1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc. All rights reserved.
3// https://developers.google.com/protocol-buffers/
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: [email protected] (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 hypothetical "MyRpcChannel" as an example:
78// MyRpcChannel channel("rpc:hostname:1234/myservice");
79// MyRpcController controller;
80// MyServiceImpl::Stub stub(&channel);
81// FooRequest request;
82// FooResponse 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/callback.h>
105#include <google/protobuf/stubs/common.h>
106
107#ifdef SWIG
108#error "You cannot SWIG proto headers"
109#endif
110
111#include <google/protobuf/port_def.inc>
112
113namespace google {
114namespace protobuf {
115
116// Defined in this file.
117class Service;
118class RpcController;
119class RpcChannel;
120
121// Defined in other files.
122class Descriptor; // descriptor.h
123class ServiceDescriptor; // descriptor.h
124class MethodDescriptor; // descriptor.h
125class Message; // message.h
126
127// Abstract base interface for protocol-buffer-based RPC services. Services
128// themselves are abstract interfaces (implemented either by servers or as
129// stubs), but they subclass this base interface. The methods of this
130// interface can be used to call the methods of the Service without knowing
131// its exact type at compile time (analogous to Reflection).
132class PROTOBUF_EXPORT Service {
133 public:
134 inline Service() {}
135 virtual ~Service();
136
137 // When constructing a stub, you may pass STUB_OWNS_CHANNEL as the second
138 // parameter to the constructor to tell it to delete its RpcChannel when
139 // destroyed.
140 enum ChannelOwnership { STUB_OWNS_CHANNEL, STUB_DOESNT_OWN_CHANNEL };
141
142 // Get the ServiceDescriptor describing this service and its methods.
143 virtual const ServiceDescriptor* GetDescriptor() = 0;
144
145 // Call a method of the service specified by MethodDescriptor. This is
146 // normally implemented as a simple switch() that calls the standard
147 // definitions of the service's methods.
148 //
149 // Preconditions:
150 // * method->service() == GetDescriptor()
151 // * request and response are of the exact same classes as the objects
152 // returned by GetRequestPrototype(method) and
153 // GetResponsePrototype(method).
154 // * After the call has started, the request must not be modified and the
155 // response must not be accessed at all until "done" is called.
156 // * "controller" is of the correct type for the RPC implementation being
157 // used by this Service. For stubs, the "correct type" depends on the
158 // RpcChannel which the stub is using. Server-side Service
159 // implementations are expected to accept whatever type of RpcController
160 // the server-side RPC implementation uses.
161 //
162 // Postconditions:
163 // * "done" will be called when the method is complete. This may be
164 // before CallMethod() returns or it may be at some point in the future.
165 // * If the RPC succeeded, "response" contains the response returned by
166 // the server.
167 // * If the RPC failed, "response"'s contents are undefined. The
168 // RpcController can be queried to determine if an error occurred and
169 // possibly to get more information about the error.
170 virtual void CallMethod(const MethodDescriptor* method,
171 RpcController* controller, const Message* request,
172 Message* response, Closure* done) = 0;
173
174 // CallMethod() requires that the request and response passed in are of a
175 // particular subclass of Message. GetRequestPrototype() and
176 // GetResponsePrototype() get the default instances of these required types.
177 // You can then call Message::New() on these instances to construct mutable
178 // objects which you can then pass to CallMethod().
179 //
180 // Example:
181 // const MethodDescriptor* method =
182 // service->GetDescriptor()->FindMethodByName("Foo");
183 // Message* request = stub->GetRequestPrototype (method)->New();
184 // Message* response = stub->GetResponsePrototype(method)->New();
185 // request->ParseFromString(input);
186 // service->CallMethod(method, *request, response, callback);
187 virtual const Message& GetRequestPrototype(
188 const MethodDescriptor* method) const = 0;
189 virtual const Message& GetResponsePrototype(
190 const MethodDescriptor* method) const = 0;
191
192 private:
193 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Service);
194};
195
196// An RpcController mediates a single method call. The primary purpose of
197// the controller is to provide a way to manipulate settings specific to the
198// RPC implementation and to find out about RPC-level errors.
