1// Protocol Buffers - Google's data interchange format 2// Copyright 2008 Google Inc. All rights reserved. 3// http://code.google.com/p/protobuf/ 4// 5// Redistribution and use in source and binary forms, with or without 6// modification, are permitted provided that the following conditions are 7// met: 8// 9// * Redistributions of source code must retain the above copyright 10// notice, this list of conditions and the following disclaimer. 11// * Redistributions in binary form must reproduce the above 12// copyright notice, this list of conditions and the following disclaimer 13// in the documentation and/or other materials provided with the 14// distribution. 15// * Neither the name of Google Inc. nor the names of its 16// contributors may be used to endorse or promote products derived from 17// this software without specific prior written permission. 18// 19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31// Author: kenton@google.com (Kenton Varda) 32// Based on original Protocol Buffers design by 33// Sanjay Ghemawat, Jeff Dean, and others. 34// 35// DEPRECATED: This module declares the abstract interfaces underlying proto2 36// RPC services. These are intented to be independent of any particular RPC 37// implementation, so that proto2 services can be used on top of a variety 38// of implementations. Starting with version 2.3.0, RPC implementations should 39// not try to build on these, but should instead provide code generator plugins 40// which generate code specific to the particular RPC implementation. This way 41// the generated code can be more appropriate for the implementation in use 42// and can avoid unnecessary layers of indirection. 43// 44// 45// When you use the protocol compiler to compile a service definition, it 46// generates two classes: An abstract interface for the service (with 47// methods matching the service definition) and a "stub" implementation. 48// A stub is just a type-safe wrapper around an RpcChannel which emulates a 49// local implementation of the service. 50// 51// For example, the service definition: 52// service MyService { 53// rpc Foo(MyRequest) returns(MyResponse); 54// } 55// will generate abstract interface "MyService" and class "MyService::Stub". 56// You could implement a MyService as follows: 57// class MyServiceImpl : public MyService { 58// public: 59// MyServiceImpl() {} 60// ~MyServiceImpl() {} 61// 62// // implements MyService --------------------------------------- 63// 64// void Foo(google::protobuf::RpcController* controller, 65// const MyRequest* request, 66// MyResponse* response, 67// Closure* done) { 68// // ... read request and fill in response ... 69// done->Run(); 70// } 71// }; 72// You would then register an instance of MyServiceImpl with your RPC server 73// implementation. (How to do that depends on the implementation.) 74// 75// To call a remote MyServiceImpl, first you need an RpcChannel connected to it. 76// How to construct a channel depends, again, on your RPC implementation. 77// Here we use a hypothentical "MyRpcChannel" as an example: 78// MyRpcChannel channel("rpc:hostname:1234/myservice"); 79// MyRpcController controller; 80// MyServiceImpl::Stub stub(&channel); 81// FooRequest request; 82// FooRespnose response; 83// 84// // ... fill in request ... 85// 86// stub.Foo(&controller, request, &response, NewCallback(HandleResponse)); 87// 88// On Thread-Safety: 89// 90// Different RPC implementations may make different guarantees about what 91// threads they may run callbacks on, and what threads the application is 92// allowed to use to call the RPC system. Portable software should be ready 93// for callbacks to be called on any thread, but should not try to call the 94// RPC system from any thread except for the ones on which it received the 95// callbacks. Realistically, though, simple software will probably want to 96// use a single-threaded RPC system while high-end software will want to 97// use multiple threads. RPC implementations should provide multiple 98// choices. 99 100#ifndef GOOGLE_PROTOBUF_SERVICE_H__ 101#define GOOGLE_PROTOBUF_SERVICE_H__ 102 103#include <string> 104#include <google/protobuf/stubs/common.h> 105 106namespace google { 107namespace protobuf { 108 109// Defined in this file. 110class Service; 111class RpcController; 112class RpcChannel; 113 114// Defined in other files. 115class Descriptor; // descriptor.h 116class ServiceDescriptor; // descriptor.h 117class MethodDescriptor; // descriptor.h 118class Message; // message.h 119 120// Abstract base interface for protocol-buffer-based RPC services. Services 121// themselves are abstract interfaces (implemented either by servers or as 122// stubs), but they subclass this base interface. The methods of this 123// interface can be used to call the methods of the Service without knowing 124// its exact type at compile time (analogous to Reflection). 125class LIBPROTOBUF_EXPORT Service { 126 public: 127 inline Service() {} 128 virtual ~Service(); 129 130 // When constructing a stub, you may pass STUB_OWNS_CHANNEL as the second 131 // parameter to the constructor to tell it to delete its RpcChannel when 132 // destroyed. 133 enum ChannelOwnership { 134 STUB_OWNS_CHANNEL, 135 STUB_DOESNT_OWN_CHANNEL 136 }; 137 138 // Get the ServiceDescriptor describing this service and its methods. 139 virtual const ServiceDescriptor* GetDescriptor() = 0; 140 141 // Call a method of the service specified by MethodDescriptor. This is 142 // normally implemented as a simple switch() that calls the standard 143 // definitions of the service's methods. 144 // 145 // Preconditions: 146 // * method->service() == GetDescriptor() 147 // * request and response are of the exact same classes as the objects 148 // returned by GetRequestPrototype(method) and 149 // GetResponsePrototype(method). 150 // * After the call has started, the request must not be modified and the 151 // response must not be accessed at all until "done" is called. 152 // * "controller" is of the correct type for the RPC implementation being 153 // used by this Service. For stubs, the "correct type" depends on the 154 // RpcChannel which the stub is using. Server-side Service 155 // implementations are expected to accept whatever type of RpcController 156 // the server-side RPC implementation uses. 157 // 158 // Postconditions: 159 // * "done" will be called when the method is complete. This may be 160 // before CallMethod() returns or it may be at some point in the future. 