ as well give up on replying to it. The server should still call the
+ final "done" callback.
+ """
+ raise NotImplementedError
+
+ def NotifyOnCancel(self, callback):
+ """Sets a callback to invoke on cancel.
+
+ Asks that the given callback be called when the RPC is canceled. The
+ callback will always be called exactly once. If the RPC completes without
+ being canceled, the callback will be called after completion. If the RPC
+ has already been canceled when NotifyOnCancel() is called, the callback
+ will be called immediately.
+
+ NotifyOnCancel() must be called no more than once per request.
+ """
+ raise NotImplementedError
+
+
+class RpcChannel(object):
+
+ """An RpcController mediates a single method call.
+
+ The primary purpose of the controller is to provide a way to manipulate
+ settings specific to the RPC implementation and to find out about RPC-level
+ errors. The methods provided by the RpcController interface are intended
+ to be a "least common denominator" set of features which we expect all
+ implementations to support. Specific implementations may provide more
+ advanced features (e.g. deadline propagation).
+ """
+
+ def CallMethod(self, method_descriptor, rpc_controller,
+ request, response_class, done):
+ """Calls the method identified by the descriptor.
+
+ Call the given method of the remote service. The signature of this
+ procedure looks the same as Service.CallMethod(), but the requirements
+ are less strict in one important way: the request object doesn't have to
+ be of any specific class as long as its descriptor is method.input_type.
+ """
+ raise NotImplementedError