199//
200// The methods provided by the RpcController interface are intended to be a
201// "least common denominator" set of features which we expect all
202// implementations to support. Specific implementations may provide more
203// advanced features (e.g. deadline propagation).
204class PROTOBUF_EXPORT RpcController {
205 public:
206 inline RpcController() {}
207 virtual ~RpcController();
208
209 // Client-side methods ---------------------------------------------
210 // These calls may be made from the client side only. Their results
211 // are undefined on the server side (may crash).
212
213 // Resets the RpcController to its initial state so that it may be reused in
214 // a new call. Must not be called while an RPC is in progress.
215 virtual void Reset() = 0;
216
217 // After a call has finished, returns true if the call failed. The possible
218 // reasons for failure depend on the RPC implementation. Failed() must not
219 // be called before a call has finished. If Failed() returns true, the
220 // contents of the response message are undefined.
221 virtual bool Failed() const = 0;
222
223 // If Failed() is true, returns a human-readable description of the error.
224 virtual std::string ErrorText() const = 0;
225
226 // Advises the RPC system that the caller desires that the RPC call be
227 // canceled. The RPC system may cancel it immediately, may wait awhile and
228 // then cancel it, or may not even cancel the call at all. If the call is
229 // canceled, the "done" callback will still be called and the RpcController
230 // will indicate that the call failed at that time.
231 virtual void StartCancel() = 0;
232
233 // Server-side methods ---------------------------------------------
234 // These calls may be made from the server side only. Their results
235 // are undefined on the client side (may crash).
236
237 // Causes Failed() to return true on the client side. "reason" will be
238 // incorporated into the message returned by ErrorText(). If you find
239 // you need to return machine-readable information about failures, you
240 // should incorporate it into your response protocol buffer and should
241 // NOT call SetFailed().
242 virtual void SetFailed(const std::string& reason) = 0;
243
244 // If true, indicates that the client canceled the RPC, so the server may
245 // as well give up on replying to it. The server should still call the
246 // final "done" callback.
247 virtual bool IsCanceled() const = 0;
248
249 // Asks that the given callback be called when the RPC is canceled. The
250 // callback will always be called exactly once. If the RPC completes without
251 // being canceled, the callback will be called after completion. If the RPC
252 // has already been canceled when NotifyOnCancel() is called, the callback
253 // will be called immediately.
254 //
255 // NotifyOnCancel() must be called no more than once per request.
256 virtual void NotifyOnCancel(Closure* callback) = 0;
257
258 private:
259 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcController);
260};
261
262// Abstract interface for an RPC channel. An RpcChannel represents a
263// communication line to a Service which can be used to call that Service's
264// methods. The Service may be running on another machine. Normally, you
265// should not call an RpcChannel directly, but instead construct a stub Service
266// wrapping it. Example:
267// RpcChannel* channel = new MyRpcChannel("remotehost.example.com:1234");
268// MyService* service = new MyService::Stub(channel);
269// service->MyMethod(request, &response, callback);
270class PROTOBUF_EXPORT RpcChannel {
271 public:
272 inline RpcChannel() {}
273 virtual ~RpcChannel();
274
275 // Call the given method of the remote service. The signature of this
276 // procedure looks the same as Service::CallMethod(), but the requirements
277 // are less strict in one important way: the request and response objects
278 // need not be of any specific class as long as their descriptors are
279 // method->input_type() and method->output_type().
280 virtual void CallMethod(const MethodDescriptor* method,
281 RpcController* controller, const Message* request,
282 Message* response, Closure* done) = 0;
283
284 private:
285 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcChannel);
286};
287
288} // namespace protobuf
289} // namespace google
290
291#include <google/protobuf/port_undef.inc>
292
293#endif // GOOGLE_PROTOBUF_SERVICE_H__
294