161 // * If the RPC succeeded, "response" contains the response returned by 162 // the server. 163 // * If the RPC failed, "response"'s contents are undefined. The 164 // RpcController can be queried to determine if an error occurred and 165 // possibly to get more information about the error. 166 virtual void CallMethod(const MethodDescriptor* method, 167 RpcController* controller, 168 const Message* request, 169 Message* response, 170 Closure* done) = 0; 171 172 // CallMethod() requires that the request and response passed in are of a 173 // particular subclass of Message. GetRequestPrototype() and 174 // GetResponsePrototype() get the default instances of these required types. 175 // You can then call Message::New() on these instances to construct mutable 176 // objects which you can then pass to CallMethod(). 177 // 178 // Example: 179 // const MethodDescriptor* method = 180 // service->GetDescriptor()->FindMethodByName("Foo"); 181 // Message* request = stub->GetRequestPrototype (method)->New(); 182 // Message* response = stub->GetResponsePrototype(method)->New(); 183 // request->ParseFromString(input); 184 // service->CallMethod(method, *request, response, callback); 185 virtual const Message& GetRequestPrototype( 186 const MethodDescriptor* method) const = 0; 187 virtual const Message& GetResponsePrototype( 188 const MethodDescriptor* method) const = 0; 189 190 private: 191 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Service); 192}; 193 194// An RpcController mediates a single method call. The primary purpose of 195// the controller is to provide a way to manipulate settings specific to the 196// RPC implementation and to find out about RPC-level errors. 197// 198// The methods provided by the RpcController interface are intended to be a 199// "least common denominator" set of features which we expect all 200// implementations to support. Specific implementations may provide more 201// advanced features (e.g. deadline propagation). 202class LIBPROTOBUF_EXPORT RpcController { 203 public: 204 inline RpcController() {} 205 virtual ~RpcController(); 206 207 // Client-side methods --------------------------------------------- 208 // These calls may be made from the client side only. Their results 209 // are undefined on the server side (may crash). 210 211 // Resets the RpcController to its initial state so that it may be reused in 212 // a new call. Must not be called while an RPC is in progress. 213 virtual void Reset() = 0; 214 215 // After a call has finished, returns true if the call failed. The possible 216 // reasons for failure depend on the RPC implementation. Failed() must not 217 // be called before a call has finished. If Failed() returns true, the 218 // contents of the response message are undefined. 219 virtual bool Failed() const = 0; 220 221 // If Failed() is true, returns a human-readable description of the error. 222 virtual string ErrorText() const = 0; 223 224 // Advises the RPC system that the caller desires that the RPC call be 225 // canceled. The RPC system may cancel it immediately, may wait awhile and 226 // then cancel it, or may not even cancel the call at all. If the call is 227 // canceled, the "done" callback will still be called and the RpcController 228 // will indicate that the call failed at that time. 229 virtual void StartCancel() = 0; 230 231 // Server-side methods --------------------------------------------- 232 // These calls may be made from the server side only. Their results 233 // are undefined on the client side (may crash). 234 235 // Causes Failed() to return true on the client side. "reason" will be 236 // incorporated into the message returned by ErrorText(). If you find 237 // you need to return machine-readable information about failures, you 238 // should incorporate it into your response protocol buffer and should 239 // NOT call SetFailed(). 240 virtual void SetFailed(const string& reason) = 0; 241 242 // If true, indicates that the client canceled the RPC, so the server may 243 // as well give up on replying to it. The server should still call the 244 // final "done" callback. 245 virtual bool IsCanceled() const = 0; 246 247 // Asks that the given callback be called when the RPC is canceled. The 248 // callback will always be called exactly once. If the RPC completes without 249 // being canceled, the callback will be called after completion. If the RPC 250 // has already been canceled when NotifyOnCancel() is called, the callback 251 // will be called immediately. 252 // 253 // NotifyOnCancel() must be called no more than once per request. 254 virtual void NotifyOnCancel(Closure* callback) = 0; 255 256 private: 257 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcController); 258}; 259 260// Abstract interface for an RPC channel. An RpcChannel represents a 261// communication line to a Service which can be used to call that Service's 262// methods. The Service may be running on another machine. Normally, you 263// should not call an RpcChannel directly, but instead construct a stub Service 264// wrapping it. Example: 265// RpcChannel* channel = new MyRpcChannel("remotehost.example.com:1234"); 266// MyService* service = new MyService::Stub(channel); 267// service->MyMethod(request, &response, callback); 268class LIBPROTOBUF_EXPORT RpcChannel { 269 public: 270 inline RpcChannel() {} 271 virtual ~RpcChannel(); 272 273 // Call the given method of the remote service. The signature of this 274 // procedure looks the same as Service::CallMethod(), but the requirements 275 // are less strict in one important way: the request and response objects 276 // need not be of any specific class as long as their descriptors are 277 // method->input_type() and method->output_type(). 278 virtual void CallMethod(const MethodDescriptor* method, 279 RpcController* controller, 280 const Message* request, 281 Message* response, 282 Closure* done) = 0; 283 284 private: 285 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcChannel); 286}; 287 288} // namespace protobuf 289 290} // namespace google 291#endif // GOOGLE_PROTOBUF_SERVICE_H__ 292