// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Author: kenton@google.com (Kenton Varda)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// DEPRECATED: 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. Starting with version 2.3.0, RPC implementations should
// not try to build on these, but should instead provide code generator plugins
// which generate code specific to the particular RPC implementation. This way
// the generated code can be more appropriate for the implementation in use
// and can avoid unnecessary layers of indirection.
//
//
// When you use the protocol compiler to compile a service definition, it
// generates two classes: An abstract interface for the service (with
// methods matching the service definition) and a "stub" implementation.
// A stub is just a type-safe wrapper around an RpcChannel which emulates a
// local implementation of the service.
//
// For example, the service definition:
// service MyService {
// rpc Foo(MyRequest) returns(MyResponse);
// }
// will generate abstract interface "MyService" and class "MyService::Stub".
// You could implement a MyService as follows:
// class MyServiceImpl : public MyService {
// public:
// MyServiceImpl() {}
// ~MyServiceImpl() {}
//
// // implements MyService ---------------------------------------
//
// void Foo(google::protobuf::RpcController* controller,
// const MyRequest* request,
// MyResponse* response,
// Closure* done) {
// // ... read request and fill in response ...
// done->Run();
// }
// };
// You would then register an instance of MyServiceImpl with your RPC server
// implementation. (How to do that depends on the implementation.)
//
// To call a remote MyServiceImpl, first you need an RpcChannel connected to it.
// How to construct a channel depends, again, on your RPC implementation.
// Here we use a hypothentical "MyRpcChannel" as an example:
// MyRpcChannel channel("rpc:hostname:1234/myservice");
// MyRpcController controller;
// MyServiceImpl::Stub stub(&channel);
// FooRequest request;
// FooRespnose response;
//
// // ... fill in request ...
//
// stub.Foo(&controller, request, &response, NewCallback(HandleResponse));
//
// On Thread-Safety:
//
// Different RPC implementations may make different guarantees about what
// threads they may run callbacks on, and what threads the application is
// allowed to use to call the RPC system. Portable software should be ready
// for callbacks to be called on any thread, but should not try to call the
// RPC system from any thread except for the ones on which it received the
// callbacks. Realistically, though, simple software will probably want to
// use a single-threaded RPC system while high-end software will want to
// use multiple threads. RPC implementations should provide multiple
// choices.
#ifndef GOOGLE_PROTOBUF_SERVICE_H__
#define GOOGLE_PROTOBUF_SERVICE_H__
#include <string>
#include <google/protobuf/stubs/common.h>
namespace google {
namespace protobuf {
// Defined in this file.
class Service;
class RpcController;
class RpcChannel;
// Defined in other files.
class Descriptor; // descriptor.h
class ServiceDescriptor; // descriptor.h
class MethodDescriptor; // descriptor.h
class Message; // message.h
// Abstract base interface for protocol-buffer-based RPC services. Services
// themselves are abstract interfaces (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 Reflection).
class LIBPROTOBUF_EXPORT Service {
public:
inline Service() {}
virtual ~Service();
// When constructing a stub, you may pass STUB_OWNS_CHANNEL as the second
// parameter to the constructor to tell it to delete its RpcChannel when
// destroyed.
enum ChannelOwnership {
STUB_OWNS_CHANNEL,
STUB_DOESNT_OWN_CHANNEL
};
// Get the ServiceDescriptor describing this service and its methods.
virtual const ServiceDescriptor* GetDescriptor() = 0;
// Call a method of the service specified by MethodDescriptor. This is
// normally implemented as a simple switch() that calls the standard
// definitions of the service's methods.
//
// Preconditions:
// * method->service() == GetDescriptor()
// * request and response are of the exact same classes as the objects
// returned by GetRequestPrototype(method) and
// GetResponsePrototype(method).
// * After the call has started, the request must not be modified and the
// response must not be accessed at all until "done" is called.
// * "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. Server-side Service
// implementations are expected to accept whatever type of RpcController
// the server-side RPC implementation uses.
//
// 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.
// * If the RPC succeeded, "response" contains the response returned by
// the server.
// * If the RPC failed, "response"'s contents are undefined. The
// RpcController can be queried to determine if an error occurred and
// possibly to get more information about the error.
virtual void CallMethod(const MethodDescriptor* method,
RpcController* controller,
const Message* request,
Message* response,
Closure* done) = 0;
// CallMethod() requires that the request and response passed in are of a
// particular subclass of Message. GetRequestPrototype() and
// GetResponsePrototype() get the default instances of these required types.
// You can then call Message::New() on these instances to construct mutable
// objects which you can then pass to CallMethod().
//
// Example:
// const MethodDescriptor* method =
// service->GetDescriptor()->FindMethodByName("Foo");
// Message* request = stub->GetRequestPrototype (method)->New();
// Message* response = stub->GetResponsePrototype(method)->New();
// request->ParseFromString(input);
// service->CallMethod(method, *request, response, callback);
virtual const Message& GetRequestPrototype(
const MethodDescriptor* method) const = 0;
virtual const Message& GetResponsePrototype(
const MethodDescriptor* method) const = 0;
private:
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Service);
};
// 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).
class LIBPROTOBUF_EXPORT RpcController {
public:
inline RpcController() {}
virtual ~RpcController();
// Client-side methods ---------------------------------------------
// These calls may be made from the client side only. Their results
// are undefined on the server side (may crash).
// Resets the RpcController to its initial state so that it may be reused in
// a new call. Must not be called while an RPC is in progress.
virtual void Reset() = 0;
// 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.
virtual bool Failed() const = 0;
// If Failed() is true, returns a human-readable description of the error.
virtual string ErrorText() const = 0;
// 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.
virtual void StartCancel() = 0;
// Server-side methods ---------------------------------------------
// These calls may be made from the server side only. Their results
// are undefined on the client side (may crash).
// 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().
virtual void SetFailed(const string& reason) = 0;
// 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.
virtual bool IsCanceled() const = 0;
// 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.
virtual void NotifyOnCancel(Closure* callback) = 0;
private:
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcController);
};
// 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 call an RpcChannel directly, but instead construct a stub Service
// wrapping it. Example:
// RpcChannel* channel = new MyRpcChannel("remotehost.example.com:1234");
// MyService* service = new MyService::Stub(channel);
// service->MyMethod(request, &response, callback);
class LIBPROTOBUF_EXPORT RpcChannel {
public:
inline RpcChannel() {}
virtual ~RpcChannel();
// 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 and response objects
// need not be of any specific class as long as their descriptors are
// method->input_type() and method->output_type().
virtual void CallMethod(const MethodDescriptor* method,
RpcController* controller,
const Message* request,
Message* response,
Closure* done) = 0;
private:
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcChannel);
};
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_SERVICE_H__